Reptile & Amphibian Forums

At it again, this time I did a nice one IMO. This is an ON/OFF controller using an STC-1000 module (Amazon.com) and an RL series box from Hammond (sized 4.92x3.15x1.97 deep also on Amazon or Mouser).

I use this and plug a table-top lamp dimmer into it, then the heater into the lamp dimmer. Works quite well. We will see how long the STC-1000 lasts. They are only $16 and made in China.

While I am using these on my animals, I have a trusty Johnson Controls T-stat in series just in case.

I was looking at those a few days ago myself. I may have to give it a try.
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Reptiles Make The World Go Round.

Thanks Randall. The STC-1000 is an amazing little unit for the price. And from what I can tell thus far, it works as well as more expensive controllers provided the user wires it correctly and takes care to use reasonable electrical common sense.

It is more expensive to buy the plastic box, power cord, fuse holder, strain relief and wire than it is to buy the controller unit itself. I have never found DIY to be less expensive, but it is fun and educational.

Amazon will always have poorly-rated product comments by people who use the product incorrectly. For example, do not use the STC-1000 to control a 3HP motor. That is just not good judgement. But for heat pads or heat panels in reptile cages, no problem.

Since you are familiar with this, and this will be my first go at it, tell me if this sounds reasonably doable.

I'm going to see if I can find a simple chime/alarm/buzzer. I will then wire it into the cool circuit so I can set it to sound if a high temp is reached. Seems like a fairly easy way to incorporate an audible warning if something wonky were to occur.

What is your thought on this? Any suggestions?

Thanks.
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Reptiles Make The World Go Round.

i will check for you. These are dual-stage. When the heat relay de-energizes, the cool relay energizes, but I do not know if it does so immediately or at the set point plus differential value (I think it does so at the sp differential). You would not want the alarm to sound when the heat relay deenergizes because it would do so often. I'll try it myself

I appreciate that, the idea of making this after seeing you making them for years actually has me a bit excited. I haven't wired anything up myself in years (not counting rheostats since they are so basic).
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Reptiles Make The World Go Round.

I set the setpoint to 80 deg and the differential to 2 deg.

Heat pad temp started at around 75 deg. Heated up to 80, then the heat relay de-energized. The cool relay was still de-energized.

The heat pad began to cool, when the unit read 78 deg, the heat relay kicked on.

Temperature = setpoint (80 deg) - heat relay off

Then I tried the cool circuit. The summary is this:

Temperature >= setpoint plus differential (82 deg) - cool relay on
Temperature

Cool relay function:

Temperature >= setpoint plus differential (82 deg) - cool relay on
Temperature

Cool relay function:
Temp is greater or equal to setpoint plus differential (82 deg) - cool relay on.

Temp is less than setpoint (80 deg) - cool relay off.

So, you may want a 2nd controller just for your alarm if you don't want the alarm sounding sometimes on a very minor temp spike, especially if using a 1 deg differential.

Thank you for doing that testing. I'll have to consider building an alarm from a 2nd unit.
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Reptiles Make The World Go Round.

I'm going to order one of these and give it a try, what sort of temp window are you able to maintain with it? I'm probably going to build it with the intent of using it on a rack running 11" flex underneath vision boa tubs. I have a self built dimmer I'll run in line with it as well, but will probably test it for awhile without the dimmer to see what variances I get.
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Reptiles Make The World Go Round.

Randall - in my setup it holds within 1 degree easily. The use of a dimmer allows "fine tuning" so to speak such that the controller relay does not cycle on/off as much. Also, make sure to set the differential to 1 degree, I think the default is 3. Also, with resistive heaters like heat tape, pads and panels and lamps, you don't need the time delay (that may be just in cool mode).