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I am working on a project where several 12V relays need to be controlled by the same push-button switch, essentially running the relays in parallel. I wondering whether relays configured in this way can work with a single flyback diodes. Multiple flyback diodes would essentially be diodes in parallel, and I'm not sure if this would provide any benefit. Can anyone advise?

Here is the normal schematic I'd use for a single relay: enter image description here

Here is the schematic showing how multiple relays would be configured in parallel. I'm thinking of controlling up to 5 relays in this manner:

enter image description here

Do I need multiple flyback diodes or can I get away with just one? What is the theory behind this and how do I tell what is necessary?

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    \$\begingroup\$ 1 is sufficient ..... just as 1 switch is sufficient, but you want to minimize your coil wire loop area in any/ all cases with twisted pairs \$\endgroup\$ Aug 13, 2021 at 15:24

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1 is sufficient ..... just as 1 switch is sufficient, but you want to minimize your coil wire loop area in any/ all cases with twisted pairs.

The benefit is the current from the switch continues in the same loop if switch to gnd and diode to Vcc is much shorter than the junction to all the relay coils. Otherwise, there may be a high dI/dt interference radiated from the change in paths.

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