PeterDove

Hi All,

Can anyone explain how you can get a 1.2V battery to power a 3V LED ? Is there a way to step up the voltage to power the LED?

Thanks

Peter

PeterDove

BTW, thats how do I make 1.2V DC up to 3V DC - the only examples I have found on the web so far are from AC to DC

em2006

bloody-orc

search for joule thief on google

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kchriste

It can't get any easier than this:

http://cappels.org/dproj/ledpage/leddrv.htm

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Top Cap

If you want to just flash the LED then the LM3909 can be useful

http://www.reprise.com/host/circuits/flasher.asp

Also see:-

http://www.qsl.net/yo5ofh/hobby%20ci...d_circuits.htm

Les

k7elp60

The LM3909 may be difficult to obtain as it has been discontinued.
The attacted schematic should work fine

Attached Images

white Led drive.GIF (5.7 KB, 38 views)

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audioguru

The LM3909 has not been made for many years. There are discrete replacement circuits for it on the web. I have seen voltage doubling circuits that use only two transistors but I didn't save one.

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Uncle $crooge

ante

Hi Guys,

This one is built and tested, works on a single NiCad cell down to 0.85V.

Attached Images

1cell.png (34.5 KB, 36 views)

Top Cap

Gee sorry Guys, had no idea the 3909 had been discontinued. I still have one in its wrapper from RS (300-372) I notice that they have discontinued it from stock. That's the trouble with getting old, all the devices you used to have fun with at an earlier age are now obsolescent, I don't suppose it will be far off before I join them
Les G4CNH

The Mad Professor

Oh I would not worry Top Cap , I here there is a guy in England who still makes a tidy living servicing punch tape readers and three computers built using discrete 7400 logic chips that run some multi axis jig borers.

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RODALCO

Build the circuit for the Joule Thief ( google )

only small coil to be wound (about 20 turns bifilar) and one transistor required plus LED !

I built a couple of them and they drain a battery down till 0.35 volts.

Your 1.2 volts application will be perfect to drive a white or blue led at the 3.4 volts required.

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RODALCO

http://www.emanator.demon.co.uk/bigclive/joule.htm

Here is the link and the very simple circuit with all details how to built it.

Good luck

raymond

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There are more ways to get to Rome.

Electricity, Electric clocks, Meters and Trains are great.