I'm working on an automotive project. I have an electric water pump and fan, both of which will be powered through relays. I also have an on-off-on dpdt switch. What I'd like to achieve is activating the pump at both poles and just the fan at the other. This seems doable, but in all my attempts I've only been able to have both on or both off. How do I wire the switch to achieve my goal?
This was what I had in mind for EMI control of Pump glitches which are probably worse than relay coil glitches.
- no transistor protection needed if battery nearby.
- Battery cables are twisted as well for EMI control.
Avoid large current loop area with paired wires or twisted wires
Although it may not matter in your application but for cars , they have to survive reverse jump cables and 2xVbat jump cables so reverse diodes are verbotten as they would blow. So, they use Snubber power resistors, often inbuilt.