# AMC7135 not regulating - hand soldered - Help appreciated. Stumped.



## eatkabab (Jan 10, 2012)

*Please skip down to "UPDATE"*



So I'm trying to use a single AMC7135 to operate an XRE/XPE at 350ma (single lithium 3.7v batt). I've followed the wiring diagram below and used two different AMC7135's to test. I can't seem to get it to regulate anything at all. With the 7135 in circuit, it's as if the battery is directly running to the LED.

Circuit that was followed:







Test circuit 1 (XRE): - no capacitors, just for quick testing






Test circuit 2 (XPE): - one capacitor added




Voltage testing from the (+) pin of the LED to the GND pin of the 7135 also measured at 3.65v.


I would have tested current, but I usually don't use that function so I don't remember how to set it up. Regardless, at 350ma, an XPE should be operating near 3.0v. When I directly connect the batt to the LED, it appears to be just as blindingly bright. When attached to a 350 buck regulator it's not as blinding.


Such a simple circuit. I'm clueless! Why isn't it working?
Thank you very much.




*UPDATE:
*Okay so I took everything apart and resoldered and retested (this time I was actually awake). You can see the results below:




It turns out the AMC7135 is regulating just fine. Turns out the LED is just brighter than I anticipated at 1watt. However I did learn some interesting things during my testing.




- First of all, the capacitor seems to do nothing. Is it really necessary? Could it possibly increase efficiency?

- On the XPE R3, it seems the higher the input voltage above the Vf, the lower the output current of the AMC7135 (350 +/-25). As if the regulator is almost trying to be more efficient. Possible?

- The AMC7135 works very well with the XPE R3, but it outputs 0.370A when on my XRE R2 (plus ~0.2v higher) regardless of input voltage. I know the XPE is more efficient and requires lower Vf, but does the LED being less efficient cause the AMC to be less efficient also? Not sure why it's so far off from 350ma.

- I was previously using an AMC chip that I had soldered and resoldered maybe a dozen times. This particular chip may have been fried and was consistently producing 0.40A...?

- Lastly, If I'm going to use a low voltage CMOS 555 timer with a couple resistors to achieve PWM, I still need a transistor right? Any idea how much power this will consume? Will a 70% duty cycle increase potential run time off the pair of parallel 18350 batteries I plan to use? Or will the PWM circuit eat up a considerable amount of energy?

- LAST lastly, would there happen to be a 250ma version of the AMC7135...AMC7125? Some searching came up dry.



Thank you all, and I apologize for my originally half-wit tests.


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## moderator007 (Jan 11, 2012)

I dont think you need the capacitor, all the plain no mode boards dont have one. I studied this wiring for awhile and it looks like you have it correctly wired if the red and black wires are your source voltage. I dont know what that extra wire is hanging of the led negative. What is your source voltage?

To check the current you will have to set your DMM to current. Usually by moving the positive lead to another hole that reads 10A or 20A on the DMM. Then set the dial to amps (A). You want to measure current as it flows through the wire so it has to be in the circuit just like it was another led hooked in series with the one you have. The current has to flow threw the DMM to the led. This measures the actual current the led is seeing. Here's a good thread on using a DMM for measurements.


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## MikeAusC (Jan 11, 2012)

It seems like the 7135 is shorted input to output.

The soldering limits are 260 deg for 10 seconds - exceeding this could damage the 7135, as could static.


Then again, looking at test circuit 2, both the white and the blue arrow seem to point at the + wire ???

You should be leav[FONT=Verdana, Arial, Helvetica, sans-serif]ing the Multimeter Red lead on the red battery wire and moving the Black Multimeter probe between the Battery black and the LED-.[/FONT]


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## eatkabab (Jan 11, 2012)

MikeAusC said:


> It seems like the 7135 is shorted input to output.
> 
> The soldering limits are 260 deg for 10 seconds - exceeding this could damage the 7135, as could static.
> 
> ...




So yeah the left white/blue on the red/(+) lead. I'm just moving the (-) lead reading. The red/black is coming directly from the batt which is a single 18650 cell reading 3.65v.

So now I'm thinking that the current is regulated down to 350ma but the LED is pulling higher voltage? Even if, the maximum wattage would be 350*3.65 = ~1.2watts if the AMC is working and it looks to be as bright as full 3.3watts. I'm going to test the current when I get a chance but these measurements aren't promising. 

I don't think I've shorted the AMC7135 because my crappy soldering iron probably can't even get to 260C. My next test is to run multiple LED's in series... But I still have no idea why it's not working.


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## CKOD (Jan 11, 2012)

eatkabab said:


> So yeah the left white/blue on the red/(+) lead. I'm just moving the (-) lead reading. The red/black is coming directly from the batt which is a single 18650 cell reading 3.65v.



Your moving the - lead to a different point on the same wire. Measure across the LED at the "OUT" pin, not the ground pin.


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## b-bassett (Jan 11, 2012)

as mentioned above, im not sure you've tested at the correct points. the ground pin of the reg is the same point as the black power lead ( just diff end of short wire) so you will never get a different reading.

try re-testing but this time measure voltage across these exact points 

1. cell +ve to -ve
2. led +ve to -ve

this should show you if theres any regulation happening. (assuming the xpe you have runs at 3V for 350mA)


as a further test for proof, you could cut the cable supplying vdd to the reg chip, this should switch the reg (+LED) off and will test the switching potion of the reg

another thing to note, is that the chip needs at least LED voltage + 0.7V ( i think) to regulate properly. 

also if you want to add more LED'S in series you will need more input voltage, (though dont go over 6V to the reg)


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## moderator007 (Jan 11, 2012)

b-bassett said:


> another thing to note, is that the chip needs at least LED voltage + 0.7V ( i think) to regulate properly.


I think its about .15v drop out.


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## Justin Case (Jan 11, 2012)

You can't go by visual impression as to what the LED drive current is. Bare power LEDs all look blinding even at relativly low drive.

Measure your LED Vf across LED+ and LED-. Measure your battery current draw by putting the DMM in series with the batt (of course, the added resistance could affect things, but hopefully you have enough voltage overhead to avoid misleading results).

At 350mA drive, the datasheet claims an XP-E could have a Vf of around 3.2V. An XR-E could be around 3.3V. So in theory, you that's about what you should be measuring. For battery current draw, you should measure something close to 0.35A.


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## b-bassett (Jan 12, 2012)

moderator007 said:


> I think its about .15v drop out.



i did think my estimate was a lil high, but for some reason 0.7 is stuck in my head, must be from the protection diode or sumthing?


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## eatkabab (Jan 13, 2012)

Okay so I took everything apart and resoldered and retested (this time I was actually awake). You can see the results below:




It turns out the AMC7135 is regulating just fine. Turns out the LED is just brighter than I anticipated at 1watt. However I did learn some interesting things during my testing.




- First of all, the capacitor seems to do nothing. Is it really necessary? Could it possibly increase efficiency?

- On the XPE R3, it seems the higher the input voltage above the Vf, the lower the output current of the AMC7135 (350 +/-25). As if the regulator is almost trying to be more efficient. Possible?

- The AMC7135 works very well with the XPE R3, but it outputs 0.370A when on my XRE R2 (plus ~0.2v higher) regardless of input voltage. I know the XPE is more efficient and requires lower Vf, but does the LED being less efficient cause the AMC to be less efficient also? Not sure why it's so far off from 350ma.

