Review on 🌡️ HiLetgo 2pcs W1209 12V DC Digital Temperature Controller Board Micro Digital Thermostat -50-110°C Electronic Temp Control Module Switch with 10A Relay and Waterproof by Chris Goldsby

I bought this product for a small side project. I wanted to add a 12 volt fan to cool the charging transformer in the backup battery when charging from the grid, but I didn't want the fan running 24/7. The UPS no longer charges small 7Ah 12V batteries, instead charging two 90Ah 12V batteries. Installing the unit in the UPS cabinet was fairly easy, but wiring and setup was another challenge, as this product is delivered without documentation. Note that this device only works in degrees Celsius. If you want to know the temperature in Fahrenheit, you need to convert it. Luckily some of the other reviews have links to instructions and schematics. in my case) do the following: 1. Connect a 12V power supply to the +12V2 terminal. Put a short jumper from the +12V terminal to the K1 terminal, tighten the +12V and K1.3 terminals. For a 12V device (a fan in my case) connect the positive power line to terminal K0 and tighten terminal 4. For a 12V device (a fan in my case) connect the negative return to the GND terminal. Also connect the negative return from the main power supply to the GND terminal. Tighten the clamp. To program the unit to run the **cooling fan** like I did, do the following: 1. Press the SET button once and set the desired "off" temperature with using the "+" or "-" keys. This is the temperature at which your fan will turn off. After you have selected the "Off" temperature, press the "SET" button again. This should help you. If you set the temperature to 30°C, the default fluctuation temperature is 2°C. This means that the temperature sensor must reach 32°C before the fan will turn on. The fan runs until the temperature of the thermal sensor drops to 30°C and then turns off. If you want to change the default swing temperature of 2°C, follow these steps: 1. Press and hold the SET button until P0 appears on the screen. Press the + button until P1 is displayed. Briefly press the "SET" button to change this value. You should see "2" which is the current default. Press "+" or "-" until the desired temperature is reached, then short press the "SET" button again to set the new value. then the temperature sensor must reach 40°C before the fan turns on. The fan will then run until the temperature sensor reaches 30°C, after which it will turn off.