1D lights?

[xxo]

Just to verify, is this the one?

https://www.walmart.com/ip/Eveready-Economy-LED-Flashlight/50033830?

Gotta check these things before laying down the princely sum of $2.47. Seriously, thanks for the pointer and discussion. I can see lots of uses for a long-lasting, modest output light like this.

The Photo looks like the right one (25 lumens/60 hr. run), but the description says 125 hrs (probably an old spec for a lower lumen version).

They sell these things all over including Home Depot and even some grocery stores. I noticed my local Walmart was recently closing these out for $2 (along with Mag Solitaire LEDs for $7).

 

[dgbrookman]

Just to be clear, I am running these with a 39-ohm resistor in-line between the cell and the circuit. (Nothing fancy, just taped to the top of the cell with some electrical tape for insulation). That is why I got 800+ hours from it--without the throttle, I would have gotten more like the manufacturer's 60 hours.

Thanks for the clarification. Any idea how much power is dissipated across the resistor? To my limited understanding of these things, the LED doesn't appear as a simple resistive load so a straightforward Ohm's Law calculation wouldn't work. I'm asking because it could be useful to specify different resistor values to trade brightness for run time.

 

[lampeDépêche]

Thanks for the clarification. Any idea how much power is dissipated across the resistor? To my limited understanding of these things, the LED doesn't appear as a simple resistive load so a straightforward Ohm's Law calculation wouldn't work. I'm asking because it could be useful to specify different resistor values to trade brightness for run time.

"To my limited understanding"? Those are fighting words, pal--MY understanding is FAR more limited than yours. Hell, my lack of understanding will meet your lack of understanding behind the gym after school, and settle this once and for all.

More seriously, I just don't know enough to know how I would calculate the power-loss, whether or not the LED is a simple resistive load. Lynx Arc did some quick calculations that suggested that the resistor might be burning up maybe 5% of the power, but I don't know what assumptions lay behind those calculations.

For what it's worth, the 39-ohm resistor is just the standard Radio Shack, 1/4 watt axial lead, about 6mm long and 1mm in diameter.

Also--the light-engine itself imposes some limits on how much resistance you can introduce. On the Eveready 1-Ds, the light would not start up with more resistance than 39 ohms, even on a fresh cell. A different light-engine will be able to start up with less current. I tried this trick with a Klarus Mi02, and it would light up with 150 ohms of resistance, though it was unusably dim. The Eveready did not light up at all, even with a 56-ohm.

I am in the middle of a longer-run experiment with a Gerber Infinity Ultra, modded with a Yuji 5700k, with an 82-ohm resistor on the back end of the battery. It puts out an even 0.3 lumens, my ideal for a night-time walk-around light, and it has been doing it for exactly two weeks today. That's over 330 hours on a single Eneloop AA. Of course, the ZL AA lights claim to put out that much light for 3 weeks, so I'll have to see how it goes for the next week.

In any case--for a given light engine, you will have different options for how much resistance you can introduce. I wish I knew enough to know how to calculate stuff!

 

[Lynx_Arc]

. I wish I knew enough to know how to calculate stuff!

Just use Ohm's law there are calculators online for it you can plug in the resistor and measure the current in the circuit and calculate the voltage E=IR where E is Volts, I is Amps, and R is Resistance. You can then measure the total voltage across the circuit and use Watts Law which is P+IE where P is power in Watts, I is Amps, and E is volts. Once you know the total watts you can subtract the watts used by the resistor and divide it by the total to get the ratio of power used by the resistor to total power.

 

[dgbrookman]

"To my limited understanding"? Those are fighting words, pal--MY understanding is FAR more limited than yours. Hell, my lack of understanding will meet your lack of understanding behind the gym after school, and settle this once and for all.

Humpf. If it's true that "a little knowledge is a dangerous thing" then I am Han Solo, the Incredible Hulk, and James Bond all rolled into one.

As Lynx Arc says just above it should be possible to work it out with Ohm's Law (which is pretty much all I know about electronics). Assuming you have a multimeter the steps would go something like this.

With the circuit operating, measure the voltage across the resistor. Call this Vr (r for resistor).

By Ohm's Law the current flowing through the resistor is then equal to Vr / R, where R is the value of the resistor, i.e. R = 39 ohms in your case. Call this I.

Since it is a series circuit then the current flowing through each of the components is the same for every component, namely the value I you just computed. I think this is right even though the LED is not an ideal resistive load.

