0
\$\begingroup\$

I am modifying a mini cooler/heater and there is one component whose role I don't understand. The Peltier cell is attached to a heat sink on one side and is in contact with a metallic block on the other side. On top of this metallic block there is a black plastic cylinder with two incoming wires. The two wires are set at 0 V both when cooling and when heating. What does this unknown component do? Thank you.

components of mini cooler/heater

\$\endgroup\$
  • 1
    \$\begingroup\$ You're sure it's not a temperature sensor of some kind? \$\endgroup\$ – The Photon Feb 22 '17 at 20:02
  • \$\begingroup\$ I've now measured more carefully the voltages. The voltage at the end of the two cables is 0V when cooling. When heating, the voltage starts at 0.1V and then decreases over time. The component is connected to the ground with one wire, the other wire is disconnected from the rest of the circuit while cooling and is in series with a LED when heating. \$\endgroup\$ – Andrea Feb 22 '17 at 20:16
2
\$\begingroup\$

My guess is that the device is a thermal limit switch. The device opens the circuit up once a temperature level has been reached. The main purpose of it is to ensure safety and prevent a possible fire. The photo below is a thermal limit switch commonly found in your furnace

enter image description here

\$\endgroup\$
  • \$\begingroup\$ Thank you so much. Do you think that I should now re-apply some thermal paste to the Peltier given that I've separated it from the metal block for a few minutes, or would the one that was there be enough? \$\endgroup\$ – Andrea Feb 22 '17 at 20:27
  • \$\begingroup\$ If you have everything to put it back the way it was I would. After all safety first \$\endgroup\$ – Kvegaoro Feb 22 '17 at 20:29
1
\$\begingroup\$

What you are looking at is a temperature switch like this.

enter image description here

\$\endgroup\$
0
\$\begingroup\$

More likely it's a thermistor, a resistor that changes resistance with temperature. That's why you are seeing the voltage change. So if the voltage is decreasing when heating, the resistance is RISING with temperature, so it is a PTC (Positive Temperature Coefficient of resistance) thermistor. You said it was feeding an LED, so likely the other side of that LED circuit was powered when heating, so the resistance dropped between the LED and ground as it reaches it's design temperature and the LED gets less voltage and thus goes dimmer as it heats.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.