Osiris

Thomas thank you for your reply. I changed the 1N4148 diodes for 1N4007(1000V/1A). I do have a ground plane and al ICs are decoupled. The transistor 2N3904 can switch 54mA with 3.3 volt from the Teensy and a 10K resistor : Ib = 3.3V - Ube(0.6V)...

Hello, I designed a PCB with a Teensy 4.1 and 2 miniature PCB relays type TQ2-12V. The relays are switched on by a NPN-transitor. The protection is a fly-back diode (1N4148) across the coil and a TVS-diode (SAC12) nearby across the 12VDC power...