Building thermostat controlled fans

[Tal]

Hi,
I have the following parts:
- 2 fans 12V 0.12A each
- 1 PNP transistor TIP125
- 1 Thermostat switch which disconnect when temperature goes above 40 C
- different types of resistors
- 1 power source of 12V 0.5A

I want to connect this parts so when the temperature goes above 40 C the fans will start to work, I tried to connect the emitter of the transistor to the power source (+) side, the collector of the trsnsitor to the fans (+) side, and the base to the power source (+) side through the thermostat switch. Yet the this circuit is not working. I attached a diagram. can someone tell me what is worng or missing?

 

[audioguru]

You have the fans connected in series so each one gets only 6V and barely runs. Connect the fans in parallel instead.
You have the thermostat turning on the transistor when it is cold and turning off the transistor when it is hot.

Instead, use the thermostat to short the base to emitter of the transistor to turn it off when it is cold then the base resistor turns it on when it is hot.
The TIP125 is a darlington with TWO transistors making a high gain. It conducts well with an 820 ohm base resistor that will heat with 1/8th of one watt so a 1/4W resistor is fine. It doesn't need 270 ohms that heats with almost 1 Watt.

Try it like this:

 

[Tal]

worked like a charm,
thanks a lot