Device

The environmental testing laboratory that I worked at used a Thermo Fisher Scientific Model 815 incubator in their biology department. It is actually a modified Frigidaire TFFU2065FW0 refrigerator, which keeps the compressor running non-stop while simultaneously controlling what was originally the defrost heating element to counteract the cooling, maintaining a stable temperature of 20° C or 68 ° F (a standard for "room temperature").

Electrical issues

The incubator in question was something of a lemon due to its electronics. It would behave erratically, sometimes refusing to "boot" (nothing visible on the interface, no relays clicking on). It was quite elusive, as the power supply looked stable, nothing visibly damaged, but somehow the microcontroller would end up killed and we'd either have to replace the chip (it was socketed), or we'd have to replace the entire CPU board.

We never had confidence in how long the incubator would stay up and running, and if it broke down during processing mold samples, it would ruin the customer's data which is very costly. After several rounds of replacing the same parts, I decided to replace the entire electronics rather than waste any more time on these flawed ones.

Original electronics

incubator original electronics

Replacement electronics

In the interest of rapid prototyping, and due to their simplicity, the replacement motherboards were designed to be single-sided and were acid etched in-house. (This is why they are so bare looking on their top sides).

The new boards are very simple compared with the originals, taking advantage of modern microcontrollers being much more integrated. They are more reliable, easier to debug, and has more expandability being WiFi connected. Both firmware updating and temperature regulation PID tuning can be performed remotely without physical access to the machine.

incubator replacement electronics

Links:

Precision™ Low Temperature BOD Refrigerated Incubator -- Thermo Fischer Scientific (on the Internet Archive)