- I was previously using an AMC chip that I had soldered and resoldered maybe a dozen times. This particular chip may have been fried and was consistently producing 0.40A...?

- Lastly, If I'm going to use a low voltage CMOS 555 timer with a couple resistors to achieve PWM, I still need a transistor right? Any idea how much power this will consume? Will a 70% duty cycle increase potential run time off the pair of parallel 18350 batteries I plan to use? Or will the PWM circuit eat up a considerable amount of energy?

- LAST lastly, would there happen to be a 250ma version of the AMC7135...AMC7125? Some searching came up dry.



Thank you all, and I apologize for my originally half-wit tests.


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## MikeAusC (Jan 13, 2012)

If you use the 555 output to drive the Vcc input of the 7135, it will draw very little power. 

PWMing the drive is very efficient - 50% PWM will mean about 50% power consumption.


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## Justin Case (Jan 13, 2012)

eatkabab said:


> Okay so I took everything apart and resoldered and retested (this time I was actually awake). You can see the results below:
> 
> 
> 
> ...



The cap isn't absolutely necessary. The datasheet says:

Output Capacitor CO and PCB layout:
The output capacitor CO may be removed under certain condition. Please refer to the following figure. If LED and
AMC7135 is located in the same PCB, and the length of the routing path L1<10cm & L2<3cm, the output capacitor CO
can be neglected.

Maybe the XP-E sees lower drive current because the 7135 is getting hotter vs when you use the XR-E. 7135 efficiency is Vload/Vin. So paradoxically, efficiency is lower when you use a low Vf LED. The higher you raise the input voltage above Vload, the worse the efficiency. Seems doubtful since you have the 7135 in air and the difference in XP-E vs XR-E Vf is probably not that much. If the 7135 were heat sinked, I would think you might see a thermal effect. But without a heat sink, I'd suspect that the 7135 heats up quickly in either case. But who knows. Maybe the actual Vfs differences are greater than what the datasheets suggest.


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## degarb (Oct 31, 2016)

5 square cm to heat sink? Problem more if using same sink as led. . Seems most of these convoy style single 18650 aren't set up correctly for 700 ma, much less their 2.8 ma. 

Does the Co go (longer than 4 inches) between the battery +/-? . Wouldn't that short out the simple circuit? Even if electric flowed in only one direction through the cap? 

Did any one find a pwm that can limit the amc7135 and be ramped with a potentiometer? . I hate, hate, hate, hate clicking. . Also want infinite control, Max of 1 watt per 18650. I can compromise on the clicky, but not the ban on multiple AMC or infinite AMC control.


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## Dr. Mario (Oct 31, 2016)

It is impossible to control the current across AMC7135 via the potentiometer as it is regulated by internal Zener diode voltage reference - however if you're a bit insane, PWM is your best bet. Microcontroller or 555 timer is your best friend in managing the LED current. 555 timer is however much simple that a caveman can use it.

As for clicky, no matter how much you hate it, it's the battery's only savior. Simply put, if you remove the switch from the circuit, what will happen to the battery? You will discharge the Lithium-ion battery past the dangerous discharge threshold (although with AMC7135, it's unlikely as it simply shut down at 2.8 Volts). So it's obviously better to have switch of some type (even rocker switch) to prevent accidental discharge when it's not being used.


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## degarb (Oct 31, 2016)

Dr. Mario said:


> It is impossible to control the current across AMC7135 via the potentiometer as it is regulated by internal Zener diode voltage reference - however if you're a bit insane, PWM is your best bet. Microcontroller or 555 timer is your best friend in managing the LED current. 555 timer is however much simple that a caveman can use it.
> 
> As for clicky, no matter how much you hate it, it's the battery's only savior. Simply put, if you remove the switch from the circuit, what will happen to the battery? You will discharge the Lithium-ion battery past the dangerous discharge threshold (although with AMC7135, it's unlikely as it simply shut down at 2.8 Volts). So it's obviously better to have switch of some type (even rocker switch) to prevent accidental discharge when it's not being used.



In layman terms, what is needed for the 555 setup. 

I concede I am licked, must use my clickies. It is really that of all the lights ever made, probably 1 percent have proper run levels: workday, two workday, half workday, workweek. . In this order of importance. . Easiest thing is one workday, plus an infinitely dimmable wheel for 1 to 20 workdays. . But give me one AMC and some pwm lower levels for an edc, I will be happy, for a while, at least. 

I figured out why I see early dimming with my 2, or so, AMC 7135, probably near 3.5 volt mark, even at the 30 percent pwm . . Again, poor design. My two convoys are 2.4 amp, pwm. . So, the forward voltage at 2.4 amps is 3.2v, need 3.4v-.2v above fwd voltage. . Tired of feeding a Convoy two 18650s a day on an edc tgat I use maybe 2.5 hours on 800ma-due to the greedy setup and other factors. So, the edc I wish to build will have one AMC, and a dimmer. A throwy xpl hi in a 35 or 31 mm smooth with AR glass. 

So, I need to know the 555 setup details :Source, other components and layout. And I can use short or super heavy wire to avoid the capacitors for the amc. . Yes, I see why they may be necessary, but no one has stated the consequences. I understand how I line a cap may help, only if inline. The amc7135 is far more fragile than the buckpuck that I have used in many lights, maybe no cap will damage the chip on long skinny lines. But what about 8 gauge wire?


Also, the 555 sounds more like fun than just desoldering AMC s off other boards.


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## Dr. Mario (Oct 31, 2016)

555 timer chip's output can be fed into the Power-on pin on AMC7135 regulator. As for 555 timer design, there's online 555 calculator, or if you use Android phone, it's also available on Play Store. Configure it the way you like, and then breadboard the whole thing to ensure it works the way you intend.


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## degarb (Nov 1, 2016)

Dr. Mario said:


> 555 timer chip's output can be fed into the Power-on pin on AMC7135 regulator. As for 555 timer design, there's online 555 calculator, or if you use Android phone, it's also available on Play Store. Configure it the way you like, and then breadboard the whole thing to ensure it works the way you intend.



No time for a while, to dedicate more than 10 minutes, here and there. 
. . But, people are using pots and the 555 to run leds from 10 percent to 90%. . Assume, then, it could be used for the AMC. . I would actually be happier with 90% of 340 ma than 340ma.

Few webpage, or videos, were very good at explanations or meaning. Doubtful they understood it themselves. Just genius at blindly following directions. . But two videos make it clear! . Got enough of Clive's video to get it, and plan to finish another day when less business going on. Links below. . Still, I may need part sourcing vendor list. And, specific pot schematic for the Amc7135 set up. 

https://youtu.be/WqGq9Yv1d_U

https://youtu.be/SX01x1z7fTY


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## DIWdiver (Nov 1, 2016)

'555s have been around since the '70s, and still a useful chip. Amazing!

Unfortunately, I haven't seen one that can switch more than about 200 mA, and since the AMC7135 doesn't have a power-on pin, you'd have to find another way to switch the full 350 mA (or more if you use multiple chips).

Fortunately, it's quite easy to add an FET between the '555 and the driver. The FET would take the low-current output from the '555 and switch the high current driver on and off. This is what '7135-based drivers do to achieve various modes. The '7135 itself is just a constant current regulator; a microcontoller and FET are added to provide dimming and blinking/flashing features.

