# DC generator



## Clouddancer (Jan 22, 2003)

Can anyone make suggestions where to find small DC generators or DC motors and small clockwork gearing parts? Would like to build my own no battery lamp that would run much longer than Freeplay's with either spring power or capacitors.


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## Hemingray (Jan 23, 2003)

I had sent this in response to an e-mail inquiry, thought I'd also post it here...

I'd look in any electronic surplus or junk shops, check out places like All Electronics, Jameco, Hosfelt, look in any electronic hobby magazines, etc. Hobby and model making shops will have these, but the prices will be higher, Unless they sell surplus. 
A "gearhead" motor is the easiest, as it incorporates the speed "step-up" all in one unit, but you don't want too great a gear ratio, else the effort 
To turn the motor may be too much, or it may not turn at all. Something like 10-20 to 1 (going from output shaft to motor, (they are actually rated as 1:10, 1: 20 reductions). I've played around with this since I was a kid, way 
Long ago, using various Erector Set / Mecanno Set parts and small "toy" DC motors. Another possible source would be smaller motors used for "robotics" Experiments, smaller and less powerful versions of the machinery used in "Robot Wars" and similar shows on cable TV. A permanent magnet DC motor (the most common small and inexpensive type) will generate DC, polarity is dependent on direction of rotation. A "stepper" motor if it has a permanent magnet rotor, will generate multi phase AC, which can me rectified and turned into DC, with no directional polarity differences. Steppers can be found in old 5" floppy drives, old magtape drives, and the like. Small DC Motors can be salvaged from toys, CD and floppy drives, etc. 

I've taken a couple of the cheap made in China (or Russia) "squeeze generator" flashlights - sometimes called "Forever Lights" and converted them to LED, these generate AC, so I added a DIP size full wave bridge rectifier and a "supercap", and changed from incandescent bulb to a home made 3 -LED "bulb" that screws into the original socket. These are always good for an emergency, as no batteries are involved. 

If one is lighting white LEDs, the power needed is about 60 to 80 milliwatts Per LED. So three, would be approximately 200 mW (1/5 watt). Just for comparison, one HP is equivalent to about 750 Watts, more like 1000 watts in the real world, accounting for various inefficiencies. 

--Edward W. Brown


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## Marked (Jan 23, 2003)

http://www.sidewindercharger.com/

http://www.scientificsonline.com/
http://www.scientificsonline.com/ec/Products/Display.cfm?categoryid=192964


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## Clouddancer (Jan 23, 2003)

*Hemingray* and *Marked*, thanks very much. Excellent and very useful. Going to save this page for reference. The Edmund Scientific links show some very interesting possibilities such as running their high torque motor/gearboxes backward. Now to find the long run spring to with it. I ran across at least one Chinese company during a search that makes the coiled constant force type, one of which Freeplay uses.
Hemingray your info will be very helpful in making it practical.

Another question for you guys: It sounds to me like you could use one of these miniature motor & gearboxes to charge up large capcitors and use them to release regulated power. On the other hand using a large coiled spring geared right to slow it down and run a DC motor to a regulator sounds like it would do the same thing. However what's your opinion of which would likely result in the longer run time and which do you think might result in the least amount of cranking versus run time? I'm guessing with spring powered you would still need to use capacitors but geared right the spring might keep them charged up longer than direct hand cranked charging.

No doubt if I can produce the right power you guys can suggest LED arrays that will burn holes in the wall.


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## **DONOTDELETE** (Jan 23, 2003)

here's another, an Alladin foot operated one -- "coming soon" --
http://www.aladdinpower.com/steppage.htm


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## [email protected] (Jan 23, 2003)

CD, the 2020 has more spare room than the Coleman, but because the spring mechanism takes up quite some space, actual "modding" room might be restricted...




There should be ample room for improvements though.


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## Clouddancer (Jan 23, 2003)

So what about the question above, Bart, Hemingray? It sounds like you guys are already familiar with the 2020. Would you suggest modding the 2020 with supercaps for longer run time or would that accomplish anything without a more powerful spring? Any other suggestions for longer run time using only the generator?


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## LoneRebel (Jan 23, 2003)

Clouddancer, it sounds like the energy is stored in the spring meaning that it uses that stored potential energy and converts it at a constant rate into electrical energy in escence the spring *IS* the battery. You could put super caps in but I dont really see much of a point because if you did put the caps in, it would still charge the cap as the spring uncoils. The whole process of releasing the stored potential energy takes place in about 8 minutes(8 mins runtime). The light also has a NiMh battery in it which sounds as if its separate from the crank. This powers a more powerful xenon bulb. What I think would make a nice mod would be to replace that with a nice luxeon side emitter. I'm not sure what the battery configuration is on that light as the specs dont come up but I'd imagine that it is at least 2 NiMh's. A orange luxeon side emitter is still relatively bright at that voltage with 2 NiMh's.

Anyways, that is my take on the subject. Hope it helps


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## Clouddancer (Jan 23, 2003)

LoneRebel -so using the batteries a luxeon side emitter would give more light than the xneon? Why orange?

