Hard wiring laptop charger circuit with ignition?

[philj]

Certainly never been too good at electronics.

I need to hard wire a laptop charger to come on via the ignition, so this needs to go through a relay. 4 pin I assume... Power, earth, ignition live, and power out?

Now where I'm lost is the specs...

Its going between the 12-19v converter, so 12v obviously. But how many amps?

What should the coil resistance be? And coil nominal current?

What size fuse? Just to be sure... should it be wired between the battery and relay, or relay and converter?

Also needs to have an off over ride switch, does that go before or after fuse?

[johne]

Certainly never been too good at electronics.

I need to hard wire a laptop charger to come on via the ignition, so this needs to go through a relay. 4 pin I assume... Power, earth, ignition live, and power out?

Now where I'm lost is the specs...

Its going between the 12-19v converter, so 12v obviously. But how many amps?

10 amps or higher. The 30 amp 12 volt relay from Maplin would do just fine.

What should the coil resistance be? And coil nominal current?

Doesn't matter in this application, whatever the particular relay uses.

What size fuse? Just to be sure... should it be wired between the battery and relay, or relay and converter?

10 amps. Ideally between battery and relay but relay and converter would do.

Also needs to have an off over ride switch, does that go before or after
fuse?

After - so the fuse is protecting everything after it from any faults/wiring problems.

Hope that helps,

John

[philj]

Lovely thanks.