My favorite place to buy electronic parts is DigiKey.com. AFAIK they have the best search tool in the world. They stock over a million different components, and ship within hours (same day if you order by 8:00 PM) (Yes, that's PM). They often aren't the cheapest, but they'll ship small packages USPS for under $3.00; that often makes up for it on small orders. Good competitors in the US include Mouser, Arrow, Avnet, Newark, and others. Any of them should have everything you need except the '7135. I couldn't find a US distributor that stocks it.

You need to be careful selecting a '555. They are not all the same and many will not work well (if at all) below 4V. Same for the FET. I'm happy to help with part selection if you need it. I'm sure others are as well.


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## degarb (Nov 1, 2016)

Diwdiver! Yes. A schematic, specific to driving one led, via 1 AMC, via 555, using a 5 k pot. . And tech support, sourcing help if get stuck. Post here for others. . Pm me if new thread. . 

Capacitor choice, I would think be pre-established. 

Not sure how far off this schematic is : http://www.instructables.com/id/Very-simple-PWM-with-555Modulate-every-thing/ still seems off to me. .


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## degarb (Nov 2, 2016)

Yes, that instructable, in my last post, seems like a teen extra credit report. The schematic, photocopied from a 1981 ee textbook.

So, my gut tells me the following will work (your thoughts?):

http://www.instructables.com/id/Yet-Another-Simple-Pot-controlled-555-PWM-generato/


Components (vendor rec?):
* 1 - Generic 555 IC (NE555 was used) (Brand?)
* 2 - 1K Resistors (R1, R3)
* 1 - 100K Linear Potentiometer ( R2 = 100 * R1 )
* 1 - 1n4004 Diode (Pretty much any diode will do)
* 1 - .1uF Ceramic Capacitor (Unsure about the relation of the value of this to the resistors)
* Breadboard


















Also, my heart sank, when the 4.5 volt minimum spec was raised. But further research, shows this isn't true. http://www.electroschematics.com/6923/555-low-voltage-operation/
Though using the 18650 voltage, might change the r1 and r2 value, maybe the cap value? Though, r3 seems unnecessary since you have a pot behind it. But I know little yet, anyway, at this point.


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## Dr. Mario (Nov 2, 2016)

DIWdiver said:


> '555s have been around since the '70s, and still a useful chip. Amazing!
> 
> Unfortunately, I haven't seen one that can switch more than about 200 mA, and since the AMC7135 doesn't have a power-on pin, you'd have to find another way to switch the full 350 mA (or more if you use multiple chips).
> 
> ...


Odd. I thought the datasheet mentioned power control pin in AMC7135 LED regulator. I will look again.

And I didn't have had a chance to quickly put up an example because the Everycircuit author tried to charge me twice for what I already paid for on Play Store... Oh well, paper and pen is still the simplicity. DIWdiver, you have me beat.


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## Dr. Mario (Nov 2, 2016)

I think I misread the datasheet, you're correct. From my observation, some LED drivers tie Vdd of the AMC7135 to the microcontroller pin, while LED is wired through from the AMC7135 to ground.

And as for 555 timer selection, I agree.

EDITED: Lastly, here we wouldn't care about the frequency (although we would ideally try to run it at 20 kilohertz or higher to mask the whining or hissing sound of the AMC7135 being PWM'd), just the duty cycle that determine brightness - 10% = quite dim / 100% = quite bright - you get the idea.


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## DIWdiver (Nov 2, 2016)

I hadn't thought of putting PWM on the Vdd pin. That might work very well, and would eliminate the FET.


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## DIWdiver (Nov 2, 2016)

degarb said:


> Yes, that instructable, in my last post, seems like a teen extra credit report. The schematic, photocopied from a 1981 ee textbook.
> 
> So, my gut tells me the following will work (your thoughts?):
> 
> ...



This should work quite well. 

One of the beautiful things about this chip is that its behavior is almost completely independent of supply voltage, over quite a wide range. The diode is the gotcha there. At low voltages, it starts to be pretty significant. I think to run it on a single cell, I'd want a schottky diode there. Something like the LSM115JE3 would be ideal. Most don't have as low a voltage as that one.

The frequency is determined by the product of R1+R2+R3 and C. The larger that product is, the lower the frequency. In fact it's inversely proportional. So doubling C cuts the frequency in half. Dividing C by 10 multiplies the frequency by 10. You could do the same with the resistors, but R1 and R3 shouldn't be much lower that 1K, and the total shouldn't be more than 1M (1000K) or so. There's a lot more latitude in changing C. If I recall correctly, the values here should give you a frequency of about 170 Hz. 

The maximum duty cycle is approximately (R2+R3)/R1. The minimum duty cycle is approximately R3/(R1+R2). Given the values presented here, that's about 0.99 and 0.01, or 99% and 1%. So it's easy to adjust the max and min brightness by changing R1 and/or R3 (they don't need to be the same).

I think all '555 type timers can run well over 20 kHz, but I don't know about the AMC7135. Maybe some experiments are in order?

Assuming you want surface mount, here's a good part to use: ICM7555CBAZ. If you want through-hole or fine-pitch SMT, ask and ye shall receive.

I'm guessing any flavor of the ICM7555, LMC7555, TLC555, and some others would work, but that first one is the only one that I verified by looking at the datasheet.


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## degarb (Nov 2, 2016)

I assume 170 is a good value. . Probably will have at 99 percent when hand working. . Navigation by walking and reading, lower. . Other lights the pwm only detectable on low with hand wave. 

Now, the tiny 2m sot-89 are available at fasttech.com and Intl-outdoor the 6mm to--252 only found on alibaba. 

Probably, not surface mount, I am thinking clustered behind a heat sink. Amc7135 heat sink ed. . The most compact I can get. . Maybe a slider pot. Good switches have been the Achilles of my builds in past.


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## degarb (Nov 3, 2016)

DIWdiver said:


> The diode is the gotcha there. At low voltages, it starts to be pretty significant. I think to run it on a single cell, I'd want a schottky diode there. Something like the LSM115JE3 would be ideal. Most don't have as low a voltage as that one.



Is this lsm115je3 the smallest? The pict looks big. off to pull up specs.


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## degarb (Nov 3, 2016)

degarb said:


> Is this lsm115je3 the smallest? The pict looks big. off to pull up specs.




Looks small enough, from drawing.

Okay, I ordered from digikey. First time ever, where the checkout price said, "Price Unknown"

They didnt have any amc7135s. I really wish I could get the to--252 version. I don't like alibaba format. I only bought one headlamp from a vendor on alibaba. The driver burned out in 3 hours of use. The led color horrid.


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## degarb (Nov 4, 2016)

Did a new test circuit to LED. (DigiKey 555 components not in, but wanted to test other things) . . I did another AMC, soldering with lead syringe solder, using extra, extra strong reading glasses. . This time I soldered the left negative on 1cmx3cm copper flashing for heat sink. (Copper sheets are insane, but solderable and conductive, so essential for playing with builds.) This time, I tested with my 2 (or 20?) mega ohm pot on only vdd. . At first I could dim to 100ma from a full 380ma. I soldered it up, and then, alas, it would go from 380 down only a tad, then, shift into direct drive of led!!! . . I got freaked out, worried I would burn out the only led and AMC before next shipment. . Desoldered, and now all is working as expected.... I am shocked how hot the copper sink is getting off 4.2 excess burnout!! . . My pot and Resistors don't seem to get this hot in dd. . Also, those poor amcs on those AMC cluster boards on small lights running at many many watts.