I was thinking of supercaps to store power because I might be able to find a suitable more powerful constant force spring replacement. I'm new to this but from what I've been seeing on the forum I'm guessing that's the way to extend the run time with just the spring because the 2020's spring already powers LEDs. No doubt with some help I can improve on the LEDs but first I want to improve run time. What do you think?


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## LoneRebel (Jan 23, 2003)

Cloud, since the xenon is an incandescent I'd imagine that it would draw significantly more current than a luxeon thus increasing the runtime plus they never burn out. The amber/orange luxeon star side emitter is one of the few luxeons that does well at low voltages. If the light uses 3 or more cells, then use any color of luxeon. 

Replacing the spring sounds like a good idea, but I'd imagine that they probably put in the largest spring for the available space in the light(just a guess).


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## [email protected] (Jan 23, 2003)

CD, I don't have the 2020, I'm judging from the pic...










A MicroPuck should be able to drive a Luxeon nicely.





I'm not sure about modding the generator itself, maybe replace the NiCd cells with cells that don't have a memory effect?

Since it is no problem to rewind the generator while in use, I'm not too sure what replacing the spring would accomplish, other than a few more minutes light on one wind...


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## PsycoBob[Q2] (Jan 23, 2003)

NiCd's DON'T have a memory effect. They DO have 'Voltage Depression Induced by Overcharging' effect.





NiMH might be better, just for energy-density concerns. Or you could use a 3.6v Li-ion meant for electric plane models. Built-in protection circuitry, light weight, and decent cost... plus bragging rights. Micropuck and Li-ion would work, apparently.

I might make one of these spring-powered lights my next flashlight purchase, if I can find one that can be modded to charge 2AA's for use in other stuff. I saw one locally that had a 12v output at 300mA, for running cell-hone chargers and some low-current battery-chargers.


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## Tomas (Jan 24, 2003)

Right on, PsycoBob!

Memory Effect






==x==


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## Clouddancer (Jan 24, 2003)

Just ordered a Freeplay 2020 (spring powered/LED/rechargeable) from Cheap Sales Mall Freeplay 2020 for only $45. Looks like it has more room in the body for modifications and easier to carry than the Coleman. When it comes in I'll get you guys to help me tweak it. Ha, light saber here we come! The mothership will be pleased.


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## [email protected] (Jan 24, 2003)

I stand corrected!




Tomas: Thanks for the interesting link .




Bob: Is this something simular?




Motorola Freecharge 



btw, someone mentioned (in another thread) that replacing the 2020 with the Sherpa was a step backwards, but, the KISS principle offers greater reliability, and since Trevor Bayliss' first goal was to provide cheap and reliable tools, this is just an evolutionary step.


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## Clouddancer (Jan 24, 2003)

Thanks guys, that is all *very* helpful. I agree Tomas, very informative link. And thanks for the Micropuck link Bart. 

I think you're right about replacing the spring. I've been looking at constant force spring designs in manufacturer catalogs. The two large black discs you see through the case, one with the crank handle, apparently house the two ends of the spring, relaxed or wound. So there's no room to enlarge it and my guess is that the only improvement you could make is with a more powerful spring but the same size. From the looks of the manufacturer's products evidently possible but maybe not worth the trouble. My guess is that it doesn't take eight minutes to unwind put charges a capacitor that will take that long to discharge to the LED draw. If so then perhaps the only pratical improvement might be better LED's but not run time for the spring power. 

Now I'm wondering if you abandoned the spring entirely and used manual crank of the generator directly through a regulator to charge supercaps whether you might have a viable path to improved no battery run time? Maybe power 5W Luxeons that way? No doubt there's a good reason why Freeplay didn't do this. Anyone have a guess?

Improving on the xenon bulb setup with a Micropuck (or Bad Boy from the sound of it on the Manf Ann-Micropuck discussion -interesting) and a side emitter sounds very good. 
Where do you find Luxeon side emitters and 
Li-ions? Li-ions at model airplane shops? Why bragging rights on Li-ions? Just more sophisticated or lighter than Ni-MHs? I take it they don't store as much enegry ("energy-density"?) as Ni-MHs right?


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## LoneRebel (Jan 25, 2003)

Cloud, Supercaps are expensive and are nowhere near the capacity of regular rechargable batteries. The reason why the capacitors work in powering an LED is that regular LED's(non luxeons) need very little power. A single LED will work at around 3.6v @ 20 milliamps. And of course LED's get more efficient as the voltage drops. A luxeon 5W LED is [email protected] milliamps. You'd have one huge and extremely expensive flashlight if you used supercaps to power a 5W for any length of time.


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## Clouddancer (Jan 25, 2003)

Ah-ha, I see. Thanks Lonerebel. Oh well, I guess I'm still ahead with a Freeplay instead of a shakelight because it also carries batteries that it can charge itself. I wonder which puts out more light?


