Assuming a low-power signal relay, 3V, 140mW coil, driven by a 2N3904 NPN transistor, do I need a flyback diode? If necessary, what parameters determine it?
Rainy ポストする January 29, 2021
Have you ever used LTspice? I tried it without a diode and the peak value is 11kV.
Tino ポストする January 29, 2021
What should be considered is the energy that will damage the transistor, similar to an electrostatic pulse.
Doyle ポストする January 29, 2021
The flyback diode is selected according to the voltage and current. For example, your coil voltage is 3V and the power is 140mW, so the current=0.14/3=0.046A, then you can choose the diode, you can choose 1N4007, because this is very cheap Of it.
