How to set a XH-W3001 thermostat module, and a look inside.

A quick look at the programming and circuitry of a common and very simple Chinese thermostat module. The module is designed for 12V but is apparently available in other voltage variants. The output is switched 12V on this unit and has the matching negative wire to drive a load directly.
The module can control heating or cooling by the use of a start temperature and a stop temperature.
To set a temperature press and hold one of the buttons until the display starts flashing. The left button is for the ON temperature and the right button is for the OFF temperature. While the display is flashing that temperature can be adjusted up and down in small 0.1 degree steps or faster if the up/down button is held in continuously. When the temperature has been set the display will stop flashing after a short delay and revert to displaying the current sensed temperature.
Hysteresis (temperature difference between turning on and off) is simply set by choosing that gap between the on and off settings. So an ON temperature of 20C and an OFF temperature of 23C would have a hysteresis of 3C.
The relay is apparently rated for 10A, but will be more reliable if used at much lower current. The switched output can drive an external relay or small load directly.
Pressing and holding both buttons will do a short display test and revert to factory set temperatures.
Any temperature setting changes are stored in nonvolatile memory and will be kept even if the unit is powered down.
The module uses a common 10K NTC thermistor.

Here's a general eBay search link for this unit:-
http://www.ebay.com/sch/i.html?_from=...

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