Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Normal
I suppose a PWM control of each transistor (as opposed to on/off) could be used to precisely control the resulting heating power, but a PTC resistor is supposed to self-regulate to a constant temperature? Another clue is the lack of current feedback therefore I think the heating power is simply controlled by switching on/off a combination of the three resistors .Without an oscilloscope a crude way to check is to set the multimeter to AC and measure the three control lines again.A quick way to test the resistors is to bypass the transistors altogether, the measured voltage * current should give you the resulting heater power...
I suppose a PWM control of each transistor (as opposed to on/off) could be used to precisely control the resulting heating power, but a PTC resistor is supposed to self-regulate to a constant temperature? Another clue is the lack of current feedback therefore I think the heating power is simply controlled by switching on/off a combination of the three resistors .
Without an oscilloscope a crude way to check is to set the multimeter to AC and measure the three control lines again.
A quick way to test the resistors is to bypass the transistors altogether, the measured voltage * current should give you the resulting heater power...
