[![enter image description here]]
This is a new photo :
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.Sign up to join this community
No, DB3 is not a diode. It is a diac, a non-directional semiconductor switch that can be turned on when its breakover voltage is exceeded.
Breakover voltage of DB3 is 28V. Your unregulated power supply voltage could touch 34V. The DB3 would get triggered and short circuit the power supply, thereby damaging itself and/or the power supply in the process.
A 1N4001 would suffice as a freewheeling diode for this application.
You don't need a snubber diode.
Figure 1. The bridge rectifier acts as a snubber for the relay.
When the AC switches off the relay current will continue to circulate through the diodes of the bridge rectifier.
Since you have clarified that there is a switch in the circuit but haven't given any details on it we can only suggest this circuit.
Figure 2. As @MarcusMüller has suggested, placing the switch in the AC side solves the problem.
Breakdown voltage 28V minimum Repetitive current limit: 2A,
Also its a back to back device, so there is no forward voltage, I would say this is a poor choice for a relay unless you needed the relay to close very quickly. if your supply voltage gets a little too high, or your circuit re-powers the relay before the breakdown has recovered, it will short out the supply to the relay may destroy itself from the excess amount of current flowing through it,
Avoid if at all possible for this application.