In previous blog ThermoPID Blog #1 - Introduction and Overview - Experimenting with Thermal Switches I have covered about high-level implementation plan for the temperature based PID controlled cooling system using thermal switch. This blog gives an idea about application of switches for heating systems and the aim is to try workaround these sensory switches and understand about the interfacing, toggling and recovery.
So to evaluate this system, I am connecting 3 of the thermal switches OHD1-30B, OHD1-50B and M-TRS5-60B specifically because their toggling limits are relatively lower and can be tested easily. Same would go for final DC-DC converter system as we need toggling at around 50 to 60 degrees celsius. Wiring up the circuit on breadboard, here is how it looks:
The sensors are serially connected with an LED and series resistor of 2K ohm. These switches are of Normally Closed(NC) type and all the 3 LEDs (Red, Green, Blue) glow altogether. The blue one in the above image isn't glowing because the temperature here at Bengaluru is just around that threshold(~30 degrees C). On cooling it a bit, the blue one glows too.
Here's a short video on toggling the 30 degrees C threshold OHD1-30B sensor by hand touch.
What's needed to observe is the toggling of each sensor as the temperature sensed by them increases. So for that matter, I used this electric kettle/ water heater and stuck 3 of those to the external metallic body of the pot. Not a good contact for the cylindrical M-TRS5-60B sensor, but turns out they toggle quite well and there's hysteresis while it needs to come back to the state. I am thinking of measuring the extent/ value of that hysteresis probably by plotting the temperature datapoints with trigger point. Any suggestions on this would be of great help to evaluate these switches on this setup.
Thanks for reading through. The next plan is to use the system with similar test case but using batter thermally conducting attachment with the DC-DC converter module. This will help in deciding thresholds and trigger points to active cooling and then applying the same using Arduino nano running a cooling fan.