DIY coolbot mini heater

[aeviaanah]

I'm in the process of building my own coolbot to control walk in cooler AC unit. I need a heater that tricks the AC thermometer into thinking the room is warm. I see some guys using light bulbs but Id like to use something smaller and more professional, something like the heaters in 3d printers. I imagine these get way hotter than I need. Do they make these to where they get to around 70-100 degrees or so?

 

[zipster222]

My electrical engineer brother solved this problem for me a couple of years ago. With a quick calculation using ohm's law, he handed me a resistor and said to hook it up to a 12volt power source (from some scrapped household appliance) to give about a half watt of heat. I wrapped the resistor with the AC probe in a little bit of insulation. Has worked great for years.
Hope this helps.

 

[Bobby_M]

You're talking about a cartridge heater but they are usually much higher wattage than you need. Just use a resistor at a value that will make about 1 watt of heat. That's going to depend a lot on what voltage source you're planning to use.

 

[aeviaanah]

So simply Ohms law to solve for around 1 watt? Rather than stressing to get as close to 1 watt with parts laying around, is there an acceptable watt range here?

 

[zipster222]

Most important are the parts that you happen to have around. The more watts the more energy you will consume over time. Half watt seems to work fine. Less might also work. More than 10 watts seems like a waste of power.

 

[aeviaanah]

Built the heater using a 12v charger and a 100ohm resistor. Works great. thanks all