DIY Rheostat (dimmer) for temp control

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Originally Posted by jpman78

The prebuilt dimmers (e.g. walmart $10 mentioned above) can goto one or more devices if you plug in an extension cord.

The real limitation with the walmart model is that you can only have so many devices hooked up to it before you overload the dimmer (up to 300w worth).

For about the same money as the pre-built model you can build your own that will handle twice as much wattage (600w).

Really the walmart model is best for most small applications but I like to build things rather than buy sometimes. That and I wanted a dimmer with a ground plug for my 1500w ranco on/off thermostat.

For what you want you would need a thermostat (on/off or proportional) to shut the heat off at a certain temp and turn it back on again when it cools off. The dimmer basically just keeps the same temp difference.....not the same temp.

So if you have an 80 degree room and set the dimmer so that the hot spot is 90 degrees the dimmer essentially is set to +10 degrees.

So if the room heats up to 85 degrees then the hot spot will change to approximately 95 degrees if you don't change anything on the dimmer....same +10 degrees

Hope that makes sense :)

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Makes perfect sense, dimmers change the heat but need to be contorlled by you. What I am looking for is a "Set it and forget it thing" I currently have 2 dimmers from home depot, one for hot side and one for cold side. They work fine, but for instance when I go to sleep at night, by body heat can change the temperature in the room to at least 4 degrees higher, thus increasing the tempertaure in the tank 4 degrees high, just as you said. What I was looking for is something that will keep a constant temperture in the tank no mattter the temperture in the room so if I set it at 82 and my room increase 10 degrees i wont get a 92 degree, I hope this is understandable. :)

Will this type of dimmer control an under tank heater? If so, what is the safe temp for a UTH?

Yes it will control you uth, safe temp to bp 92-94*, they work best if your room temps are stable, if your room temps are not stable, you will have to monitor your thermostat carefully.

This is my plan for a dual rheostat with two constant 110v plugs.

It doesn't seem to be very good at controlling the temp of my UTH. Any ideas?

I have it set at about 10 o'clock, (8 o'clock being full "off", 4 o'clock being full "on"). and the surface temp of the glass above my UTH is still reading about 100*F.

http://i110.photobucket.com/albums/n...980/Snake2.jpg

edit: ignore the orange dots, I was out of wire nuts and was planning to raid my dad's garage...I was counting how many "at most" I'd need.

Dimmers work great it an area of constant temperature (dedicated room that is heated/cooled to 80 degrees for example) if you are in an area of variable temps the dimmers will allow that amount of variable as well (if you set a dimmer system to be correct at a room temp of 68 and the room goes up to 73 the uth will also rise by the same 5 degrees. They are great in a controlled area but in a regular room that changes (day and night season to season) a thermostat is they only way to adjust to that variables. Proportional ones will not allow the surfac temp of the uth to go much higher than the set temp non proportional will click on and off 100% and 0% That is likely what your problem is turbose

I check my temps around the same time everyday..after work..4-5pm EST.

Should I hook the whole setup into a thermostat?

Current temps:

UTH glass: 98*
In viv: 88*
Cold-side glass: 72*
Hot-side glass: 74*

She hasn't left the cold-side since I put her in the tank....