This is a circuit found abroad. Use two Darlington tubes to control a coil. Let's talk about two diodes D1 (surge protection tr3). What is the function of D2?
Oriana ポストする November 27, 2020
D1 and D2 protect TR1 and TR3. When TR1 and TR3 are cut off, the relay discharges through D1 and D2.
Charisma ポストする November 27, 2020
Personal opinion: D1, it can be seen, but generally it is not directly led back to the positive end of the power supply, and D2 cannot see how it plays a protective role.
Gene ポストする November 27, 2020
Two diodes are equivalent to one diode connected between 4A and 4B.
