Hello,

I was taking some pieces of an old PCB I had (not mine) and I saw in the power line a component that I didnt know what it was so I post here for you to help me out clear my curiosity:
- The PCB input is marked 24V
- The PCB has regulators of 9V and 5V
- The component I dont know what it is looks exactly like a varistor
- The component is placed on the input power line (VCC)
- I think that is has to be some kind of filter or similar


In the schematic I draw a varistor to represent the component I dont know as far as it looks like that. I understand the diode and capacitor purpose

Thank you for reading

 

Post a picture of the component.

 

A thermistor?

 

A thermistor?

I check on google because I have never used a thermistor t does look like a thermistor. And for what I have just read in google it should be a PTC thermistor to protect against overcurrents when temperature rises?

Thank you, I can always learn something new in this forum

 

As it is on the power input it is more likely to be an NTC to limit inrush current. When first switched on it would have a high resistance and so limit the current but then the current heats it up and allows the full voltage through to the circuit.

 

As it is on the power input it is more likely to be an NTC to limit inrush current. When first switched on it would have a high resistance and so limit the current but then the current heats it up and allows the full voltage through to the circuit.

I understand what you mean, but for what I read if the thermistor is in series with the power line (as I drew) it would be an PTC thermistor protecting against overcurrent condition? Please correct me if I am wrong, I reading this in Wikipedia (not the most trustfull source)

Thank you

 

It could be either. We don't even know for certain that it is a thermistor.