I may need a much lower pot to get any meaningful dimming. If this is possible, that is, without the 555 pwm. . Fewer components are fewer points of failure. Though the 555 route looks easy, and cheap enough, to me, at this point. Also the 555 could be used on buck drivers perhaps?


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## degarb (Nov 4, 2016)

Also, I purposely left l1 and l2 too long, with no Capacitors. . My reading lead to ee pages recommend all chips be protected by this exact. 1uF on either side, against voltage spikes. . If they are parroting good ee practice in specs, rather than real issue correction, then I don't see how a DC 18650 could spike and damage chip. . Could it? . Only ran the new chip for half hour then left. . Saw same 380 ma on 3.5 v cell as 4.2v. No, drop in half hour. 

My Dmm reads temp, but short in probe. Are they STANDARD? Can I buy more? . Or do I need to deinsulate and solder up the old ONE? . Not sure of exact construction of dmm temp probe.


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## DIWdiver (Nov 4, 2016)

degarb said:


> My Dmm reads temp, but short in probe. Are they STANDARD? Can I buy more? . Or do I need to deinsulate and solder up the old ONE? . Not sure of exact construction of dmm temp probe.



If it's a thermocouple, there are standard temperature probe connectors, which are pretty common. There's a standard and a miniature version. They are color coded to tell you which thermocouple type they are for. The most common one is the K-type with miniature connector, like this https://www.amazon.com/dp/B00OK6CBMU/?tag=cpf0b6-20. If you get a probe with the right color connector and the right size, it should work.

A thermocouple is formed any time two different metals come in contact. This generates a small voltage that's roughly proportional to temperature. This is highly dependent on what alloys are selected. Over the years a handful of alloy combinations have become very popular, as they work out to have beneficial properties. These are referred to by a single letter, such as B, E, J, K, and T. The most common type is two wires, one of each alloy, which are welded together at the tip and insulated from each other everywhere else. The same alloys are used for all the connections all the way back into the meter.

This means that a thermocouple probe should appear shorted if measured with an ohmmeter. A K-type thermocouple at room temperature generates about 1.3 millivolts. At 100C, it's 4.5 mV.


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## degarb (Nov 4, 2016)

Thank you so much. . That Amazon link looks a dead ringer to mine. 

I can report here that I finally killed my amc7135 by using the pot on vdd. . I found two more pots and could not help myself for another test or three The 25 ohm pot did nothing, but it seems the 25k ohm pot did it in. . Perfect dimming for first knob turn or two, then it turned the led back on, letting at least 1.5 amps go from led negative in the amc7135 and out to battery. This 1.5 amp for enough seconds killed the amc7135. .... Now, maybe 250 ohm pot might be the sweat spot to retard but not kill, maybe a little higher. Yet to test.. .But do know the vdd needs to be on-hand some voltage - to suppress current going through. . I probably will personally pass on sacrificing and more chips, or buying more pots for more attempts - albeit indication seems there my be some safe range. 

Are there only Asian vendors of the amc7135 chip? I am down to two. . They are fragile and I killed three so far. I need to reup. Probably easy to drop and loose one too.


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## degarb (Nov 5, 2016)

You wrote: "The FET would take the low-current output from the '555 and switch the high current driver on and off. "

Still, no parts to test with, but since my test showed that quash of the vdd alone, may kill the amc7135. Thus, I may need this fet after all. ... Now, what does that entail?


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## degarb (Nov 5, 2016)

degarb said:


> You wrote: "The FET would take the low-current output from the '555 and switch the high current driver on and off. "
> 
> Still, no parts to test with, but since my test showed that quash of the vdd alone, may kill the amc7135. Thus, I may need this fet after all. ... Now, what does that entail?



http://www.mtnelectronics.com/index.php?route=product/product&path=25&product_id=213
??


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## DIWdiver (Nov 5, 2016)

degarb said:


> http://www.mtnelectronics.com/index.php?route=product/product&path=25&product_id=213
> ??



That would work okay in your application. I like the DMG6968U better though. It's smaller, cheaper, and in this application, would actually work better.

Nothing against MTN, but you can get the IRLR8726 a lot cheaper at Digikey. I don't know what shipping is from MTN, but from DK you can choose USPS, under $3.00 for small packages.

A FET, which in this case we have shortened from "N-channel MOSFET" (there are other kinds of FETs, but N-channel MOSFETs are the most common) can operate in either of two modes: Saturated or Active.

In the saturated mode it's essentially a voltage controlled switch. You apply voltage to the Gate, the Source and Drain pins are shorted. No voltage at the gate, the source and drain are open.

In the active (also sometimes called linear) mode, it acts like a voltage controlled resistor. Voltage on the gate controls resistance between source and drain. This is used in many linear current regulators, including the AMC7135. In the '7135 there's a sense resistor, and a circuit that adjusts the voltage on the gate of a FET. If the current is too high, the gate voltage is reduced; if it's too low the gate voltage is increased. In this way the resistance of the FET is constantly adjusted to be just the right value to get 350 mA through the sense resistor (and your LED).

Really the only difference between active and saturated modes is how we drive the gate. Once the gate voltage is high enough, pushing it higher has very little effect on the resistance of the FET, and we consider it saturated. When selecting a FET for use as a switch, we need to make sure that the voltage we have to drive the gate (in this case 2.7-3.0V at end of battery life) is enough to drive it into saturation. Also keep in mind the the '555 can't drive its output all the way to the power supply. You loose something like 0.4V IIRC.

The transition from active to saturated is gradual, and depends on the current through the device. At 350 mA, the IRLR8726 starts to saturate at around 2.6V, and is well saturated at around 3.0V. The DMG6968U is well saturated at 2.0V.

To use the FET in this application, I would connect source to ground, gate to the '555 output, and drain to the '7135s GND pin. The '7135 VDD pin is connected to battery+, and the LED between battery+ and the '7135 output pin.


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## degarb (Nov 6, 2016)

DIWdiver said:


> The DMG6968U is well saturated at 2.0V.
> 
> To use the FET in this application, I would connect source to ground, gate to the '555 output, and drain to the '7135s GND pin. The '7135 VDD pin is connected to battery+, and the LED between battery+ and the '7135 output pin.




Dmg, it is then. The hookup is backwards from my initial guess. 

Very clear explanation, diwdiver! . I had to reference sparkfun to refresh my 10th grade electronics. I still have an urge to put a vacuum tube in there somewhere. 

Now, what is your opinion on the amc7135 v. A buck driver?.... My calculations 3.7 volt average 18650 with 2.75 fwV, imagining 42 point one, .1, volt, 3200mah, cells cycled to rest, make a simple humanly managed 25 ohm pot resistor, 75% efficient. Now, Buck drivers are 90%. Sure a 8xamc at 3 amps and 3.6 fwV is 90%, but at the 350ma, my bet is 75 to 80% efficient. The amc7135s are obviously creating much heat, as I can see with mine soldered onto 3 Sq cm of copper flashing. Ten percent efficiency is huge, when I am building a single Xp-l hi 35mm reflector at a max of 350ma, 1%-99% control. . Means, I can get 4500 candela for or 9 hours, and that 10 percent is a precious hour. . I was thinking I might save the FET/pot/ 555 for the intl-outdoor.com buck, or some buck at mtnelectronics. I think that intl-outdoor.com has an easy to swap reference resistor that could be raised to make a max current of 350ma. Though I might accept a max of 700ma. I think the shunt/reference resistor value range is too low for a pot, and these low 3 volt buck drivers don't have any built in voltage reference pin, I believe.... So far, all bucks I have seen have too high voltage dropout or too high current-- useless settings for real world use. Great wow factor. . But I need a wow factor but once a year, and that wow current setting has a daily price tag (which now is not place to debate) .