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## Clouddancer (Jan 28, 2003)

Got my Freeplay 2020 today. Well, hmm. It has three white LEDs running directly from the spring powered generator, as best I can tell without a capacitor. The light output from them is pretty wimpy and they are soldered in so they can't easily be changed. The light is actually pale blue not white. But they would be better than nothing as a last resort in a long power outage. Through the clear case it's kind of cool watching how the mechanics work. The reflector surface is nibbed rather than smooth evidently meant to scatter the light for some reason. The light output from the single xenon bulb running off the NiMH pack is pretty good but 45 minutes run time sounds like a lot less than I recall most modders are getting with evidently equivalent light output. The xenon is replaceable so I'm wondering if there's an LED that would put out equal light with slower power consumption. Any suggestions?The NiMHs charge on 6 volts so it can't be rigged to charge from an automobile. All things considered though I guess it's not a bad little rechargeable for the price. I also got to try a shakelight today in Brookstone's. Quite impressive actually, for a single LED. It actually appeared to have better output than the three in the Freeplay by using a good reflector and a magnifying focusing lens that works very well. Hmm.


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## LoneRebel (Jan 28, 2003)

Clouddancer, in the case of you wanting to charge your freeplay 2020 with a car adapter it is usually not much of a problem. Voltage regulators can drop the voltage and dissipate the excess power as heat or you can use resistors. Anyways what you need is something like this www.cetsolar.com/caradapter.htm . I did a search for '6v car adapter' on google and that is the first site that came up. 

Sorry to hear that the LED's arent that bright. I'd be interested to know how much voltage and current are going to those guys. Anyways, a thread was started about the coleman sentinel flashlight which is a freeplay crank driven flashlight. It has a bulb in it that operates in one of two modes 140ma or something like 1.2 amps. 30 seconds of cranking supposedly makes the light shine for around 8 mins. 140 ma is enough to run 7 super bright LED's. It doesnt use a spring and stores its energy in 3 AA 1000mah NiMh's. Anyways, I broke down and ordered one. Its not clear like your freeplay 2020 but it sounds like it'll be a modders dream


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## Clouddancer (Jan 28, 2003)

Cool beans, LoneRebel. Just what I needed. That site also has some interesting lighting products too by the way. I didn't buy the Coleman because it apparently doesn't have an option to charge and store power for a longer run. But I think you're right, the Coleman is probably ripe for modding. I would be very interested in what you find and come up with. I would be willing to sacrifice some run time from the spring power to get brighter output from the LED's. I guess I would have to take it to an electronics repair shop to find out what the generator's output to them is. Since it doesn't use one in that circuit I wonder if adding a capcitor would do that? Have any suggestions for upgrading the xenon? 

Been trying to figure the best way to hook a generator up to a hamster cage...


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## Clouddancer (Jan 29, 2003)

Also -Aha! By removing the spring from the Freeplay a much larger generator could be used turning it into a large dynamo like the Coleman approach. Couldn't that then be used to power up supercaps with regulators for each of the three LEDs or one for all? Maybe even wind up with a longer run time than the Coleman. There's plenty of room for them in the case already. Heh-heh-heh... maybe I could wind up being able to yell "It's alive, it's alive!" 

Update on R&D of the hamster cage dynamo -getting much better performance by using a male and female and spiking the males food with powdered Viagra -bioengineering at it's finest!


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## Clouddancer (Jan 29, 2003)

*Quickbeam* , *LoneRebel* , Oops, I stand corrected! Should have looked into the specs on the Sentinel. Looks like you get about the same run time from the Sentinel as the Freeplay with the same amount of cranking. But now the Sentinel looks much better because it doesn't need the heavy spring and offers a longer run time depending how long it's cranked. I doubt I would want to sit there cranking for 40 minutes at a spell to get a full charge, but the point is well taken. What do you guys think of the concept of using capacitors with a big generator instead of charging batteries? From the pictures it looks like the Freeplay has a much larger generator and there's lot's of room in the case. *[email protected]* , *Hemingray* , where are you?


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## [email protected] (Jan 29, 2003)

CD, 
you must really like capacitors...





As previously posted by LoneRebel, in order to achieve sufficient runtime, it would be very heavy and expensive....





The size of the generator is not nescessarily an indication of it's capacity.


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## Quickbeam (Jan 30, 2003)

"I didn't buy the Coleman because it apparently doesn't have an option to charge and store power for a longer run. "

Actually it will fully charge the 3 AA NiMH's in 40 minutes of cranking, giving about 5 hours runtime at 140 mA. Any amount of cranking puts the power directly into the batteries - no springs, no caps. The bulb then draws the power off from the batteries.


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## LoneRebel (Jan 30, 2003)

Clouddancer, you must be mistaken. The coleman sentinel can be either plugged into the wall in order to be recharged or you can crank the puppy for 40 minutes and obtain a full charge. The 2020 that you are using if I'm not mistaken is the one that has problems charging. The crank if I recall correctly is independant of the batteries in the light meaning that your spring is the battery. As it decompresses the spring, the spring turns a wheel with magnets on it which in turn induces an electrical current in some coils which then power the LED's. Once the spring has decompressed your spring battery is essentially drained. 

