Temperature Sensor Clamp for Homemade Lab Incubator

thingiverse

My niece needed a temperature-controlled little incubator for science projects, but most are too big and too expensive. The small ones seem to be designed for eggs, so I looked at various boxes and heaters to use instead. That's when I stumbled upon the Hot Logic Mini Personal Portable Oven for $45 at several online outlets. It's a compact, insulated box with a 110 volt hot plate that can heat up a meal in just a few hours. I then found a simple on/off temperature regulator/thermostat (WILLHI WH1436A) available online for $30, which works perfectly for this application. It allows you to set precise on and off setpoints within 0.1 degree F, and the hot plate power draw is just a fraction of its capacity. The only thing I needed to do was create a simple clamp to hold the temperature sensor in contact with the hot plate. Fortunately, it's not too complicated and can be easily designed using a 3D printer. I have no affiliation with either company, but the oven and controller work amazingly well together, making for some great lab equipment at an affordable price. The result is a sleek incubator that's compact and relatively inexpensive. For incubation duties, the temperatures will never be high enough to cause problems for the plastic clamp, but higher temperatures could potentially be a problem. However, in this application, it works wonderfully without any issues. I'm not using any thermal compound, and the regulation still ends up with about a 10 degree F temperature cycle range with an empty incubator. The average temperature seems to be a few degrees above the setpoint since it heats quickly and cools slowly. Adding more thermal mass would certainly help, but for incubating simple biological samples, this setup is apparently sufficient. I think adding a diode in the hot plate power cord would slow down the heating process and probably tighten the range even further. A PID controller would also be beneficial and isn't too expensive.