Help! Electrickery expert required

Wiring in my boot popper and I was wanting to use the handbrake switch to earth the popper switch. So far so good except I seem to be getting a parallel earth through the h/brake switch meaning the popper switch will be activate-able at all times, whether the handbrake is on or not. I'm guessing the handbrake switch is probably earthing back through the dash when voltage is applied from the popper switch.

To overcome this I'm thinking a diode added between the popper switch & the handbrake switch is required? If so, what specification of diode should I be looking at? The circuit has a 15 amp fuse fitted. I know nothing about working out what rating of diode I'd need other than 12v.

Thanks

I think I'd add a second switch.

However you could use a LED for your diode.

Good call on the LED. I'll try & give that a proper go tomorrow but a rough jury-rig suggests success.

Cheers

I guess what you are trying to do is use the handbrake as a safety device, so you cant "POP" the boot unless the handbrake is ON.

If I understand correctly your problem is when you connect to the handbrake switch, the popper still operates, even when the handbrake is OFF.

How have you got the wiring configured for the "popper"?

When the handbrake is OFF the feed to the handbrake switch is ON (12V), and when the handbrake is ON, the feed to the handbrake switch is OFF (0V) (The handbrake switch grounds one side of the brake warning lamp, making it illuminate).

See enclosed drawing (note the top drawing shows the way the handbrake switch works and is drawn with the handbrake ON)

Therefore your "popper" circuit must use the handbrake switch as a "Ground Path", so your circuit will be something like:-
12V to the popper switch.
Popper switch to popper device.
Popper device to handbrake switch

See enclosed drawing

The diode is optional, but note where it is positioned!
I would try without it first as should not be necessary.
I would also advise taking the 12V for the popper from an ignition feed, as if you take it from a permanent 12V then the diode will be required.

A schotkey diode is recommended, as a standard diode might cause the lamp to dim slightly.

The diode only needs to have a current rating of about 500mA to 1 Amp, as it only needs to pass enough current for the bulb.

Peter

Excellent, thanks. I have a 12v feed to the popper switch from the fuse box which then goes direct to the handbrake switch operating a relay for the popper solenoid. The diagram you provided is pretty much what I have in place, but on testing with a multimeter, without diode, it was still getting an earth whether the handbrake was on our not. An LED fitted in place temporarily seemed to cur it, just need to fit a diode now.

Wish I'd seen this diagram a week ago, would have potentially saved a lot of puzzling Nonetheless, glad I had it almost figured out by myself.

Thanks very much

Or replace the handbrake light bulb with an LED one?

That's an idea too, but one for further down the line. I'm going to have enough trouble getting the car back together for the weekend without pulling out the dash as well!

Feck!

:woo2:
All back together again apart from the seats which I still have to fit the heated pads to. Wiring diagram above worked a treat, got a diode from Maplins this morning for 54p and soldered it in line, popper button works a treat now but only when the handbrake is on.
Unfortunately the solenoid isn't working, think I might have damaged it when i was testing it, but no big deal, easily replaced.

Well pleased, got the heated rear window connected up too while I was at it, just need to get a screen now...