The coleman dropped the spring approach and instead opted to go with the battery route. As you crank it, it spins a wheel at high speed with magnets on it which induces a electric current into some coils which is then used to charge NiMh batteries. And from what James S has said, the electricity generating powers of the crank is pretty impressive. Impressive enough that it might be feasable to mount a luxeon star in the light or 7 LED's. I cant wait


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## Icebreak (Jan 30, 2003)

[email protected] -

You know I'm way out of my league here but could it be that the .5-.10 Farad Supercaps pale in comparison to the Super Duper Caps?

Could it be that CD really needs the Super-Duper caps with capacities of 500 F - 2000 F I've heard tell about? Certainly, these are expensive @ $50.00 to $100.00 a piece. Surely thier power density is greater than a NiMH. Thier strength is that they can be charged 1 million times as opposed to 500 - 1000 times for the NiMHs.


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## Nerd (Jan 30, 2003)

I think I remember someone saying that 1 farad capacitor would power a ARC AAA for 3 mins before going into moon mode. Let's take it from here.

1 farad @ 2.5 volts = 60-100 ma current draw for 3 mins

IF 500 farads @ 2.5 volts = 60-100 ma current draw for 1500 mins OR 250 farads @ 5 volts = 120 - 240 ma current draw for 750 mins OR 178 farads @ 7 volts = 0.5 amps - 1 amps for 180 mins. = 3 watts/hr capacity. IF we take 1 2100 mah AA battery, 1.2 volts x 2.1 Ah, 2.52 watt/hr capacity. Even a AA battery is better than the 500 farad capacitor. Needless to say the size of the 500 farad @ 2.5v capacitor would be at least the size of 8 AAs in a 2D series configuration size. I don't see the number of times in which it can be recharged as an advantage unless you are pumping 5 plus amps into it when charging which is cranking.. and that's not going to help extend the burn time of the light a lot.

Forgot to mention that I was thinking of using a 5 watt LS here...


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## Icebreak (Jan 30, 2003)

They are that big? Well that goes to show why I don't say much in Mod Land. It's a shame I don't know anyone that could get a pic of one.


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## [email protected] (Jan 30, 2003)

Hehe, I'm not too sure about that Icebreak...




I'm just a nutcase



with a curious mind...

I'm only trying to interpret the data I've been able to find, but IMHO, putting in expensive supercaps seems like overkill to me.




The ability to be recharged almost indefinitely is nice, but replacing a couple of cheap cells every once and a while isn't such a big deal to me. Another advantage of capacitors is the ability to deliver high currents, but since rechargables have ample capacity to drive a suitable lightsource, this isn't relevant here either.
The 2020 isn't exactly in the "ultra compact, lightweight category"






, the possible weight-advantage of supercaps over NiMh's or NiCd's, is a negligible one to me, but YMMV...

edit: 
Thanks Nerd, you've just cleared up the size thing for me.


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## Hemingray (Jan 30, 2003)

I have the older incandescent Freeplay wind-up flashlight, was considering modding it a while ago, as I figure the replacement bulbs would get expensive. It uses 2 AA size NiCDs 600 to 800 mA/H. Can be chaeged by winding or by using an included wall wart. One could also use a solar panel to charge it up.

Unlike the Freeplay AM/FM radio, which lasts about 30 minutes on a full 60 turn winding, this one only goes for a few minutes. I haven't yet taken it apart to see how much internal space is available for mods, additions, etc, I have visions of that spring "exploding" out of the unit, and creating a tangled mess that even Houdini couldn't undo ;-) 

There is one possibly useful gearhead motor in the latest Jameco Catalog, it has a 19.5:1 gear
ratio, rated at 24 VDC operation. Should work as a generator, but I don't have one (yet) to try out. YMMV (your mileage may vary)

/ed B in NH.


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## James S (Jan 30, 2003)

RE: size of super caps. The 2.5v 1F caps available for cheap at allelectronics.com are not large at all. About half an inch long and a quater inch in diameter. As I mentioned in another post I wired 4 of them together to get 2F at 5v and charged from a squeeze type flashlight (not as fancy a generator as the baygen stuff, but capable of generating up to 6v of you squeeze really fast) I got about 2 minutes of good bright light and then many hours of slowly diminishing light. If you really ran this through an arc head, that might be the way to go. I did try running a single transister step up from it, and it ran it down very quickly, like in 30 seconds or so, so thats not a very efficient circuit





RE: Springs exploding. I pried apart one of those telephone cable spools once. You know the ones that take up a flat cable from both ends via a spring? I was going to try to replace the plug that had gotten a short in it. Well, the thing EXPLODED the spring steel flying all around. Actually got a very minor cut to my chest through my shirt where it hit me the first time, and a few bruises where it hit me other places, like my chin. My eyes and face were spared, but it was not a good experience. I expect that the construction on these wind up things will be better, but please do be careful. It may be a good idea to wear some goggles if you're taking it apart for the first time just to be sure. Those springs are considerably larger and hold more tension than the little one I took apart!


