Spring Powered

[Clouddancer]

Does anyone know whether an LED flashlight could or could not be powered directly by a handcranked wound spring like some of the survival types? I think that type simply recharge the batteries for a short time, but not sure. Do batteryies really need to be in the circuit? To stabilize the voltage & store the power perhaps? Or could other means be used? Seems like with the right gearing and generating components, LEDs, it could be made to run for quite a while without rewinding. The Sharper Image survival light & radio claims the radio will run for 50 min. on one wind, if that's relevant.

 

[Icebreak]

Hey Clouddancer-

I was about to say something about spring power but revisited your other post and see there is more to it than I thought.

http://www.candlepowerforums.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=003759

 

[EMPOWERTORCH]

Clouddancer,
Clockwork electrical generators were piomneered by Trevor Bayliss, resulting in the famous Baygen clockwork radio. Another firm, Freeplay, have produced a similar product with a built in torch.
Logic dictates that an LED torch is certainly feasable using clockwork (spring powered) technology. There are a number of handcranked torches with filament bulbs which should be easily convertable.
The problem with clockwork power and small dynamos in general is that the speed can only be governed roughly, unless you are of course using an escapement mechanism as in a clock, but this is not energy efficient. The flicker of an LED due to the irregularities in the supply would be annoying somewhat... in filament bulb HPT's (human powered torches) the heat in the filament smoothes out the undulations in supply to a certain extent, but in an LED HPT the flicker would be much more noticeable.
The answer is to put a very high value capacitor in the circuit. Developed for the phone industry as a memory backup, very large value capacitors without the bulk of a huge electrolytic have been realised and produced. These have found thier way into the "shaker torch", an innovative HPT which generates its electricity from a simple plunger/weight generator. As the torch is shaken, a powerful bar magnet passes through a coil of wire, and the gemnerated electric charfge is stored in one of these very high value capacitors. This is dischrged through an LEd or a set of LED's, producing light, about 1/2 an hour for 30 seconds of shaking.
For a rotary/spring generator HPT, the capacitance need not be so large, but the principle is the same. In any HPT, the power source must be sufficient to operate the lamp assembly, (LEd or otherwise) without overloading either the generator or the lamp. Regulation is best achieved by using solid state regulators or Zener diodes and resistors, both of which will clamp the supply voltage down to a safe level for the LED.
Much of what I have described also applies to dynamo bike light circuits, too!

I hope that I've been of help. Other CPFers will be able to dig out links for the HPT's I've described earlier, complete with pictures, etc....

Matt.

 

[Clouddancer]

Excellent Matt. Yes, very helpful. Thank you. I'm wondering if the Freeplay 2020 doesn't already use that requlator circuitry since the specs say it will run the LEDs directly off the generator. Evidently the short 10min. run time is due to the size. I imagine the cost is up there in part due to the solar panel. I hope some of those HPT links come up. I would bet somewhere for some other purpose there are larger spring powered DC generators out there. Sounds like something just begging for a custom build.

 

[B@rt]

Here is an example, there are many more to be found , but be aware that most are of dubious quality.

Dynamo

 

[Steelwolf]

I thought Freeplay and BayGen are essentially the same company, just something to do with legalities and names and that one is the commercial manufacturing part and the other is the design part that created the spring-powered equipment as part of a 3rd-World assistance project.

Anyway, the Freeplay 2020, IIRC, has no solar panel. The LEDs run straight off the spring. The 10min run time is how long it takes the spring to fully unwind from fully wound position. The LEDs don't have any perceptible flicker because the unwinding spring keeps the generator speed constant and what little fluctuation is further smoothed by a small capacitor hooked up between the output terminals of the generator. But between the generator and the LEDs, there is no proper power storage unit. The incandescent bulb is powered by a completely separate battery system that is not rechargeable via the spring-generator system. The spring unwinds slowly because of a governor system (those gears you see in the flashlight or radio).

The systems that I am looking in to modifying are the Freeplay S360 radio and the Freeplay FPSL flashlight. They are out of production, but I bought mine a while back when my local electronics/hobby stockist was having them on sale. The FPSL looks like it may be the easiest to mod since the spring-generator and batteries are connected, and there is enough space to put in extra stuff (like a solar panel, banks of capacitors, regulators, etc.) The S360 has a solar panel already installed but has very little space for anything extra. The difficulty with the mod is that the batteries are 2.4V and that the spring-generator may be set up to deliver only 3V to charge them. And also, opening up anything with a wound spring in it is a little risky.

BTW, I'm not sure about the newer models being offered by Freeplay. The Sherpa, Sentinel, and Outrider seem to have discarded the spring. Instead, the user has to wind at a constant and optimal rate, which is shown by a couple of indicator lights. A step backwards, IMHO.

Also, there are quite a few forumites who have modded a standard, hand-cranked incandescent flashlight which doesn't have any power storage components like batteries. I did one myself. Changed the incandscent bulb to an LED, put a bridge rectifier to turn the AC output of the generator to DC, then put a supercap in between the LED and the generator to smooth out the power flow and store some additional charge. Crude, but works. I'm trying to see what else can be done to improve it in terms of power output, light output and efficiency.

 

[Clouddancer]

Good information Steelwolf . Thanks. My impression is that the way to go is to abandon the current bodies and create your own with a cannabilized generator so you have the freedom to use a larger spring.

 

[B@rt]

I'm not sure yet if leaving out the spring in the Sherpa is a step backwards. Keeping things simple makes it easier to make it reliable. Trevor Bayliss' original intend was to provide radio and light as economical and reliable as possible, since a lot of people have to spent a ridiculous amount of their income to buy batts...

 

[Clouddancer]

Yes, that's why I would like to build my own with a cannibilized generatror and extra long duration spring.

Steelwolf: Also, there are quite a few forumites who have modded a standard, hand-cranked incandescent flashlight which doesn't have any power storage components like batteries.

<font size="2" face="Verdana, Arial">Can anyone recommend a generator?