Art and Technology are Friends

Night Joule Thief – LED Night Light Kit

Joule Thief circuit is combined with an ambient light sensor – Night Joule Thief is a little night light that keeps going with just one battery for weeks! Two white LEDs light up surprisingly bright.

* This is the original version of Night Joule Thief that uses white LEDs – not to be confused with the new color changing version.

Please view the instructables for technical info and assembly steps.

*** NOTE: The color of the PCB will be green instead of purple shown in some of the pictures. ***

*** Purchase Here ***

21 Responses

  1. Dan Maker

    Are these still available? I have a group that would like to build them.

    March 9, 2014 at 7:54 pm

    • Yes! They are available and still very popular.

      March 9, 2014 at 8:14 pm

  2. Brian Compton

    Will you ever offer these Open Source?

    February 15, 2014 at 7:33 am

  3. I don’t offer the kits assembled, unless otherwise noted. I can do it for you but there will be $70 charge for assembly.


    October 9, 2013 at 12:30 pm

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  6. Tim

    Hello, I was wondering if you can replace the light sensor with a switch. If so what will happen to the sensor adjuster will it adjust light level or does it need to be removed when remove the light sensor?

    May 10, 2013 at 9:36 am

  7. Thanks for making the kit available.which kit are avialble they are very use full for me to make my project



    October 4, 2012 at 10:32 pm



    October 4, 2012 at 10:30 pm

  9. John

    Awesome kit! It says it is out of stock though with an estimated arrival of March 16th. Is that arrival of new kits to you or if I place an order today the estimated arrival to me?

    Also, I’m an Electrical Engineering student and I’m going to be buying this kit as part of a research project for my circuits class. We’re to analyze a circuit and this one seems simple enough while still very interesting and nifty enough to hopefully impress my professor. I just wanted to make sure you don’t mind me using your circuit as I will give proper credit.

    March 5, 2012 at 9:38 pm

    • Thank you for your comment!
      The kits will most likely to arrive to me by March 16th. Backordered kits will be shipped at that point. So if you are in the US, it’ll take 3-5 days after that to arrive to you.

      Of course you can analyze the circuit all you want. Yes the credit will be good.


      March 5, 2012 at 10:23 pm

      • John

        Hey! So I just ordered the kit and noticed you’re not really specific as to the specs of the led’s that are included. I’d like to model this in multisim so could you please tell me what the operating voltage and current are of the LED’s?

        March 20, 2012 at 1:38 pm

        • Hello John,

          The LEDs used here are very typical 5mm white LEDs in water clear case.
          Forward voltage is 3.4V typical at 30mA current.
          If you use “Super Bright” cool white, they should look the same.


          March 20, 2012 at 1:46 pm

    • Jan Stiener

      John – I have analyzed this circuit and one thing that would be good to present to your professor is that the circuit is terribly inefficient and vast improvement can be made by increasing (or smoothing) the duty cycle of operation to 50%. Right now, the duty cycle is approx. 10%, but its burning up the same peak current that goes through the LED string on the ON time during the OFF time through the boost switch, so its effectively running CW with only 10% of energy delivered to LED and 90% being delivered as waste heat through switch, Q3. Modify the inductor value to reduce peak current, and change duty cycle to 50% so same apparent brightness of LED is obtained using less peak current, but with the higher duty cycle.

      Also, if you look up Horowitz’ Electronic Encyclopedia, this circuit is shown in there (minus the light sensor part)

      June 15, 2012 at 8:14 am

      • Jan,

        Just to be clear, in your comment there are a few incorrect assumptions and misunderstanding of how inductors work.
        While this circuit is not super efficient, it’s much better than 10% efficiency. The short bursts of current that drives LEDs is not wasted by any means – it does get used by the LEDs.
        During the 90% “on cycle” the energy is being _stored_ in the inductor, small portion of that is a loss due to the resistance and transistor C-E saturation voltage.
        Finally, the output voltage of boost circuit is proportional to the duty cycle – at 50% duty you can only get double the input voltage (under the ideal condition) not the over 6V being generated in this Joule Thief circuit.


        June 24, 2012 at 1:40 pm

  10. Victor

    Where can I get the 1.5v C/D battery clips for the “Joule Thief LED Night Light – Kit & PCB”, as it only shows the 1.5v AA clips with the kit?


    February 27, 2012 at 6:23 pm

    • I just made the clips (seen in the video) with a paper clip. There are holes on the PCB to accommodate this.
      Otherwise I don’t know where to get C/D size battery clips…


      February 27, 2012 at 6:27 pm

  11. Chanda

    I have never attempted to solder on a circuit board before. Do you have a fully assembled Joule Thief for sale? If so, I would like to purchase one. Can you tell me the price and shipping?



    January 23, 2012 at 7:05 am

    • I can assemble the kit for $10/kit (in addition to the kit price). Not sure that makes sense to you, but it takes time to assemble the kit, so…


      January 23, 2012 at 12:33 pm

  12. David

    The Joule Thief kit looks like a great project for a novice (that would be ME). I am afraid to use paypal, based on personal experience. Is there a surface mail option to send payment? I can provide a personal check or a money order. I understand that surface mail will be slower. I am not in a hurry.
    Thanks for making the kit available.

    September 5, 2011 at 10:19 pm

    • Hello David,

      Sure, you can send a money order via snail mail. Be sure to include the shipping address and your email address for contact.


      September 5, 2011 at 10:33 pm

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