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## DIWdiver (Nov 7, 2016)

Back when I started, Vf was too high for a single LiIon cell to run very well. Then it came down, and linear drivers were awesome, even better than bucks in many cases. Now it's getting so low that bucks are starting to look better.

The efficiency of any linear driver is dead simple to calculate: Vout/Vin. It's actually slightly lower than that because of ground pin current (often called "quiescent' current), but that's often trivial. You can move the losses among various components, but when looked at as a whole, the equation holds.

So no matter what you do to it, a '7135 based driver is not going to impress with efficiency on a LiIon cell and an LED with Vf of 2.75V, averaging about 74%. But it should regulate right down to 2.9V.

It's a challenge to get a buck regulator to stay efficient as the input voltage gets lower and lower. While it should be possible today to build one with 90% efficiency down to 3V input, I doubt it would be simple or cheap, unless someone has integrated all the necessary stuff in one chip. I'm not aware this has happened, but I haven't really looked.

I would say I'd have to look carefully at a particular buck regulator and the LED to see if I believed it would actually perform better than a linear on a single cell.


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## degarb (Nov 8, 2016)

Thanks, diwdiver 
I just added http://www.digikey.com/product-detail/en/diodes-incorporated/DMG6968UQ-7/DMG6968UQ-7DI-ND/5721506 to cart. Will need to do on desktop later, as quantity not working on phone.. I have realized in last 2 nights, in addition to current discipline and efficiently, with an edc, I am just too tired to wrestle with removing cell and charging it every few nights. DigiKey has a $7.99ISH CCCV MICRO USB I can build into my next light. http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=211344515&uq=636142321061953276

I also want to build a snake light for my son, as he need a bedside light and a neck light. Age 10 so can get my artist wife to do skin. . The single amc7135 555 pot is good enough for him. Will get him to help with the electronic soldering and schematics. p
For my edc, I want give the ld-4b buck a Crack to lower the sense by increasing it to .2 ohm then 555 fet it? I can live with 350 to 700. Though 400 really is shortest runtime I really appreciate. They don't state efficiency, and skill needed to build an efficient buck... I probably should call mtn since they can custom build a 5v buck. 5v ain't gonna work, but maybe we can give each other ideas. . I use the dimmable buckpuck 700 for my 2 cell lights, and fits my needs too perfectly to change. . It's this single cell driver issue I want to fix to bring in line for real world etc use, where runtime with brightness matter again. Not, either or. 


I am guessing that ccc-link above-v is best deal? I also need, before finalizing my DigiKey order, to do more reading as to better spec best ohm candidate for the ld-4b swap. .if I can get exactly 380ma, then I can head to head it against the amc7135. . No amc7135 at DigiKey, darnit. Hope I am mistaken. But, mtn electronics has both, amc7135 and ld-4b. But, they have no cccv usb boards.


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## degarb (Nov 8, 2016)

Also, has anyone actually tried 555 on the vdd, and had success? I am down to 2, so holding off trying to strobe that pin alone, until I get the DMG6968U. .


I am also wondering how the recommended caps on the amc7135 would affect this 555 setup?


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## degarb (Nov 10, 2016)

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=211487371&uq=636143640123482390

ThisPRT-10217 $8 board is based on the 60 cent MCP73831 chip http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=211490570&uq=636143640123492391 

http://ww1.microchip.com/downloads/en/DeviceDoc/20001984g.pdf plus caps and resistor. Naturally, you can do more with the raw chip at the lower price than with the complete board. Like, build into the light using a smaller space. Like, build your own 12 bay charger without breaking the bank. But for me, I would need to actually read the whole pdf, plus some outside reading, before knowing what stat and vss means.


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## degarb (Nov 13, 2016)

I finally got the 555 kit, minus the transistor. (yet more shipping charge)

Biggest problem is that I cant figure out the north south orientation of the 555. It looks nothing like the wikipedia, where there is a dot or two in the north side. There is random number on it too small to read. I could assume they would print north to south. Or I could assume they would print south to north.


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## degarb (Nov 13, 2016)

I also don't understand the pot wiring based on the schematic, if I do figure out which pin is 1 without frying chip. 

My best guess is Vs (through R1) and pin 7 go into center pin of pot. Out on pin 3 of pot. While pin 1 not hooked up.


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## degarb (Nov 13, 2016)

The diode orientation can be determined by my dmm.

I vaguely remember, I recall this capacitor is non polarized, so don't need to worry about orientation. http://www.instructables.com/id/Yet-Another-Simple-Pot-controlled-555-PWM-generato/


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## degarb (Nov 13, 2016)

degarb said:


> I finally got the 555 kit, minus the transistor. (yet more shipping charge)
> 
> Biggest problem is that I cant figure out the north south orientation of the 555. It looks nothing like the wikipedia, where there is a dot or two in the north side. There is random number on it too small to read. I could assume they would print north to south. Or I could assume they would print south to north.




http://www.intersil.com/content/dam/Intersil/documents/icm7/icm7555-56.pdf
But I'll be dipped, if there is any such divot in my chips to denote the north. Am I supposed to guess where pin1 is?


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## degarb (Nov 13, 2016)

Took a guess, wired the 555 up. (think I assumed writing went top to bottom, but don't quote me.) I didn't bread board, nor have I optimized wire lengths. I must say it was easy to get confused what to wire, and what had been wired. I was surprised, to see it light up the led and dim it to very little. I knew it was a less than 50% chance it would work.

I measured the milliamp range. Then I dismantled to test two other crummy drivers and a .3 ohm plus 25ohm rehostat pot: the buck, ld-29 cut out at 3.4 volts (so, I will throw it away); the 800 ma fasttech one failed to work at all; the rehostat did 20 ma to 600 ma on 3.5 volts.

I did not test on the amc7135 vdd, since from what I know, I am 100% sure pwm that pin will kill the chip. But am only 90% sure, that I know what I know.

I do not have a transistor on hand, no vacuum tubs; and, I failed to measure voltage out of the 555. I am unsettled the pwm 555 amps seemed to be only .5 ma to 6 ma. Yet, the led seemed to be more like 60 ma. So, maybe I measured the ma wrong. Maybe. 

I will need to study the wiring more to see how small I can get it. I have not yet tried to optimize space. Can this 5.2 mm chip even be put on a breadboard?

LOL! Just show what I think of you'alls battery vampire drivers:
LOL!





and I think my camera cut off some of the wires and connections.


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## degarb (Nov 13, 2016)

Got be something better than the drivers high end makers are stuffing into today's lights and calling it a useful driver. Been googling, still no pwm boards have I found. Only wow factor drivers. These look interesting: http://www.intersil.com/en/products...B_52AGeDZ_CBvwZMock_BPYYQL6I_8lr7oaAnFR8P8HAQ

But, I can relax if I can get a practical 555 package. If I can't find a buck that doesn't go wanko below 3.5 volt. I will use it to master a single amc7135, add a second switch to kick in an additional regular, straightup 7135. This will get me infinite variability between 3 ma and 800 ma. A lower cutout than the regular multi amc board (longer runtime), higher led efficiency (brighter at 350 and 700ma). I will still be locked in at the amc's 75% electrical efficiency (the same as a manual pot), but the benefit of constant current and no accidental high current incidents (which are huge in sucking down needed cells). 