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## Clouddancer (Jan 30, 2003)

First of all on the exploding spring thing: I've been there, done that. The usual reason that happens is because a lot of devices use cheaper narrow springs that are not constant force type and have to be preloaded with tension to function, which is fine for their purpose and cost. But when you remove it's containing device during disassembly your remove it's capture and yes, if you're not careful it will explode in your face. The Freeplay 2020 uses a wide constant force spring in a standalone reel that appears to be almost fully relaxed in it's original wound position at rest. So in that case I'm not too worried about removing it.

As to size I found an interesting 100F 2.5V ultracapicitor with measurements that would allow plenty of room for two in my Freeplay after removing the spring and only the at rest storage reel. I wish you guys would take a look and tell me what you think. In the spec. sheet they compare storage density as superior to batteries and mention one use as "extended power" backup. Maxwell mentions this particular one as being ideal for all sorts of small consumer products. Two in series would allow me to charge and discharge at 5 volts right? I don't know much about electronics so I don't know what that means in terms of Amps and needed cranking to charge it but does that mean with a regulator or something I could trickle discharge it through LEDs? I have a call in to Maxwell tech support to find out and get a price. Please take a look and tell me what you think. Look for the PC100E under "large capacitors" at: Maxwell Ultracapacitors $100 for three + shipping, roughly the size of a zippo lighter.

Here's a quote from an e-mail by another member who seems to know a lot about these and advocates their use.

"As you may know, there is a formula for calculating the total amount of power in a Farad, but I can't recall the formula at the moment. You can probably find it by searching for it on the net. That would tell you exactly how much runtime you could expect out of one of these SuperCaps. You would convert Farads to Watts and 1 Watt is equal to 1Amp X 1 Volt. 
You are correct in that you can charge a SuperCap much faster and more efficiently than you can a rechargeable battery. A SuperCap can also provide power much more quickly than a battery. The difference between a SuperCap and a normal capacitor is that a normal capacitor wants to unleash all of it's power all at once but a Super Capacitor releases it's energy a little more slowly, more like a battery would." 

"They really are a terrific technology that most every day people have never even heard of. I believe in like 10 years that all power tools will use these because just imagine having a cordless drill that can be charged in under a minute! Who really cares that the tool can not hold as much of a total charge as with batteries when you can fully recharge the thing in under a minute? I think they will change the world someday. I hope this info helps. There are those on the forum that know more about this than me." 

If I can get the power storage right I have no doubt you guys can help me make this work.


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## LoneRebel (Jan 30, 2003)

James S, when you put those super capacitors together in series I believe you doubled the voltage but decreased the capacitance by half. 
That is unless super capacitors work differently than normal capacitors. I'd love to be proven wrong in this case though. BTW those powerstor aerogel capacitors say they only have a lifespan of around 1000 hours in the technical specs.


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## James S (Jan 30, 2003)

LoneRebel, I looked up the math for capacitors in series and parallel. When you connect capacitors of differing values in series the value of the resulting string comes out to just less than the smallest capacitor. Here is the example:






So .008uf is a little less than .01uf which is the value of the smallest cap. Pluggin 1F into that is easy enough and it does indeed look like it comes out the 1/2F. Which means what I really ended up with was 1F at 5v. Perhaps it would better hold the power with all 4 of them in parallel. I'll have to try that.

The 1000 hour rating is a bit disturbing as that would limit what you could do with them. Is that charged? Charging? Discharging? I wonder how they measure that. Do they count 1000 hours till they self destruct? Or 1000 hours until they loose half their storage power?

Do other aerogel caps have similar breakdown times? The 100F caps would be very usable for a flashlight. I'll be checking those out too, little bit expensive though.


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## LoneRebel (Jan 30, 2003)

James, it looks like according to the spec sheet that after a thousand hours the capacitance drops by 30% if I recall correctly. So most likely not all that big of a deal. But for building a rock solid emergency device it sounds like it might not be the way to go.

Did you see that there were 2.5v 10 farad aerogel caps for like 3.45 at alliedelec.com? Looks like they are sold out at the moment. Kinda sux there is a $25 minimum order otherwise a $10 handling charge is added.

Clouddancer, let us know how much those maxwell caps turn out to be.


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## Clouddancer (Jan 30, 2003)

Maxwell wanted $40 ea. at first and a minimum $100 order, but let me have three for $100 even.


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## LoneRebel (Jan 30, 2003)

Cloud, what are the specs of the cap that you were getting a quote on?


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## radellaf (Jan 30, 2003)

The only sensible thing for these generator emergency devices is to enable the gen to work even if all else fails. The 2020 at least can do that. BTW, I thought the 3 LEDs looked about like 3LEDs should, similar to my Opalec Newbeam.

I also bought the S360 radio and will have to send that back unless I risk opening and changing the batt for at least regular caps if not supercaps. The damn thing has the battery right across the power to the radio, all else feeding in thru diodes.

So, few years later, shorted battery pack, wind the spring and nothing will happen. 

What's wrong with these mfgrs who build products with non-replaceable rechargeable batteries? Pisses me off.

The springless devices, as emergency devices, are just plain useless. Fun to play with, sure.

