Introduction: How to Convert Fluorescent Starter to Thermal Switch

Fluorescent starter is essentially two bimetallic strips in a sealed glass capsule, with a small gap between them.

The principle of this experiment is Metal expansion and contraction .

1-  12 volt CPU Fan.
2-  12 Volt supply.
3-   Fluorescent starter.
4- Candle.

1- Break the starter glass and try to not damage the metal inside (Take all safety precaution when you do that to avoid any injury).
2- Make sure that there is a small gap between two metal as shown in attached picture. 
3- Connect the circuit as attached in the first circuit diagram and fix the starter about 2 cm above the candle.

When the candle lighted up ,the starter metal  will expand and attached together , the fan will turn on  and turn off the candle ,the two metal will de-attach and turn off the fan.

Note that CPU fan is a brush less dc motor and it will not cause spark in starting ,the spark can damage the metal and it will not work for long time ,so if you connect a load that take more current  and cause a spark in the starter you can use transistor showed in the last diagram to avoid this issue .

if you find this tutorial useful to you , please vote for it in the Electronics Tips & Tricks contest.
Many thanks




marknluke made it!(author)2013-10-16

it is very good and i made it for my school exhibition i got first thank you very much for this project

Husham+Samir made it!(author)2013-10-16

You're most welcome.

astral_mage made it!(author)2013-09-19

should try it with a smaller fan? and or angle the fan so it doesnt blow the candle out?

ToXiCATOM made it!(author)2013-06-09

your rock Husham Samir!!!

ynze made it!(author)2013-01-06
Love it! You made a "most useless machine in the world" (see vid and somewhere on this site...) while demonstrating a clever thermo-switch. Thumbs up!

Husham+Samir made it!(author)2013-01-07

Nice video ,I love it ,thank you for sharing.

DIVYA+GARG made it!(author)2012-10-02

very nice .................................but why did you use TRANSISTOR in this project ............?

Husham+Samir made it!(author)2012-10-02

Thank you Divya
if I am not using the transistor ,the circuit will work but a spark will happened every time the metal attached and it will damage the bimetallic strips ,so the purpose from the transistor to increase the life time of bimetallic strips.


iceng made it!(author)2012-07-01

Good project, excellent thinking out of the box ! !


Husham+Samir made it!(author)2012-07-03

Thank you.

francisdsa made it!(author)2012-06-28

Nice info. i think by modding the gap between the terminals, once can make a parked car cooler using a similar circuit. it will automatically start the fan and rotate the air inside the car when the temperature rises and shut off when cooled.

can you do a test and measure the temperature when it starts bending? so we can accordingly know when it switches at what temperatures..


Husham+Samir made it!(author)2012-06-29

Thank you francisdsa
I have tried your suggestion but unfortunately it is not efficient because the two metal is too small and not easy to twist them to get the required setting .
for a project like parked car cooler I suggest you to use LM35 temperature sensor with op-amp comparator .

rimar2000 made it!(author)2012-06-28

Very interesting, thanks for sharing.

About This Instructable




Bio: Electrical Engineer
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