I’m planning a little trickery with the wiring.

Obviously to be legal the (what will be 6) LED’s on the front bar need to be through a relay to only switch on with the main beam.

I want the side and rear LED’s on ahand break cut out relay so that theywill only work when the hand break ison (therefore unable to be on whilst driving on the road).

HOWEVER I am also planning to havean override switch for the above for when I’m off road. This will most likelybe a key switch so that it can’t be accidentally turned on whilst on road(and by a difficult MOT tester andargue that it is not road legal....

This is my plan for the front bar relays;



All the switching will be done on the common -ve so I maintain independentswitching on the 3 pairs of LED’s on the bar. This will basically disconnect the -ve unless the main beam is on. The override relay will switch the triggerfrom the main beam to a permanent +ve therefore being able to have them on regardless of the main beam state.

The problem I have is working out the hand break cut off. Again, switching willbe done on the -ve side to retainindependent control of left/rear/rightpairs.

The problem I have with this part is that the head light trigger is 0v until the main beam is on when it goes 12v. Thatis easy to trigger a relay. However thehand break is effectively 12v when thehand break is OFF and 0v when ON. This is basically backwards to what Ineed to trigger a relay.... I’ve considdered a normally closed relay but as I don’t routinely use thehandbreak (it’s an auto so I just leave it in park, the American way) then thatwould mean that the relay is isenergised most of the time which I don’t want.....

Is there a somewhere I could pick upasimple 12v when the ‘box is in Park?

could just mount a switch that is tripped when you put it in park

I simply cannot see the point in wiring them up to the hand brake.

Seems an unnecessary complication and when you are already planning on putting them on a locked isolation switch it seems even more pointless.

You could use a DPDT switch to select between full beam/off/on and be done with it?

edited to add

If you are desperate to engage them only when in P then you would easily mount a micro switch under the console that would trigger the relay?

LED’s plus a relay... why? Sorry I couldn’t be interest to read any more, as I don’t see as it got to do with a disco 2 or any other disco

Spot1 said:

However thehand break is effectively 12v when thehand break is OFF and 0v when ON. This is basically backwards to what Ineed to trigger a relay..

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Why?... you can trigger the relay with earth while the other side of the coil is live

Or use a normally closed (or switchover) relay.

But like others this seems like overkill to me.

Why do you want BREAK the BRAKE lights!

sierrafery said:

Why?... you can trigger the relay with earth while the other side of the coil is live

Click to expand...

This is the kind of thing I was looking for! Thank you. I’m not sure why I didn’t see it as an option....

Interceptorxj said:

Why do you want BREAK the BRAKE lights!

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I’m not touching the break lights.... I just want a “safety” cut-out so that I can’t accidentally drive down the road with say bright white flood light LED’s blinding other road users.

discool said:

LED’s plus a relay... why? Sorry I couldn’t be interest to read any more, as I don’t see as it got to do with a disco 2 or any other disco

Click to expand...

I’m not adding relays for the reason of high current switching as is the case with halogen floods for example. I’m using them as “automatic switches” to switch on/off relative to something else such as the LED’s on the front only switching on when main beam is on which is a legal requirement for road use... if I just tapped into the wire to the headlights then I’d most likely overload that circuit and keep blowing fuses or just set my truck on fire....