'course the real problem is that the person I'm getting the light & radio for has a psychological problem - no amout of batteries are enough for him to use a battery powered device in an emergency. Otherwise I'd get him an Opalec'd Mag or Infinity Ultra, a radio, and a pack of 24 AA batts to replace every 2-3 years.

His wife doesn't like the springs because of arthritis. Between the two of them I have no clue...if you don't use batts and can't comfortably crank...well? A good, expensive, charge 4AAs in a few hours, solar panel and a few NiMHs kept in regular use I suppose is the only answer. Short of a petro powered generator, but that has limited fuel (c.f. won't use batteries) so no go.


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## Clouddancer (Jan 30, 2003)

*LoneRebel*, 2.5V 100 farad, a bit larger than a zippo lighter. More specs that I don't understand are available for it (PC100E) on their site from the link I posted above for them. Their general application description for it mentions "small consumer products" and "extended power supply". Check it out and let me know what you think. In manufacturer quantities of several K they said about $20. Too bad a big distributor isn't carrying it.


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## X-CalBR8 (Jan 30, 2003)

That’s what I’ve been saying all along. For a super capacitor to actually be very useful in flashlight applications, you need at least 100 Farads and up. These 1, 5, & 10 Farad super capacitors just don’t hold that much energy which makes them mostly useless on anything more than one single Nichia white LED. At 100Farad each, there might be some real usefulness there.


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## X-CalBR8 (Jan 30, 2003)

Clouddancer: You do need a power regulator, but not for charging the super caps. You need the regulator for the sake of powering the LEDs after you charge the super caps. Your flashlight that you have may already have such a regulator, but I have a feeling that you will want to put something more powerful than that in there and increase the number of LEDs in there to really get the most out of those super capacitors. The LEDs will need a very precise voltage and/or amperage. Some power regulators work by regulating voltage, some work by regulating amperage and some do both. 

If you overpower LEDs then they will get what is known as thermal runaway. You may want to do a search for that on the forum for a more through explanation, but here is the simple version. When a LED heats up, it’s internal resistance decreases and it wants to pull more power. The hotter it gets the more power it pulls and so on and so on till the LED is ruined. This is why you really need a power regulator for LEDs. It is the only sure way to keep from having thermal runaway. This is an even more important factor with super caps because they have a much lower internal resistance than a battery does. Some mods using small AA and AAA (and in some cases even D) batteries depend on the internal resistance of the batteries to stop thermal runaway (note: this only works with Alkaline cells, not rechargeables because of the low internal resistance of rechargeables), but with super caps this will not work because super caps have such a very small internal resistance. It is even much smaller than with rechargeables. They will just keep supplying as much power as the LEDs can draw till they fry the LEDs without a power regulator. There are several people on the forum that sell power regulators just for the purpose of supplying a certain number of LEDs with a certain amount of power. You will also need to decide what type of LEDs that you intend to use before buying a power regulator. You can either use an array of Nichia white 3.6volt white LEDs or you can use a single Luxeon Star 1Watt LED. I can’t remember off-hand what voltage they operate at. You will need to look that up on the forum. If I were you, I would go with the white Luxeon star if you can get it. They are quite bright especially if you use optics with them to get a more concentrated beam. You first need to find out how much voltage your generator puts out to really know what all your options are.

The only problem that you will need to worry about with the super caps is that you don’t send a voltage to them that is higher than they can handle. You will need to hook a volt meter to the charging device to see what is the maximum voltage produced when you are cranking it at it’s maximum speed and make sure that that voltage is not higher than the capacitors can handle. If the peak is only very slightly over what the capacitors can handle, then you should be able to use a zenor diode with the proper break down voltage rating to shunt the over voltage away from the super caps. 

Another important thing that you will need to find out is whether your generator is producing direct current or alternating current. If it is direct current then your task is much more simple. If it is alternating current then you will probably have to build a full bridge rectifier to convert it to direct current. There may already be a full bridge rectifier in your light if your light does use alternating current. It may be integrated into another circuit though and so you may still not be able to use it. If you don’t rectify AC current then it could also damage the capacitors and for sure the capacitors will never take a charge because for every positive voltage you are sending it you are also sending an equally powerful negative voltage.


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## Clouddancer (Jan 30, 2003)

> Originally posted by X-CalBR8:
> *The only problem that you will need to worry about with the super caps is that you don’t send a voltage to them that is higher than they can handle. You will need to hook a volt meter to the charging device to see what is the maximum voltage produced when you are cranking it at it’s maximum speed and make sure that that voltage is not higher than the capacitors can handle. If the peak is only very slightly over what the capacitors can handle, then you should be able to use a zenor diode with the proper break down voltage rating to shunt the over voltage away from the super caps. *


<font size="2" face="Verdana, Arial">*Houston*, thanks very much. Why a zenor diode? Why if the peak is only very slightly over what the capacitors can handle? Where would the over voltage be shunted to? (I'm electronically challenged.) Wouldn't a resistor do the same thing in the same way as you say some of these guys use batteries? Or does that work by storing part of the power also? Are you forced to accept whatever the generator is putting out and do something with it? I'm guessing that there might be a wide variation from time to time of what the generator is putting out depending on how fast or slow you cranked it and difficult to be consistent. That worries me a little as to what you say about peak and the zenor. The Sentinel uses a little indicator light to show when you are cranking fast enough to charge right. Could that approach be used to tell you not to crank any faster? I like the idea much better of something much more durable than a warning light and that would limit the voltage no matter how fast you cranked, at least within reason, but that was one thought I've had. Isn't there such a thing as a voltage limiter or is that what a zenor diode is? How does this correlate to capacitors' ability to be charged much faster than batteries? How does that work when that's limited by their voltage? 

