DIY termostat for Solar Air Heater

[alf_9]

Hi there!

I am trying to build DIY termostat powered by 12V battery for Solar Air Heater. I am currently located in Afghanistan where access to electrical equipment is not so easy, but I know that lots of workshops are able to offer basic elements like resistors, capacitors etc.

I will use 12V computer fan, 12V battery (no access to grid).

Any advice where I can find DIY instructions to make simplest termostat?

[inetdog]

Hi there!

I am trying to build DIY termostat powered by 12V battery for Solar Air Heater. I am currently located in Afghanistan where access to electrical equipment is not so easy, but I know that lots of workshops are able to offer basic elements like resistors, capacitors etc.

I will use 12V computer fan, 12V battery (no access to grid).

Any advice where I can find DIY instructions to make simplest termostat?

The simplest thermostat is composed of a bimetal strip (two types of metal bonded together to form a thin strip). The different rate of expansion of the two metals makes the strip bend in one direction of the other as it gets hotter or cooler. That motion is used to open or close a switch contact. That contact can be mechanical, a mercury switch, or movable magnet that opens and closes a reed relay contacts sealed in glass and operated by an external magnetic field.)

It would not be easy to make your own bimetal strip, although you could do so. Better would be to get a surplus thermostat used for any other kind of heater and adapt it to control your fan.

[alf_9]

The simplest thermostat is composed of a bimetal strip (two types of metal bonded together to form a thin strip). The different rate of expansion of the two metals makes the strip bend in one direction of the other as it gets hotter or cooler. That motion is used to open or close a switch contact. That contact can be mechanical, a mercury switch, or movable magnet that opens and closes a reed relay contacts sealed in glass and operated by an external magnetic field.)

It would not be easy to make your own bimetal strip, although you could do so. Better would be to get a surplus thermostat used for any other kind of heater and adapt it to control your fan.

Hi inetdog

Thank you for advice. I will check surplus thermostat. I think that kind of thermostat is common use in hot water boiler here in Kabul. Is it possible to adjust that kind of thermostat? Or on/off temp. is fixed and I need to get specific temp switch - thermostat (switch on +20C / switch off +15C)

[inetdog]

Hi inetdog

Thank you for advice. I will check surplus thermostat. I think that kind of thermostat is common use in hot water boiler here in Kabul. Is it possible to adjust that kind of thermostat? Or on/off temp. is fixed and I need to get specific temp switch - thermostat (switch on +20C / switch off +15C)

Many water tank thermostats (for electric heating) are adjustable. But the normal adjustment range is typically from a low of ~120F to a high of ~180F, which will do you no good. But if you have a way to calibrate the results you can often modify them (bend them or turn the adjusting screw farther than it was meant to turn) to cover a different range.
The limit thermostats used for safety, on the other hand, are deliberately made not to be adjustable.
A thermostat made for a portable electric room heater would be closer to what you need. Or just a normal thermostat for a forced air heating system or an air conditioning system.
Do not try to use a "millivolt" thermostat which is powered only by a thermocouple in the pilot light though. The contacts cannot handle either the current or voltage that you will need to operate a relay or valve.

[semenov_v]

Hi,
You may buy termostat on aliexpress.
It cost about 1$ for 12V termostat.