How to provide a filtered noiseless 12V supply?

[andyborris]

As the title says really, I need to have a interference free ignition switched 12V supply in my Landy.

Will taking a 12V feed from the from the Lucas ignition switch be OK, or should I do this by using a relay? I.E. Ignition switch controls relay, relay switches direct from battery? Or will the relay coil make "noise"?

The Landy has little in the way of electronics, gauges have stepper motors and the rest is 1960's electrics!

[colnerov]

One likely source of 'noise' is from the alternator, the internal rectifier may be inefficient. Try disconnecting it to see. Try a standalone battery. FFR (fitted for radio) military Land Rovers had all sorts of kit on them for noise suppression even down to screened HT leads. Lots for you to think about...GO.

[andyborris]

Thanks.

I only need one 12V "clean" supply to power an ECU.

Could the alternator put a lot of "noise" into the rest of the car, it only charges the battery and on the Landy, it's wired direct to the battery with a 175 amp cable? I can also route the wiring for this ECU well away from the alternator and it's wiring.

Was thinking about those filters that you can buy for aftermarket reversing cameras, stop the canbus reversing lights messing up the image. Wonder if they'll provide a "clean" supply?

Just want to make sure that any problems I get with ECU, won't be electrickary ones!

[squonk]

The reversing camera filters won't be capable of providing the current requirements for the ECU. An ECU will can pull 10+ Amps.

Does the alternator have a supressor terminal? Usually a small spade terminal marked D+. If it does just fit an alternator supressor.

[andyborris]

After re-reading the installation instructions, I think providing I keep the wiring away from the plug leads and charging circuit, it'll be OK. Might need a EMF shield for the wiper motor because the ECU will be close to it, but for now I'll just twist the motor wires.

However, the weird rabbit hole that's linked to EMF shielding is a bit frightening! Sleeping under £700 EMF shielding sheets...wtf!

[dodgerover]

[Source] andyborris said:

However, the weird rabbit hole that's linked to EMF shielding is a bit frightening! Sleeping under £700 EMF shielding sheets...wtf!

Probably a good idea if you have an older pacemaker or one of the ones which you can't weld when it's fitted and you are worried about another Carrington event.