Digital Differential Thermostat

Digital Differential Thermostat for your solar project. I use one of these to trip the pump on my solar hot water collectors, but they have many uses. Building a solar hot water system? Want to recover the heat from you attic in the winter? This will work perfectly to turn your pumps or fans on and off.

- SPDT relay output. This means you have "normally open" and "normally closed" outputs on the board. Useful if you want to turn things OFF at a certain differential temperatures and not just turn things on.
- Output relay is rated for 250VAC and 5A. However, if you are controlling line voltages I recommend you use a solid state relay or an AC "contactor". Those types of devices are designed for line voltages and have been tested for same.
- NOTE: I do not recommend you use this for line voltages, and if you do you assume all risks yourself.
- LCD display of current sensor temperatures, current differential, and differential setpoint.
- Freeze protection, will not trip relay if either of the sensors are disconnected, or either read below freezing. This can be disabled.
- User selectable Celsius/Fahrenheit readout.
- Will run from just about any "wall wart" type power supply.
- NOTE: This device does not *output* any power, think of it as a switch that turns on and off. You will need to supply the power for your pump/fan.
- Digital Differential adjustable from 1C to 40C

- input power: 9V - 24V AC or DC from wall wart (do not exceed 26VAC input)
- sensors used: MCP9700 linear active thermistors

I rate the output section of this circuit board for 24V, AC or DC, and it can handle 5 amps. Note that this is a thermostat and not a motor controller, to turn on or off motors that run on AC line voltages you should use a proper relay or contactor, and control that with this thermostat.

I include two temperature sensors with this item. They are linear active temperature sensors that have been cased and potted, with short pieces of wire attached so you can extend them for your project.

NOTE: This is designed to run off of most any power supply, and run any relay you have on hand. However, note the optional extras when you check out, for $10 more I will include a 25A Solid State Relay and a 12V 2A plug in power supply.


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