Temperature Sensor Clamp for Homemade Lab Incubator

thingiverse

My grand 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. I was looking at various boxes and heaters to use and stumbled across the Hot Logic Mini Personal Portable Oven for $45 at various online outlets. It’s a small, insulated, box-like, zippered, soft container with a 110 volt hot plate that is just powerful enough to heat a lunch or dinner in a few hours. I then found a simple on/off temperature regulator/thermostat (WILLHI WH1436A - available online for $30) that is close to perfect for this application. It’s not a PID controller but lets you set 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 come up with a simple clamp to hold the temperature sensor in contact with the hot plate. I have no association with either company. The oven and controller just work well together and made for a nice bit of cheap lab equipment for my niece with just a simple 3D-printed clamp. The result is a pretty slick incubator that’s compact and relatively inexpensive. The temperature sensor just slides into the hole almost to the end and the clamp pressure holds it in contact with the hot plate and in position. For incubation duties the temperatures will never be high enough to cause problems for the plastic clamp but obviously higher temperatures could be a problem. For this application, though, it works great. 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 empty seems to be a few degrees above the setpoint since it heats quickly and cools slowly. More thermal mass would help but for incubating simple biological samples that is apparently tight enough. I think a diode in the hot plate power cord would slow the heating and probably tighten the range even more. A PID controller would also help and those aren’t too much more expensive.