Contant 12v power source

[Lexus-IS]

Does anyone know if there is a constant 12v power source available anywhere in the drivers door or there abouts in the footwell etc? Need a 12v supply that is always on even when car is locked. Needs to be able to handle a few amps of load. 

[Texas]

"A few Amps even when car is locked"

Can't see your Battery lasting long if you draw a few amps without engine running?

prey tell??? pourqui?

paul m.

[Verbout]

As above, intrigued.

[Lexus-IS]

13 minutes ago, Texas said:

"A few Amps even when car is locked"

Can't see your battery lasting long if you draw a few amps without engine running?

prey tell??? pourqui?

paul m.

It won't be running always, I will use a relay so that when the mirror puddle light is on it will use that power source. It's to power LED DRL's  when the puddle lights go on.

[Texas]

I thought LED's were very low power, as regard current draw so it won't really be a few amps will it? are they rated with a current draw along with a supply voltage?

paul m.

[Lexus-IS]

To be honest I don't think it will be more than 1A and it wont be drawing power for that long only when the puddle lights under the door mirror is on. I was going to run it from the +12v from the puddle light bulb but it seems that the puddle light in the mirror doesnt share a common ground wire. So therefore I cannot just use the +12v from that. So what I have decided to do is power a relay with the + and - from the puddle mirror light and have a constant power source. So when the puddle light goes on then it let the always on power through.

[sorcerer]

I'm still intrigued.

You say it's to power LED DRLs but you also say "even when car is locked" - by which I'm assuming you mean parked up and locked, with the engine off, in which case you won't need DRLs???

[Lexus-IS]

The new Lexus models when you come up to the car even if you do not unlock it the DRL LED turns on. This is the feature I am trying to achieve. If the car is locked and you walk up to it, the mirror puddle lights turn on. The car at this point is still locked. So quite simply put I just want the front LED DRL to turn on.

[sorcerer]

10 minutes ago, Lexus-IS said:

The new Lexus models when you come up to the car even if you do not unlock it the DRL led turns on. This is the feature I am trying to achieve. If the car is locked and you walk up to it, the mirror puddle lights turn on. The car at this point is still locked. So quite simply put I just want the front LED DRL to turn on.

Ah right, fair enough.

So essentially you're going to provide power to the DRLs when they aren't meant to be powered up. Just be aware that cars that are wired from the factory to have the feature you want may have some electrical wizardry to stop power backfeeding into other circuits whereas yours won't have that.

[Lexus-IS]

Yes i will be using a relay and use the normally open and closed to make sure power isn't going to both at the same time. If i cant locate a always live wire I'm thinking to just run the wire directly from the Battery. There is a bulkhead/grommet behind the Battery. Does anyone know if I can push a wire through there? Ideally I want to try and find some wire that is already inside the car. 

There is a red controller box inside the door panel which i assume controls locks and windows. Does anyone know if there is a always on wire in there somewhere?

[sorcerer]

20 hours ago, Lexus-IS said:

Yes i will be using a relay and use the normally open and closed to make sure power isn't going to both at the same time. If i cant locate a always live wire I'm thinking to just run the wire directly from the battery.

It's true that you won't want both the DRLs and puddle lights on when actually driving but there's also the other side to consider too.

You'll have a 'normal' power feed to the DRLs for them to work in the normal way, but when you take your 'new' power supply to them, that 'new' power will also backfeed up the 'normal' wire to who knows where, so you need to stop that too.

Auto electrics are a very strange beast. I remember a situation where every time a lorry driver put his foot on the brakes, the windscreen wipers came on. If I remember correctly it turned out to be a faulty earth connection somewhere allowing power to find an earth path through a different circuit.

[Texas]

Yes auto 'lectrics are a law unto themselves, switching neutrals ( or negatives!) and back feeding lives! Not to mention the new fangled CanBus stuff!  Proper smoke 'n mirrors magic stuff that is! 

paul m.

[sorcerer]

3 hours ago, Texas said:

Yes auto 'lectrics are a law unto themselves, switching neutrals ( or negatives!) and back feeding lives! Not to mention the new fangled CanBus stuff!  Proper smoke 'n mirrors magic stuff that is! 

paul m.

You're not kidding Paul! Thing is, it's the magic smoke that makes things work - once that magic smoke escapes, that's it, it's broken 

[Ado1379]

On 08/01/2018 at 3:14 PM, sorcerer said:

You're not kidding Paul! Thing is, it's the magic smoke that makes things work - once that magic smoke escapes, that's it, it's broken 

The amount of times I hear this at work! 😂

 

as for the problem of backfeeding other systems. A simple diode in the right place should stop this. Make sure the poles are the right way round though or you’ll get absolutely nothing on you’re LED 😉