*(like these 6xamc7135 with %75 efficiency at 350 ma, cutting out at %75 of a Panasonic discharge curve, slamming led 2.4 amps pwm to 340ma for %75 led efficiency at 2.4amps=.75*.75*.75 efficient for a real world).


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## degarb (Nov 14, 2016)

http://www.intersil.com/content/dam/Intersil/documents/icm7/icm7555-56.pdf

To me, looks like the pin spacing is 1.25 mm. Bread board hole spacing is double that? 

Is my 555 choice too small?


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## degarb (Nov 16, 2016)

Diw, would https://www.fasttech.com/products/0/10013209/2225900-risym-m7-smd-1n4007-1a-1000v-diode-50-pack
work. I am also thinking it might be a good idea to put in a diode for reverse polarity.

Now, back to the bread board issue. pin 6 splits out into like 3, 7/1/8/ into two, so bread board cut to size might work best. But the 1.27 mm spaced bb is 31 dollars at digikey! I think 2 mm spaced board are like $7. I see 5.2 mm and 7.6 mm 555's on digikey. I may have better luck with the larger 555s on breadboard? The youtube idea of using a marker and hydofloric acid and some copper circuit board looks good. I haven't researched parts on this method.

While it was fun building the working 555, I am not sure I can beat the size of this: https://www.fasttech.com/products/5376200
Not sure why 6 hookups. I can see +- in and out hookups, at most. Looks like 2 555 chips on board. Then again, maybe I want this one: https://www.fasttech.com/products/1005/10024820/5380400-0-10v-to-0-10khz-voltage-to-frequency-f-v voltage to pwm means nothing to me. neither does voltage to frequency. As far as I know, pwm keeps the voltage, just lowers the current through pulsing.


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## DIWdiver (Nov 16, 2016)

As I mentioned in post #24, I think you want a schottky diode there. The 1N4007 is certainly a workhorse, but it's not schottky.

Using a 0.1" pitch perfboard and through-hole components, I think I could beat that size, but only by leaving off the screw terminals. But for that price, why bother? The terminals are labelled on the back of the board. Two for power (VCC), two for input (Vin), two for output. It takes a voltage input (like from a potentiometer), and uses that to control the output. The PWM output has a period (time it takes for one cycle, or the inverse of frequency) that is controlled by the on-board pot. The PWM duty cycle (fraction of the period that the output is high) is controlled by the input voltage. So as the input voltage varies from 0-5V (or 0-10V) the output duty cycle varies from 0-100%. 

The LED brighness is controlled by the duty cycle. If you have an AMC7135 driving the LED and you turn it on and off so fast that you can't tell it's flashing, and say it's on 60% of the time (60% duty cycle), it will appear 60% as bright. It's changing the _average_ current, even though the _instantaneous_ current is always either 350 mA or zero. By changing the duty cycle, you change the average current and the apparent brightness.

On the voltage to frequency board, the input voltage is used to control the output frequency, instead of the duty cycle.

After all that though, I don't think that board is what you want, as it needs 5V to power it. It may run okay on a single cell, but I wouldn't bet on it. It's a cheap gamble though.

If you ever want to make your own circuit boards, check out seeedstudio.com. You can get them amazingly cheap. All the boards for the drivers I sell come from there. They aren't fast, but the price is right and the boards are good.


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## degarb (Nov 17, 2016)

DIWdiver said:


> After all that though, I don't think that board is what you want, as it needs 5V to power it. It may run okay on a single cell, but I wouldn't bet on it. It's a cheap gamble though.



Unclear here. Are you saying neither board, or not the second board? The ft pwm board still looks good to me.

Also, what about pwm dc motor controls: 

https://www.amazon.com/gp/product/B00XE965RG/?tag=cpf0b6-20

https://www.amazon.com/dp/B00N30UK2M/?tag=cpf0b6-20

I am guessing, no, because I am missing some unnamed variable on these motor boards.


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## degarb (Nov 17, 2016)

Side notes: for future generations googling this thread, it would a lower pwm frequency has fewer switching losses, higher less noticeable. Correct me if I'm wrong. 

Also, my poor worker's hearing aid was ringing when working with my home made buckpuck 700 headlamp. I am guessing the dimming pwm was creating am noise. Solution was to turn aid volume low. Didn't try shielding with foil.


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## DIWdiver (Nov 17, 2016)

degarb said:


> Unclear here. Are you saying neither board, or not the second board? The ft pwm board still looks good to me.
> 
> Also, what about pwm dc motor controls:
> 
> ...



The voltage to PWM board wants 5-12V to run it, which you don't have. You're close, though, so it might just work. The voltage to frequency board wants 13.5-30V, so that almost certainly would not work on a single cell.

Either of the motor speed control boards should work.


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## degarb (Nov 17, 2016)

Any idea, by looking at the picture, what to short on: https://www.amazon.com/gp/product/B00XE965RG/?tag=cpf0b6-20
? 

On back of board I tried jumper the two pins near 3-15v to make it low voltage, but still no voltage out with 4.2 in. . No manual with it or online. . Seller and community not responding. . Maybe mine is a dud.. . Should get some voltage out.


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## degarb (Nov 17, 2016)

Maybe the resettle fuse is tripped. . Where would that be? . Not ordinary fuse.


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## degarb (Nov 17, 2016)

My best guess http://belfuse.com/circuit-protection/ptc-radial-lead-resettable-fuses/ so, disconnect power resets. . Likely bum board. I think I found right solder short.


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## DIWdiver (Nov 17, 2016)

degarb said:


> My best guess http://belfuse.com/circuit-protection/ptc-radial-lead-resettable-fuses/ so, disconnect power resets. . Likely bum board. I think I found right solder short.



Yup. Probably a cheap knock-off, but same idea. Actually, all you have to do is remove the load (or turn the PWM all the way down) and it should reset. They work by having a low resistance when cool and a pretty sudden and large increase in resistance at a certain temperature. The large current at low resistance heats it up, and the resistance goes way up. So you have a small current in a large resistance, and this keeps it hot (tripped). Once the current is reduced enough that it cools down, that resets it.

Best guess what to short is on the back, two little solder bumps right above where it says "3-15V", which it sounds like you did. Did you turn the pot? If it's turned all the way down you should get nothing at the output.

Quite possible you have a dud. Those super-cheap products don't have a good reputation for quality.


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## degarb (Nov 18, 2016)

Thanks. 

I jumpered the near fuse side, on that board, to the vout bottom right pin of the chip that looks like an amc7135 but has 78109 printed on it. . Only 6ma to a mere 800 ma on fresh 18650 . 300ma max on 3.3 v cell. . Nothing, as expected at 3volt. I have not tested running an AMC yet. . I also wish to compare lux against identical tail cap with a pot resistor. I did find another Amazon module that claims 1.8 volt low. . I am guessing my current board has too much resistance. 


A retired electronic engineer friend gave me a promising breadboard and 555. I snagged SMD 555s from DigiKey which are too small . I also only got one diode. Will need to revisit your 555 spec. . DigiKey broke my 21 dollar order into 2 parts, for a $31 total with tax and shipping. I cannot complain considering competition shipping and my first order. I found one radio shack holdout not to far. But doubt they have the schottky Diode. I also need transistors. Correct ones for the home 555 circuit.


