Camera wiring problem.

[RoyC]

I am trying to install a camera through my ignition switch.
Problem is, my bike is pos earth and the camera is neg earth.
How can I wire it to come on when the ignition is turned on ?
I know that I could wire it separately with its own switch but I would rather have the ignition fire it up.

[BSA_54A10]

Use a relay.
A standard relay can either have the + side or - side or both sides of the trigger circuit being used to turn the relay on.

[Triton Thrasher]

Does the camera have + and - power leads?  Likely red and black, respectively.

Connect the camera positive wire to a wire that goes to battery positive or to the bike frame.  The frame is usually less reliable.

Connect the camera negative wire to the switch terminal that becomes live when you switch the key on.

It seems highly unlikely that the camera has a metal casing or clamp meant to form part of the return path.  That would mean you having to insulate it from the bike frame.  Can you post a picture of the camera or the instructions?

[RoyC]

Does the camera have + and - power leads?  Likely red and black, respectively.

Connect the camera positive wire to a wire that goes to battery positive or to the bike frame.  The frame is usually less reliable.

Connect the camera negative wire to the switch terminal that becomes live when you switch the key on.

It seems highly unlikely that the camera has a metal casing or clamp meant to form part of the return path.  That would mean you having to insulate it from the bike frame.  Can you post a picture of the camera or the instructions?

It has red wire with 2amp fuse and a black wire.
The live wire on the ignition switch is negative feed.

I have tried wiring - to + and it blew the fuse.

I am delighted with the cameras performance when wired up on the table.

This is the camera  -  https://www.ebay.co.uk/itm/1080P-HD-Motorcycle-Camera-Motorbike-140-Camcorder-Video-Recorde-Dual-Lens-Cam/113778169461?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

[RoyC]

Use a relay.
A standard relay can either have the + side or - side or both sides of the trigger circuit being used to turn the relay on.

It had crossed my mind to do something with a relay, but am not sure what relay to order or how to go about wiring it up.

[Triton Thrasher]

Why did you put - to +?

[RDfella]

“I have tried wiring - to + and it blew the fuse.”

-ve still goes to –ve  & +ve to +ve, it’s just that the machine’s earth is opposite to the camera’s earth, meaning that if the camera has any part which connects to its –ve side, then it will short and blow a fuse or destroy the camera.
I looked into this when fitting a modern radio into a classic +ve earth car. Clearly the radio’s frame would end up being live. It would need to be insulated from the car’s body but even that’s not enough, because the risk of short when anything touched it remains.
I had a wiring diagram how to overcome that, but can’t find it. Briefly the answer is to get a voltage stepper-upper from 12v to 24v. You then mount the radio (or other device) normally, but feed it 24v +ve. That has the effect of feeding it 12v neg earth.
Trouble was, I couldn’t find a stepper-upper (they’re dead cheap) which would work with +ve earth. They’d work fine –ve, but not +ve, when they would simply feed through the 12v without upping it to 24v. Guess the units had a common –ve rail inside them.

[RoyC]

What I need is something that will turn on a completely separate circuit.

I could have a manual switch but that's too easy and I would have to remember to turn it on every time.

[RoyC]

Why did you put - to +?

To see if I could connect the neg earth camera to the pos earth ignition switch.

I can't 

[Triton Thrasher]

Connect the camera power supply + to + on the bike.

Connect the camera power supply - to - on the bike.

If you want it to switch off with a key switch on the bike, connect the camera power supply -  to the switched side of the key switch on the bike.

If you’re worried about the camera casing being live (looks plastic to me),  test for continuity between the - on the camera power supply and any metal bits on the casing of the camera.  Any modern electric gimmicks I’ve bought have no electrical connection to their casing.  They have red wire and black wire, + and -.  That is the camera circuit.

[RoyC]

Connect the camera power supply + to + on the bike.

Connect the camera power supply - to - on the bike.

If you want it to switch off with a key switch on the bike, connect the camera power supply -  to the switched side of the key switch on the bike.

So I'm connecting the camera + supply to the bike earth and the cameras earth - to the bikes power.
Isn't that the same as when I connected + to - and blew the fuse ?

[Triton Thrasher]

Connect the camera power supply + to + on the bike.

Connect the camera power supply - to - on the bike.

If you want it to switch off with a key switch on the bike, connect the camera power supply -  to the switched side of the key switch on the bike.

So I'm connecting the camera + supply to the bike earth and the cameras earth - to the bikes power.
Isn't that the same as when I connected + to - and blew the fuse ?

Connecting + to - is not the same as connecting + to +.

The camera has + and-.
The bike has + and -. 
Connect + to + and connect - to -.

[RoyC]

Connect the camera power supply + to + on the bike.

Connect the camera power supply - to - on the bike.

If you want it to switch off with a key switch on the bike, connect the camera power supply -  to the switched side of the key switch on the bike.

So I'm connecting the camera + supply to the bike earth and the cameras earth - to the bikes power.
Isn't that the same as when I connected + to - and blew the fuse ?

Connecting + to - is not the same as connecting + to +.

The camera has + and-.
The bike has + and -. 
Connect + to + and connect - to -.

I'll give it a go when I can find a 2amp 20mm glass fuse.

[duTch]

 

...I have tried wiring - to + and it blew the fuse......

 I bought a Rear view camera and testing it before installing I accidentally did that and blew it up- because it was on 'special', I went back and bought two more (one for me and one fro the youngsta) Pulled the blown one apart and found a a chip inside (5mm x 4mm x1.5mm) with burn hole and bought 10 online for $3 and did micro-surgery (still have 9 spares ), still works a treat after about 4 years, but doesn't stop me reversing into trees 'n shet....

 First experience I had with reverse polarity was jury rigging a Pioneer stereo into my Ma's Austin1800 age 17, and likewise blew one channel chip- made me understand (half) stereo

 Just do as TT says I reckon.....

[RoyC]

 Just do as TT says I reckon.....

I'll do that as soon as my new fuses get here.