12V thermostat relay controllers for your tent fan heater

Introduction

a 12V thermostat relay controller is a useful addition if you are using a 12V car demister fan for heating your hiking tent (obviously ensure the heater will not contact flammable material and set the tent on fire!) as it can automatically turn the heater on and off depending on its thermometer reading

these are the most readily available online controllers and are very inexpensive at around $10-20
have a plug in thermometer
can do 12V DC or 220V AC - both max. 20A (car demisters that run off cigarette lighter power are limited to 10A so will not be an issue)
it will re-use previous settings next time it is turned on
you do need to hard wire a power input cable (eg. from a male 12V cig lighter) and also the cables to output (eg. a female 12V cig lighter)

holding down the SET button for a few seconds will open up the P settings
short presses of SET button will take you to the next P setting
up and down arrows will change the value for the selected P setting then wait for blinking to stop and value will be set
see https://www.youtube.com/watch?v=64YBz_F-MKA

0: H = turns on/off a heater; C = turns on/off a fan
1: temperature difference from set temperature target to initiate on/off pending P0- usually set this to at least 1degC to minimise excessive cycling
- eg. for P0=C, and target set to 32deg and P1 set to 2deg, the fan will turn on when temperature hits 34deg and turn off when it falls to the target of 32deg
- eg. for P0=H, and target set to 20deg and P1 set to 2deg, the heater will turn on when temperature falls below 18deg and turn off when it rises to the target of 20deg
2: maximum temperature - if goes above this it will turn off
3: minimum temperature - if goes below this it will turn off
4: thermometer correction value - allows you to correct the thermometer reading Default = 0degC
5: the all important delay start in minutes - set this to a reasonable delay to avoid excessive cycling and adds to the P1 behaviour
6: is the alarm temperature which will turn off the device if temp is reached (this can be disabled by setting it to OFF by going above 120deg when setting the value)
7: allows locking the temperature/value change buttons
8: factory reset (this can also be down by holding both up and down arrows for a few seconds)

WHO recommends sleeping air temperatures should be above 18degC when possible
Target temperature 20degC (can set to lower than this to reduce power consumption and accept lower air temperatures)
P0 = H
P1 = 2 degC
P2 can be anything above your target temp
P3 can be anything below target temp - P1 setting but probably just set it to 0 degC
P4 can be adjusted if you think thermometer is not reading accurately
P5 could be set to 0 or perhaps 1 if you want to further reduce cycling of on/off