Simple thermostat circuit to control seed propagator

[Jules]

I have a heated propagator inside a greenhouse to aid seed germination (5Watt 240V). There is no way of controlling its temp. I need a simple thermistor thermostat circuit to switch heating on when air temp falls in evening, and switch heating off when air temp rises. I want to run this circuit from a simple capacitative mains dropper power supply, so it doesn't need transformer or batteries.
Any help please? Thanks

 

[Nigel Goodwin]

Use a mains transformer!, capacitive droppers are pretty poor things!.

 

[Jules]

thermostat for propagator

Very little space or cash for transformer. I do have a lot of mains dropper caps though. I was thinking of a Triac to conrol the mains supply.
Any ideas?

 

[Nigel Goodwin]

Have a look at , the 'Auto-Fan' should do what you want.

But, in my opinion, if you have to ask for something as simple as a thermostat you shouldn't be messing with live mains and capacitive droppers!.

 

[Fenris]

Pardon me can i ask ,re that fan circuit. could you take the relay
out and directly control a PC Fan? the one i have is rated as;
12VDC
input current 0.08A
power 0.69W
if i changed R1, P1 and TH1 round would it then work in reverse. (if its hot it turns on, when its cool it turns off)

Regards

Fenris