Am I correct in assuming that putting two 2.5V 100F ultracaps in series would be the equivalent of one 5V 200F or three for 7.5 300F? Would I be able to charge at those voltages or would I still have to stay down at 2.5? I think I asked Maxwell this and they said the former was true but just double checking.

Does someone have the formula for converting Farads to Watts?


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## evan9162 (Jan 30, 2003)

Cloud -

2 2.5V 100F caps in series would be equivalent to a 5V, 50F cap. 3 would be a 7.5V, 33F cap.

You can see how much energy, and thus, how much power over time is stored in a cap. The formula is:
Q = C*V^2

Thus, a 5V, 50F cap would have 1250J stored in it. Theoretically, drawing 1W, it would last 1250 seconds.

-Darin


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## James S (Jan 30, 2003)

A Zenor diode is nice because it has a very low resistance drop until you reach the rated voltage at which point it's resistance goes up considerably. So basically it will limit voltage when it's high and get out of the way as it drops below the limit. A resister will drop the voltage no matter what it starts out as.

I don't think you need to worry about a couple of extra volts in the charging process. At least not al lower current values. I've been charging my 2.5 volt ones from a hand pump generator that gives out up to 6v and they haven't popped on me. I also charge them for testing from 3v from 2 AA batts and they don't care. If you're going to be generating a lot of current from a more efficient generator or from some other supply then it becomes more important.

Didn't we just do the series parallel thing? when you put them in series it reduces the capacitance, but increases the voltage. 2 100F in series gives you 50F at double the voltage. At least that is how I read the math, please correct me if I'm wrong!

The power output seems to be very linear, so the voltage will start dropping off immediately and your lights will dim. I think it's going to be important to use some kind of up converter with them. Running a BB400 or some such from a 100F cap might give a decent runtime.

But there is a problem in charging them. If you think you can charge 100F from a hand pump generator I think you'll be disappointed! You'll be cranking for hours, depending on your generator. 

For example, I have a junky little hand pump job that outputs 6v when you really get it going. It took it 4 minutes of hand killing high power pumping to charge a 4F 2.5 volt array of caps to the point where the LED just began to glow. You can do better with better generators, but just because it's a cap and not a battery doesn't mean you don't have to put in the necessary power before you can get it out. I think it might be more interesting to build a "touch to charge" kind of thing. You can charge them in just a few moments with enough current. Touch it to the charger base for 10 seconds and get 2 hours of light or something like that.


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## Clouddancer (Jan 30, 2003)

*Darin*, I'm not sure I understand. Does that mean caps in series would store less power or that a single 2.5 100f cap would last longer than two or three in series?


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## Clouddancer (Jan 30, 2003)

James, whoa, I see! What do you mean "the charger base"? A rechargeable battery charger?


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## LoneRebel (Jan 30, 2003)

James S, what hand pump charger did you buy? Also how many amps does it output?


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## James S (Jan 30, 2003)

I picked up one of the $6.95 Dynalite Dynamo flashlights from Edmund Scientifics:

http://www.scientificsonline.com/ec/Products/Display.cfm?CategoryID=192967







I thought that for $7 I could afford to play with it. At full pumping it puts out between 6 and 7 volts. The light as shipped is mostly a curiosity, it has a regular flashlight bulb and it lights for about a second and a half with each pump. It's not really the ideal platform for a mod as it's rather cheap feeling. All plastic, the gears strip if you pump too hard (though they don't break, at least not yet) and the thing is rather noisy when you get it up to speed.

I hadn't tried to measure amps, but just shorting it across my meter shows 25ma, I can get it up to 27 by really pumping it





EDIT: oh, and it's output is AC so you'll need a rectifier.


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## LoneRebel (Jan 30, 2003)

James S, I was pondering buying that light a while back. 25ma is pretty pretty low though. I'd like to get more of a power horse than that...I think that light is more of a power guppy


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## James S (Jan 30, 2003)

Come to think of it, I had the meter set for DC. I would re-run the test for AC and see what it tells me but I'm already in bed (Ah, I love my 802.11 card



So I'll post more info tomorrow.

The one I got also differs slightly from the picture above. Not so that anyone else would notice, but those of us that like to take things apart would want to know. The top 2 screws have been removed and the case is glued together now. The bottom screw is still there, but you can't get it easily apart anymore.

SO no upgrading the magnets without potentially tearing up the case.


