I am having trouble identifying the following component: unkown component

It is in circuit as follows:


simulate this circuit – Schematic created using CircuitLab

From the circuit I would have expected it to be a pulldown resistor style to indicate that the connector is plugged in. The other pins of the connector are a wind sensor pulse output.

Any help is greatly apreciated, Thanks

Update : After the helpful insight about checking it to be a PTC of NTC thermister I performed measurements and it was 22kOhms. Held it with my fingers and it decreased to 20k and breathing on it I managed to get it to go down to 18k.

In circuit measurements with the Vcc = 5V, across the thermistor it was 1.4 V approx.

So It is an NTC resistor

And it makes sense that it be an NTC resistor because when the weather is too cold, the wind sensor could freeze up and you would not know if the measurement is valid. The resistance would go up and therefore the voltage and that would be tending to a similar scenario as if the sensor was disconnected. i.e. Open circuit.

  • 1
    \$\begingroup\$ Connect an ohm meter in both ends and then warm the part with your hand (you could place it in the freezer in advance for biggest effect) while observing the resistance. Then you'll see 1) if it is a thermistor and 2) if so whether it is PTC or NTC. \$\endgroup\$
    – Lundin
    May 20 at 9:32
  • \$\begingroup\$ NTC would make hardly any sense in the shown circuit, unless it is meant to detect freezing \$\endgroup\$
    – tobalt
    May 20 at 9:42
  • \$\begingroup\$ @tobalt Why not? This exact schematic could be taken from your average Li/Ion battery charger. They all use NTC for some reason. \$\endgroup\$
    – Lundin
    May 20 at 13:16
  • \$\begingroup\$ @Lundin, because the MCU signal will be already low at room temperature. If the device overheats, it will be just drawn more low. \$\endgroup\$
    – tobalt
    May 20 at 13:21
  • \$\begingroup\$ @tobalt And that's exactly how battery chargers work, shutting off when they detect an unexpected rise in current, so...? \$\endgroup\$
    – Lundin
    May 20 at 13:26

That is probably a type of a thermistor (NTC or PTC). Their resistance changes with temperature. 22K would be the resistance at room temperature (25°C). Perhaps more info about the device would help with identifying the part, but I would suggest you trying to warm up / cool down the part and measure its resistance with your multimeter.

If it changes significantly, then it is probably a thermistor. There are usually two types of thermistors: Negative and Positive temperature coefficient. NTC thermistor's resistance lowers with higher temperature, PTC vise versa. More about thermistors here.

  • \$\begingroup\$ aha, thankyou for the insight, I will try to perform some measurements this afternoon/evening. That would make sense acting as a double function. 1. to know if the connector is connected and 2. it would indicate that when freezing temperatures are present the wind sensor input should not be considered valid. \$\endgroup\$ May 20 at 9:31
  • \$\begingroup\$ Yes, that would make sense. They are usually not super precise (± a few degrees), but for detecting, if it is freezing, they are alright. \$\endgroup\$ May 20 at 9:45
  • 1
    \$\begingroup\$ Did the measurements and it was indeed an NTC with what I'm guessing would be nominal resistance of 22k@25ºC \$\endgroup\$ May 20 at 19:29

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.