Now measure the voltage across the + and - ends of the battery. Call this Vb (b for battery).

The total power through the circuit is Vb times I. Call this Pt (t for total).

The power dissipated by the resistor is Vr times I. Call this Pr.

The fraction of the total power "wasted" by the resistor is equal to the ratio of the power dissipated by the resistor to the total power of the circuit, that is, Pr divided by Pt.

Lynx Arc knows a lot more about this stuff so he can correct anywhere I've gone wrong.

 

[Lynx_Arc]

Humpf. If it's true that "a little knowledge is a dangerous thing" then I am Han Solo, the Incredible Hulk, and James Bond all rolled into one.

As Lynx Arc says just above it should be possible to work it out with Ohm's Law (which is pretty much all I know about electronics). Assuming you have a multimeter the steps would go something like this.

With the circuit operating, measure the voltage across the resistor. Call this Vr (r for resistor).

By Ohm's Law the current flowing through the resistor is then equal to Vr / R, where R is the value of the resistor, i.e. R = 39 ohms in your case. Call this I.

Since it is a series circuit then the current flowing through each of the components is the same for every component, namely the value I you just computed. I think this is right even though the LED is not an ideal resistive load.

Now measure the voltage across the + and - ends of the battery. Call this Vb (b for battery).

The total power through the circuit is Vb times I. Call this Pt (t for total).

The power dissipated by the resistor is Vr times I. Call this Pr.

The fraction of the total power "wasted" by the resistor is equal to the ratio of the power dissipated by the resistor to the total power of the circuit, that is, Pr divided by Pt.

Lynx Arc knows a lot more about this stuff so he can correct anywhere I've gone wrong.

You got it right..... and those who are confused with the V vs E.... V=Volts E=Electromotive force (also volts)

 

[flatline]

Both Targets I've been to this last week still have a space for the Eveready 1D, but are completely sold out. The Walmart had them on clearance for $3 for a 2-pack.

I hope this isn't an indication that they're being discontinued...unless they're being replaced by something even better...

--flatline

 

[lampeDépêche]

I hope this isn't an indication that they're being discontinued...--flatline

No, it's an indication of the incredible influence that Candelpowerforums has. All around the country, people have been talking to their neighbors over the back fence, saying, "did you see that post by flatline on 1-D lights? We've got to get down to Target right now!"

It's practically a stampede. It's Tickle-Me Elmo all over again, except for flashlights.

 

[scout24]

They're on sale at my local WalMart, too.

 

[flatline]

Well, let's hope that whatever replaces them is at least as good.

It's tempting to pick up a couple more 2-packs, but, really, I have enough. I bet once they disappear from Walmart and Target, they'll still be available for a while from Big Lots and Bargain Hunt. It takes a while for those places to go through inventory.

--flatline

 

[lampeDépêche]

Last night, my Eveready 1-D running the used Duracell was still putting out usable light. Tonight it's dead.

That's 45 days and nights, continuously on, 1080 hours, from a battery that was rated at 60% by the ZTS meter before I started.

When I pulled the battery out, the voltage read 0.176v.

Ten minutes later, it has recovered back up to 0.206v. I think that is pretty definitively drained.

I'm putting in a fresh Duracell. ZTS 100%. 1.61v on the DMM. I'll get back to you in a few months.

 

[dgbrookman]

Finally got around to picking up a couple of these and did some testing. I don't have a 1D battery holder handy so I just rigged up something by taping test leads onto the supplied heavy-duty cell. Here are results for various resistor values.

R	Vb	Vr	Vf	I	eff	hours	days
10	1.61	0.69	0.92	66	57%	121	5
22	1.62	0.78	0.84	35	52%	229	10
33	1.62	0.81	0.81	24	50%	330	14
47	1.62	0.83	0.79	18	49%	452	19
100	1.63	0.96	0.66	10	41%	824	34

R is the nominal value of the resistor
Vb is measured voltage across the +/- ends of the battery
Vr is voltage across the resistor
Vf is voltage across the LED
I is current (milliamps) calculated as I = Vb / R
eff is "efficiency" defined as power consumed by the LED divided by total power supplied by the battery
hours is a crude estimate of battery life in hours obtained by dividing the rated battery capacity by I, and days is the equivalent number of days.

Subjectively the brightness with the 10 ohm resistor is a little lower than with no resistor. The 22, 33 and 47 ohm resistors are a little dimmer still but there isn't a huge difference between them. With the 100 ohm resistor the light is quite dim. It's similar to or maybe a little dimmer than the moonlight mode on my Nitecore Tip which is supposed to be 1 lumen.

