I'll be continually monitoring the temperature inside the bin of one of the animals, and adjust the heat output accordingly, the further off from the target temperature the higher the heat output.

The flexwatt simply slides into pre-made slots in the animal rack, under each bin.

sounds like a lot of thermal mass. You could probably PWM these in the frequency of tens of seconds, with an SSR or wetted relay.

 

sounds like a lot of thermal mass. You could probably PWM these in the frequency of tens of seconds, with an SSR or wetted relay.

I googled this flexwatt thing. it's like a fabric or a mesh of wires. I would say like a screen door made of lightbulb filament. not sure how much thermal mass that would have but I assume not much

 

True, there is about 1-2 inches of bedding (Shredded wood) plus the plastic in the bin between the heat source and the animal (And where the probe will be).

It's going to take a whole lot of testing to see how fast the heat reaches through the thermal mass, that will have to be the baseline for adjusting the heat output.

Preferably I should be able to switch between flexwatt and heatlight, so I still have some research to do, but first step is to be able to reliably control the flexwatt for proper heating of the cages.

 

The problem with flexwatt elements is that they can not take much heat. So they must be covered with materials that let the heat out. Or else they will overheat. You should contact the vendor, as they may help you doing the correct calculations. It may be that your bedding of Shredded wood may isolate to well so the elements overheat. Have you given this any consideration. You may solve this by placing the flexwatt elements in the roof. Depending on your roof isolation this may be a solution. Mounting in roof is also recommended by flexwatt as a solution.

 

Ok, flexwatt is one of the standard things used in animal caging.
The manufacturer we use have routed channels as standard in the rack, and they're used with wood bedding or newspaper, together with a proportional digital thermostat (All of which we have, of course) for our animals.

They don't take damage if they go full blast now and then, only if you let them sit att full output for too long.

I'm not changing how they're supposed to be used, I'm just looking at making my own thermostat to control them with.