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## LoneRebel (Jan 30, 2003)

James S, WHAT??? Are you telling me you didnt take your flashlight and multimeter into bed with you? And to think I thought you were a flashaholic!


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## evan9162 (Jan 30, 2003)

> Originally posted by Clouddancer:
> *Darin, I'm not sure I understand. Does that mean caps in series would store less power or that a single 2.5 100f cap would last longer than two or three in series?*


<font size="2" face="Verdana, Arial">For a given voltage, yes. If you have capacitor A, it alone at a voltage V will store twice as much energy as two of capacitors A in series at the same voltage. But, putting the caps in series allows you to increase the voltage across the equivalent capacitor. 

It works because with two in series, the voltage across each is 1/2V. Since energy stored varies with the square of the voltage, you now have 1/4 the energy per cap. Since you have two of them, you're storing 1/2 the energy of a single cap.

You put two caps in series if your working with voltages higher than what one cap alone is rated for.
-Darin


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## X-CalBR8 (Jan 30, 2003)

Clouddancer: I would help in answering those questions, but it looks like the fellas beat me to it. Thanks for the help guys.


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## Clouddancer (Jan 30, 2003)

Okay, got it. Thanks. Should LEDs be in parallel? Do you simply add up their rated ma to tell how much power you need or should they be in series?


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## Clouddancer (Jan 30, 2003)

How is it that capacitors can be charged much faster than batteries when their voltage is limited? They will take higher amps than a battery? What is going on there?

Could I run an indicator light off the dump side of a zenor diode to tell when I'm overdoing it?


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## Clouddancer (Jan 31, 2003)

> Originally posted by Nerd:
> *I think I remember someone saying that 1 farad capacitor would power a ARC AAA for 3 mins before going into moon mode. Let's take it from here.
> 
> 1 farad @ 2.5 volts = 60-100 ma current draw for 3 mins*


<font size="2" face="Verdana, Arial">Does that mean a 100 farad capacitor would power an ARC AAA for 300 minutes?


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## Clouddancer (Jan 31, 2003)

> Originally posted by James S:
> *LoneRebel, I looked up the math for capacitors in series and parallel. When you connect capacitors of differing values in series the value of the resulting string comes out to just less than the smallest capacitor. Here is the example:*


<font size="2" face="Verdana, Arial">*James S*, Maxwell's site has a calculation formula similar to yours for determing the size of capacitor necessary for an application. Can you take a look at it with LED application in mind? It can be found under "Application Notes". On the phone Maxwell also emphasized the importance of "Cell Balancing" found in the same place, but the notes discuss it with reference to parallel configuration rather than series such as two 2.5s for 5. How important would this be for series use? The Maxwell rep also said I wouldn't need anything to regulate the discharge to the LEDs as the caps would only discharge according to the draw. My impression from the forum however, is that a regulator is a good thing for steady power, right? Would I need resistors on the ground side of the LEDs to keep the caps from blowing them?


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## X-CalBR8 (Jan 31, 2003)

Clouddancer: Yes, you would connect the LEDs in parallel and you would add up the Ma draw of each individual LED to get the total amount of power that would be consumed. Make sure you get your positive and negative connections right on the LEDs because as you may or may not know, LEDs can only work if oriented the right way.

The capacitors can accept a charge practically as fast as you can throw it at it, but batteries are very limited on how fast they can be charged because of their internal chemistries. In other words, when you charge a battery, there is a chemical reaction taking place that can only take place at a very limited speed, but when you charge a capacitor, it accepts the electron charge directly so it has almost no limitations on how fast it can be charged which is a very useful quality when dealing with a device that likes to charge very quickly like a hand crank generator. 

That’s why I believe that super caps are ideally suited to this type of application. In fact, this is the very thing that super capacitors are doing inside of electric cars these days. When you brake the car, much of the kinetic energy is converted to electrical energy (through a generator) and is stored in super caps. Then the energy that is stored in the super caps is the energy that is used to give the car the extreme boost of energy that is required to get it moving again from a complete stand still. They do things this way to make the car more efficient and also to make the batteries last longer because it is very taxing for batteries to put out that much energy that quickly but it has no harmful effect on super capacitors at all.

The trick with the indicator light might work, but I’d better leave that question to someone that has tried it because I’ve not tested a setup like that before. I’m not sure what the results might be.


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## Clouddancer (Jan 31, 2003)

What I have so far as a possibility is removing the spring and reels from the Freeplay and leaving the gearing to the generator in place. In place of the spring and reels installing two 2.5V 100F ultracapacitors about the size of zippo lighters, in series for 5V 50F. Then putting a 4.5V zenor diode across the generator terminals or caps and installing a regulator board between the caps and LEDs. The generator manufacturer says it will "output" up to 1.5 amps. The Freeplay switch in the off position disconnects from the circuitry which in that position could be used by the charging circuit instead. The large first gear (8.5cm dia.) off the crank handle turned by the spring now turns very slowly but through mechanical advantage of two more gears turns the generator much faster. Without the spring then, I could easily spin it much faster by hand to charge the caps. Now the factor it seems to consider is whether the generator is appropriate. RF-500TB Generator


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