The efficiency and lifetime values shouldn't be taken literally because things will change as the battery runs down. As the voltage decreases there will be less current drawn (this relation between voltage and current is a basic characteristic of LEDs) so the actual lifetime will probably be longer. This is consistent with what lampeDépêche said about getting 45 days of life when using a 33 (or was it 39?) ohm resistor. Maybe these values are somewhat useful in a relative sense.

My ramshackle "workbench" isn't much to admire and there are lots of smart people who probably knew about this sort of thing already. But it was a fun little experiment and it inspired me to look into some of the principles about how LEDs work.

 

[Lynx_Arc]

You really cannot get a good idea of LED power and efficiency using resistors with having a boost circuit involved in the midst as it can range all over the place in efficiency. Even though a resistor can increase runtime by throttling down the power to the LED in the end it also interferes with the efficiency of the boost circuit. As your chart equates you can greatly increased runtime but loose a lot of power but also to a certain extent the eyes can manage the loss of output for the tradeof in insane runtime.

 

[xxo]

Finally got around to picking up a couple of these and did some testing. I don't have a 1D battery holder handy so I just rigged up something by taping test leads onto the supplied heavy-duty cell. Here are results for various resistor values.

R	Vb	Vr	Vf	I	eff	hours	days
10	1.61	0.69	0.92	66	57%	121	5
22	1.62	0.78	0.84	35	52%	229	10
33	1.62	0.81	0.81	24	50%	330	14
47	1.62	0.83	0.79	18	49%	452	19
100	1.63	0.96	0.66	10	41%	824	34

R is the nominal value of the resistor
Vb is measured voltage across the +/- ends of the battery
Vr is voltage across the resistor
Vf is voltage across the LED
I is current (milliamps) calculated as I = Vb / R
eff is "efficiency" defined as power consumed by the LED divided by total power supplied by the battery
hours is a crude estimate of battery life in hours obtained by dividing the rated battery capacity by I, and days is the equivalent number of days.

Subjectively the brightness with the 10 ohm resistor is a little lower than with no resistor. The 22, 33 and 47 ohm resistors are a little dimmer still but there isn't a huge difference between them. With the 100 ohm resistor the light is quite dim. It's similar to or maybe a little dimmer than the moonlight mode on my Nitecore Tip which is supposed to be 1 lumen.

The efficiency and lifetime values shouldn't be taken literally because things will change as the battery runs down. As the voltage decreases there will be less current drawn (this relation between voltage and current is a basic characteristic of LEDs) so the actual lifetime will probably be longer. This is consistent with what lampeDépêche said about getting 45 days of life when using a 33 (or was it 39?) ohm resistor. Maybe these values are somewhat useful in a relative sense.

My ramshackle "workbench" isn't much to admire and there are lots of smart people who probably knew about this sort of thing already. But it was a fun little experiment and it inspired me to look into some of the principles about how LEDs work.

Thanks for the info. Did you have any data for the stock 1D without a resister?

 

[lumen aeternum]

Change resistor value to maintain constant brightness? Variable resistor?

 

[dgbrookman]

Did you have any data for the stock 1D without a resister?

Without a resistor Vb = Vf, which measured 1.516 V. Since there's no resistor we can't use Ohm's Law to calculate I = V / R. However -- as mentioned there is a more-or-less linear relationship between I and Vf once you get past the low-voltage "knee" in the curve. Eyeballing a linear fit to the measured values of Vf and I, then extending it upwards gives I = 220 mA at Vf = 1.516 V.

Unfortunately I can't figure out how to post the Excel graph.

 

[flatline]

Target stores in my area have all re-stocked the 2-packs.

--flatline

 

[bykfixer]

Finally had a reason to visit my local HD. $5.48 for a twin pack. Bought some #12 silicone o-rings for grip rings then asked myself "now why did I really come here?, oh yeah, paint."

 

[Lynx_Arc]

I was at Walmart the other day and saw something interesting..... a 1D light made by Ozark Mountain I think...... had a "chip" emitter and a magnifying lens and the case looked like the Energizer case with the same click switch. Price was under $3.

 

[xxo]

My 1d eveready started flickering, turns out the problem was the strip of metal that connects the switch to the head of the light was bent and not making good contact - the metal strip is way too thin and easy to bend IMHO. Just a quick heads up in case anyone runs into this issue.