Colour Changing Night Joule Thief

I got this inquiry from a teacher who teaches high school kids electronics - can we have a cool kit like Aurora mini 18, in a simpler and more affordable format? I suggested Night Joule Thief, but the teacher felt that it wasn't sexy enough for the kids. (ur... you know what I mean.)

So I combined the multi-color LED and Joule Thief in one, and got Colour Night Joule Thief. It's a mood lamp version of Night Joule Thief.

 

Step 1 Features

Here are the highlights of the Colour Night Joule Thief.

    * Compact & streamlined design
    * Uses only one AA battery (or any 1.5V battery you can hook up to)
    * Easily adaptable to different size batteries - hook up holes to attach home made clips
    * A multicolor/color changing LED
    * Automatic turn on via a light sensor (adjustable sensitivity level)
    * Energy efficient - works even with a run-down battery, down to 0.6V
    * Makes a great little mood light

Comments

[lgore93]

Do you think I could maybe replace the PCB with a couple of popsicle sticks glued together? I know that sounds kind of ghetto, but I'm looking for a very inexpensive project to do in class. It would be much cheaper if I could make a working model on popsicle sticks. I know it wouldn't look as professional, but things would be much easier.

[ledartist]

Yeah, you should definitely try that. Please post the result!

Aki

[lgore93]

Okay thanks! One more question which is probably obvious... The smallest photoresistor I can buy from the site I usually order from is 5k-0.5M ohm. Would the circuit work with this difference? I realize 2k ohms is a significant amount, but is it really that much on this scale? I admit that I know much less of electronics than I would like to, but I love learning and building new things. Thanks for your help.

[ledartist]

That will probably work. I'd just try it, maybe on a breadboard.

Aki

[lgore93]

My parts came in yesterday, and I built it. It's not the prettiest thing in the world, but it works very well! I decided to use a piece of cardboard instead of popsicle sticks since it allowed for some less than... perfect wiring. Also, I found out I was out of electrical tape so I had to substitute duct tape in. Haha

[ledartist]

Umm... You are good.

[ciliar]

Aki, you are a star - soon to put Colour Joule Theif into action! Keep you posted!

[ledartist]

Thanks!
Yes keep me posted.

Aki

[markallie]

In the pdf version of the schematic an MPSA05 is listed as a choice for the PNP transistor, Q1. It is an NPN transistor.

[ledartist]

Thank you for pointing this out. I've corrected the error.

Aki

[GASSYPOOTS]

how bout a self charging/ no batterys needed after 1st charge

[64bitgenius]

unfortunatly, I don't think thats realistically possible. the reason for that is that it is going to lose energy no matter what. if it were 100% efficient, it would be possible, but it's not.

[sageserver]

Can another LED be used in place of D1? or is the voltage difference too much? Very instructive instructable.

[ledartist]

D1 is there to rectify the voltage, so it has to be regular diode. LEDs have too high of forward voltage drop.
If you wan to drive two LEDs, you can simply add another LED in series to D2. The brightness will go down a bit, but it will still work.

Aki