I have made a relay controller module which switches a automotive relay when a ULN2003A sinks current on the separate main board. The module is in an always active state, but the requirements have changed for its functionality, it now has to handle with multiple switching cycles instead of a once off cycle. The only constraint is that it has to have three wires only: signal, GND and relay.
The circuit is this below:
Vbatt = 12-13V from car battery
I know there are a few questions on EE.SE on the methods of flyback diodes, but I can't decide which method I should be using, I thought of using a zener, but I am unsure of that method. There is also a current reducing circuit after the NPN transistor, consisting of a resistor and capacitor in parallel Also the two answers below seem to contradict to a point.
I thus need assistance in the method in which to provide protection to the module, components within the dashed line.