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## degarb (Nov 20, 2016)

Too much to do this weekend. . Next test is to pwm vdd of amc7135, but down to last two. I think I might try voltage injection first up to 6 v. Then use this motor board to pwm chip. Then kill it. Unless, I get better scheme for boost voltage just on vdd via the cell. I reason that the vdd is sensing not the vout. But probably backwards. 

The radio shack was out of switching diodes, and mosfet gate is 2to4v which would only work on fresh cell. . Is any switching diode a schottky? 

Typing from phone on the shoe box with lux meter and xpg 3 taped on either side. . As suspected by common sense, the resistor is brighter at all tail cap currents. This pwm board has enough resistance so it is only slamming led at 800ma and pwm to lower ma, so way better efficiency Tham my 6x amc7135 at 2.4amp.

Pwm board
Ma lux
50 162
100 354
150 516
200 680
250 840
300 995
400 1304
500 1615
600 1780ish current jumped past
700 2150
4.05 volt

Resistor pot
50 186
100 372
150 542
200 753
250 916
300 1085
400 1398
500 1645
600 1928
700 2170


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## DIWdiver (Nov 20, 2016)

Here's a site you might find interesting: http://www.pratikpanda.com/amc7135-pwm-led-control-max-frequency-speed/

There are some great screenshots here, but the conclusions drawn are not so dependable. After the last screenshot, he says this is the lowest duty cycle (DC) possible. That's not even close to true, and neither is it what he meant to say. He should have said that was the lowest on-time possible. But that's a judgement call. He's assuming that nearly linear DC-to-lumens is a requirement right down to the minimum allowed DC.

At the displayed pulse width of 12 uS, you are getting about 2/3 of the output that the DC would suggest you should get. You can tell this because the current pulse is about 2/3 the area of the 'ideal' pulse. The author suggests that operation below this is not possible. But if you reduced the on-time to 8 uS, you would still get usable output.

If you accept that at very low on-times (associated with but not the same as low DC) the lumens will drop faster than the DC, you could go right down to about 4 uS, at which point the output would be pretty near zero, certainly far below what the DC would suggest it should be.

For example, if you wanted to run the PWM frequency at 50 kHz (say, to avoid lines in your video), a 25% DC would give 12.5 uS on-time, and substantially less output than you would expect. However, if you ran at 1 kHz, that same 12.5 uS on-time would be a DC of 1.25%.

He also states that if you run at less than 5 kHz, you run the risk of visible flicker. This is totally bogus. Most humans have a hard time detecting flicker above 100 Hz. Very, very few are sensitive to it at 200 Hz. It's generally believed that at 500 Hz, it's beyond human perception with stationary or slow-moving objects and light sources. It's generally not difficult to run 1% DC at 1 kHz, which would provide a substantial margin for error.

By the way, the schematic he posted is not clear what the capacitor value is. It could be 100 uF or 100 nF. To me, it's quite clear that the intended value is 100 nF (0.1 uF). 100 uF would be just stupid, and could not have produced the screenshots posted.

The good news is that you should be able to do exactly what you want with the '555 circuit driving Vdd of the '7135, no FET. After looking at the data sheet, I believe that the ICM7555 (and many other low voltage '555 chips) should be able to drive Vdd of the '7135 satisfactorily down to a supply voltage of 3.0V, and probably as low as 2.7V.


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## degarb (Nov 21, 2016)

DIWdiver said:


> Here's a site you might find interesting: http://www.pratikpanda.com/amc7135-pwm-led-control-max-frequency-speed/
> 
> There are some great screenshots here, but the conclusions drawn are not so dependable. After the last screenshot, he says this is the lowest duty cycle (DC) possible. That's not even close to true, and neither is it what he meant to say. He should have said that was the lowest on-time possible. But that's a judgement call. He's assuming that nearly linear DC-to-lumens is a requirement right down to the minimum allowed DC.
> 
> ...



Interesting. . 

First glance, two questions. . My next order, DigiKey icm7555, larger 7.6mm with be sized pins? I want to use radio shack breadboard pic 1 276-159 as I recall. . Second, as others, I want to minimize space and weight, his drawing cap protects the led out pin : with pwm, would this be more important, even if l2 was shorter than 3 cm? https://drive.google.com/file/d/0ByvnKHNhvrTmcEM0dTJXQ0hLcFk/view?usp=drivesdk


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## DIWdiver (Nov 21, 2016)

That Radio Shack number comes up as a heatsink. But most of RS's breadboards are 0.1" pitch, which fits nearly all DIP packages, including the ICM7555IP, which would be my pick from DK.

Using PWM on Vdd should have no impact on the requirement for the output capacitor.


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## degarb (Nov 22, 2016)

Hello. . Should report, I wired up another amc7135 minus the caps. . (Brightness, I suppose, was a hair at or slightly above the pot at same current, which is good.). I rewired my 555 SMD tangle to the vdd. I was very happy to see cc dimming without killing the amc7135 over about a half hour of tests. 

Unfortunately, for some reason, the smd 555 I chose(pwm the vdd) , is only allowing the amc7135 to do 6 to 170 ma (with xpl hi, very useful runtimes, but not quite good enough for ideal 2 to 3 meter detail inspection) . Maybe resistance on untrimmed wire of 22 Guage, or my choice of 555. Well, another DigiKey order, and mockup on board, should get a higher current. . If not, then the schematic fault, which I doubt. . Then the work around would be to use this to drive 2 amcs or mosfet.

Just a quick check of my DigiKey cart looks like the dmg mosfet I chose isn't sip 1, smdish looking. On phone, anyway couldn't find any with breadboard style fins, using Google or their internal search. . Maybe will have better luck this evening on desktop, if I have a chance. And figure out a better search string...


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## degarb (Nov 22, 2016)

Still trying to cheat. Actually, trying to figure out all avenues-cost, time, form factor. 

So, I got this: http://m.tomtop.com/modules-219/p-e1002.html
Tomtop looks same for half the price of Amazon prime. Not bad, as the Amazon one has switch, very smooth current control from 6ma to full power. . Maybe the screw down terminals could be popped off to save some space. Maybe corners of board trimmed. I imagine a little heat gun heat, and she should roll up nicely like a fruit roll up and stuffed in the tail cap. Right? 

Joking aside, Seems to fall out of regulation about 3.1 to 3.2 volts using this board. Something like 200 ma at 3.1v . Though have yet to test the amc7135 regulation to verify spec sheet... As with the other board, lower lux number compared to the variable resistor. Though certainly, a percent drop or 3, due to board losses. These have no periodic control. 

With a 2.74v cell, I was surprised to see 20 ma and dimly lit led. 

Hooked board positive out to the vdd, and grnd pin to board motor negative. Probably, should try vdd straight to batt. But, then the chip might have slightly higher vdd voltage and sink less current? But maybe lower dropout voltage?


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## degarb (Nov 23, 2016)

Knocked together, this evening, my friend's 555 chip, taking my only schottky off other 555 circuit, on the pic 1 279-591b board from radio shack. I was concerned my dmm could not get a forward bias read on the schottky, and who knows how old the 555 was. . Didn't work this time. . Just put out 250 ma and no dimming. I promptly unhooked,as to not damage my AMC. 

So, in this circuit what would be a symptom of a bad diode? 

