DIY Fan temperature controller

[ndsmerk]

I'm working on building a diy fan controller to cool off my tank this upcomming summer. I'm using a Honeywell house thermostat. I extended the thermosister with some wires and siliconed it into a test tube so my catfish can't bite it. The thermostat will be left on the heat cycle and will be connected to a 12v DPDT relay. One side of the relay will provide power to the fan(s) and the other will turn off the heat just in case it gets stuck on. It seems to have a 2 degree swing. Since I have my heater set to 77, i'll set the thermostat to 79, so the fans will turn on at 80 and cool till it hits 78.

This is the link that finaly made me decide to do it...
http://www.reefcentral.com/forums/showthread.php?s=&threadid=462229&perpage=25&pagenumber=1

What does everyone think here?

P.S. I got a 3v wall wart to power a small fan in my lightstrip so it's running slow and quietly. That should take off a little extra heat...

 

[w6wat]

I'd be interested in a diagram of what you're doing. It sounds great.

Thanks,
Wayne

 

[ndsmerk]

A thermostat uses a power signal from the heater, it's supposed to be 24 volts i guess. It switches the voltages on and off when needed. This activated and deactivates a relay. I'm going to use it on the heat cycle and when the relay deactivates, then my fan turns on. It's rather simple, a diagram can be found on that link.

The problem I am haveing is that the temperature reading seems to be swaying a couple degrees while my thermometer is constatly reading 77-78F. It's about all I can ask for though. Maybe I should have bought a rite-temp instead of a honeywell. My relay should be here monday or tuesday. I can wire it up and try it out then.

 

[1oooop]

o boy o boy... i have a circuit for you here it doesn't control heaters tho... sorry... it will control a relay... which you can use to power a heater...