Any tips for breadboard? . It was reeeealy hard not to over flow solder onto next aisle, if you will. . Even tried cheating with lead solder paste. I did check to make sure no conductance between rows.


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## degarb (Nov 24, 2016)

https://www.radioshack.com/collecti...neral-purpose-ic-pc-board?variant=20332061061

In addition to my schottky possibly bad question. . (may have touched 2 live wires in prototype), two breadboard questions. 

What is best tool for trimming it? . It seems like it may shatter if I use tin snips. . I am thinking dremmel but have had 3 die after a few DVD buffing in last 3 years, so probably need to pony up another $30.

And I think I should have used thinner solder wire. Got some, but doubt it has built in Flux. Only Flux I have came with my silver solder and butane torch, which may be a different formula.


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## DIWdiver (Nov 24, 2016)

You can probably just snap it. If you're shy, then score it heavily on both sides with a utility knife first. I do that all the time with perfboard (just an array of holes on 0.1" centers). Otherwise saw it.

Silver solder flux may not activate at soldering temperatures, or it might work fine.


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## degarb (Nov 24, 2016)

You any idea what a bad schottky will do in this circuit? 

Yep, I used .062 solder. Sparkfun recommends. 02 but think they have a steep shipping. . DigiKey has. 02 lead half pound for 20. Lead might not need Flux. . Little more than I intended, but other than health, I am guessing it would be as good in all adhesive respects as lead free.


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## degarb (Nov 24, 2016)

You know..... It just occurred to me, near my tail cap, I could wrap the 555 circuit around on the exterior of light. This should be smallest configuration. . I use plenty of amazing goop and Bob Smith 6 minute epoxy. I built one convoy replacement test light. . Started with coke can wrapped around 18650 epoxied into a tube. Used...zebra style. Hlamp. 80 G. 
Haven't ordered. Cccv on board usb charger, size unknown.


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## DIWdiver (Nov 24, 2016)

A bad diode would screw up the timing. But it's very unlikely it's bad. They are pretty rugged and you aren't doing anything harsh to them. You should be able to test it with a DMM.

Tin/lead solder is in most respects superior to lead-free. And unless you significantly overheat it, there's very little health risk to using it. The reason it is banned in many locations is that electronic waste leaches lead into the environment, not because lead solder is dangerous to either the assemblers or users of electronic products.


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## degarb (Nov 27, 2016)

DIWdiver said:


> A bad diode would screw up the timing. But it's very unlikely it's bad. They are pretty rugged and you aren't doing anything harsh to them. You should be able to test it with a DMM.
> 
> Tin/lead solder is in most respects superior to lead-free. And unless you significantly overheat it, there's very little health risk to using it. The reason it is banned in many locations is that electronic waste leaches lead into the environment, not because lead solder is dangerous to either the assemblers or users of electronic products.





When I made my first 555 wire build, I could dmm see the forward bias. . Being my only diode, I used it on my bread build. . Now, no fw bias for nothing. . Either being an SMD schottky, I killed during first solder, which is why I could only get 1 to 50 AMC output, or dmm diode test is bad while ohm works, or I killed it mechanically. 

My bb turned out 3x3 cm. . I could beat the pwm boards with bb if I could get a flexible version that could bend. I would move the pot to other end of light. . The wiring would be easier with bb, but I think needs to be thin and flexible.


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## degarb (Nov 27, 2016)

https://www.amazon.com/dp/B00Z244HNU/?tag=cpf0b6-20

Will the above work? 

Having only 2 builds to my name, one in the 80s, I have no idea if the above would be useful. I suspect we need to make our own connections between holes. And not seeing hole separation width. Pic 1 means 1 mm? Sorry, forgetting.

I actually see three 555s at Radio Shack, the one that remains in my county. Though they are 6 times the price of digikey. No schottky. Anyway, my issue is splitting off in different directions on pin 6,7, 1 and 8. I don't see a simple way of forking with wire. While a tiny bit of flexible pcb seems an elegant enough solution...Though I suppose, there probably is an even better approach the junctions that would obviate the pcb.


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## degarb (Nov 27, 2016)

https://www.amazon.com/dp/B005T8Y20W/?tag=cpf0b6-20

and

https://www.amazon.com/dp/B00K2FTE28/?tag=cpf0b6-20

Now, I am seeing people on youtube drawing their circuit with a marker then etching the copper. Apparently, the acid is not able to get through the marker? Or is it a special marker?

Now, the 555 is just few connections between pins and a diode between pin 7 and 6. This part could flex around tail cap. On the head side, I would put the pot, 2 resistors and cap. This would be very light and small-elegant enough. I would just 5 minute epoxy on outside of tube; epoxy to water proof.


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## degarb (Nov 27, 2016)

diw, one probably silly question. One more, that is. on this schematic https://cdn.instructables.com/FGN/8X56/GBF5KOQQ/FGN8X56GBF5KOQQ.MEDIUM.gif
what does the cw mean? 

My read is pin 7 is in swiper 2 on pot, vs is pot pin 1 and pin3 of pot. I may have connected both vs and pin 7 on swiper the first wired time. Possibly my half current cause?

I think pin 5 is not to be connected, according to another builder. Though, it looks to me like it could come in right before cap.


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## degarb (Nov 27, 2016)

Lord, I am a pain. Anyway, done with research for the day and off to other unrelated pursuits. 

But, I just found https://www.fasttech.com/products/0...m-ss14-chip-1n5819-schottky-barrier-diodes-50 these are barrier schottky diodes. The word barrier is new. A quick google is not pulling up any difference from a schottky. I need a few other things from fasttech, anyway..


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## DIWdiver (Nov 27, 2016)

CW means clockwise. That's the end that the wiper moves to when you turn the knob clockwise.

The flexible perfboard doesn't look flexible enough to be useful for your needs. Yes, you'd have to provide connections between holes.

Pin 5 does not need to be connected. In some cases a capacitor to ground is used to make the timing more stable. You don't care if it varies a tiny bit from cycle to cycle, so you don't need it.

Those diodes will work. Not sure they'll work as well as the ones I suggested, but they will work.

Be careful of Radio Shack 555s, as they are probably not low voltage ones.


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## degarb (Nov 27, 2016)

Thanks for all the answers. Certainly more than you signed up for. 

Still curious if you think, my wiring vs through r1 into 2, along with 7, caused my current to limit at 170 ma, pwm on the vdd. Or something else.

Have you ever etched a copper circuit, with pen. Looks too useful to ignore. I just haven't yet enough time to locate an instruction page or talking youtube video, explaining the process. Bread boards are fine protyping, but seem limited unless it can flex for form factor reasons.


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## DIWdiver (Nov 28, 2016)

degarb said:


> wiring vs through r1 into 2, along with 7,



I have no idea what that means.


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## degarb (Nov 28, 2016)

DIWdiver said:


> I have no idea what that means.



In first build, using his hand drawn detailed schematic, I wired incoming positive and pin 7 of the 555 into pin 2, the swiper of the pot. . Wondering is reason I got only 170 ma max out of the amc7135 to the led. Pwm on vdd of AMC.


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## DIWdiver (Nov 29, 2016)

Connecting pin 7 to the supply voltage would be very bad. I wouldn't want to guess what would happen, as you would be trying to crowbar the power supply.

To 'crowbar' a supply means to throw a crowbar across the terminals. Pin 7 has a transistor to ground. When it gets turned on, it would be right across the supply. It would be a good way to damage something.


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