Hey I was wondering if anyone knows of a point that sees ground/negative(-) when the car is on but open circuit when the car is off.

Background is I have my footwell LEDs wired up to turn on when the doors open and they turn off when they close. They are wired just like this from guitarplayer16's thread



Now what I want to do is have an alternative negative(-) path when the car is on. I'll have a resistor connected to this so the lights will be a lot dimmer. The result will be the lights will be turned on bright when the door is opened, but when the doors are closed and the car is on there will be a very subtle glow from the lights. Now I know with it wired like how it is in the diagram that would also turn on the dome lights but I actually set those to not turn on when the door opens since I like the look of just the footwell lights so that won't be a problem. I'll also have a switch installed between the lights and this alternate negative(-) point in the event that I want to manually turn them off.

With that all said I just trying to find a ground/negative(-) point that I can tap into that is only active when either the car is ON or in the ACC position

 

Fuse #32.

Cheers.

 

haha thanks that was quick, I probably should of just posted in your thread. Now I just have to figure out what resistor I want to use to have it bright enough but not too bright.

 

Please keep me updated.

It would be a nice addition to my DIY

 

will do

I actually currently have it setup to have a subtle glow with the use of a switch and a weak ground but I have to manually turn it on each time I get in the car and back off when I'm getting out which is kinda cheesy. That's why I wanted it automated with also the option of being able to turn it off, say if I don't want to see it on a long night drive or something. Although I'll probably have it on all the time since it gives the car a nice feel when you're driving and it's very subtle.

This is my current setup:



And this is what I plan on doing:



Wish I had a assorment of resistors so I could mess around until I got my desired brightness. I'll probably just try and see if I can get an assorted pack and go from there with trial an error.

 

Resistors are very cheap

 

What is the green wire from? That is the door switch line? Won't grounding that line cause the car to alert that a door is open?

I have not read the original thread which may have answered this already.

 

Never actually looked for them before, I would hope so though lol. Hopefully I can find some in a local store.

The green wire runs to the fuse box I would imagine? Not entirely sure, I had just followed guitarplayer's instructions. I do know it's not the door switch line though, it gives you ground/negative(-) when the door is opened and an open circuit when the door is closed. The dome lights always have 12v on them and when you open the door that green wire completes the circuit for the lights to come on. It's not electrically wired directly to the door switch however.

 

It's the dome supervision wire.

 

Which if grounded would trigger an alert? Just thinking if a diode or relay needs to be in the loop with that manual switch being inserted. I do not know enough about the entire circuit to know if there will be any issues with the OP's plan.

 

Using the dome supervision wire will not trigger an alert. It's not the door wire.

I would use a relay for the OP's purpose as you mentioned, though.

On another note, fuse #32 is only powered when the car is ON, so the alarm would not be triggered (alarm doesn't trigger when car is on).
Now that I look back at the OP's diagram, I don't think it will work.
Essentially when you hit the switch, it's providing a positive current from the power seat fuse, and another positive current from fuse #32. Not good.

 

Did some more research.

You'll want to use a relay.

Wire it so that by default it's negative to dome supervision wire and positive to power seat fuse.
Then have the trigger wire from fuse #32 (when the car is ON) to change the negative path to a body ground (use ring terminal to bolt under steering column) instead of the dome supervision wire.

 

Wait I'm confused lol. I thought fuse #32 was ground/negative(-) when the car was on? That's what I was looking for in the original post. I do like that idea of the relay though, I didn't even think of that. Using the relay I wouldn't even have to worry about figuring out what resistor valve I need to use since the ground point I'm currently using puts the LEDs at my desired brightness. All I would need to buy is the relay and be done, using the negative path to a body ground I'm currently using.

 

Fuse #32 is positive, and negative would be body ground.

 

I don't think the car has any switched grounds, if you want your lights to be dimmer why not just wire a resistor in series with it?

If you want it on at night with your headlights then tap into the glove box light or center console light wires.. just tap that positive wire and put it to your LED+ and tap the negative wire and put it to your LED-. If your LED is too bright wire a resistor in series with the LED to reduce the current through it and hence it's brightness.

If you do it this way then with the light switch..

- Parking lights on = LEDs on
- Headlights on = LEDs on
- Headlights off = LEDs off
- Parking lights off = LEDs off

To get your desired brightness.. qualitatively..

If you buy a rheostat then you can wire it in series and adjust the resistance of it until you have your desired brightness, remove it from the circuit and measure the resistance across it at your desired brightness. Then buy a resistor at that resistance and wire it in, or you could just leave the rheostat in and have the option of dimming your LED. You should have a starting point though, what is the max current at what voltage for that LED? So you can get an idea of the needed resistance..

And quantitatively you can use ohm's law. P = IE or E = IR, transpose however needed to calculate your needed value.

- Do you have a datasheet for the LEDs?
- What is the rated current for the LED?

Pick a resistor that reduces the current through the LED to a certain luminous flux based upon the spec sheet, if you have one for that LED or can find one.

 

Good info, although he already knows most of what you just posted.

He wants a setup that:

1. Turns on when you lock/unlock the car via dome supervision wire
2. Turns on when you switch the car on.

Pretty much multi-source power for his LEDs.

 

I see.

There is one switched ground now that I think of it. The door open switches in the door jambs, I have my supercomputers sills wired in to them so they turn off when I close the door.

They pass a ground only when the door is open and no longer pass it once it is closed.

Use a relay with the switched ground, will have to think about it for a min but could come up with something using that switched ground.

 

This will work with an automotive 5-pin relay:

Relay Pin -- Function -- Wire to this..

Pin 85 -- Coil Ground -- Switched Ground (from door jamb switch)
Pin 86 -- Coil Positive -- +12V constant
Pin 30 -- Switched Output -- LED +
Pin 87 -- Normally Open -- power seat + Wire
Pin 87A -- Normally Closed -- Accessory Power + or center console/dash light +

This will have the function of..

+12V is always present on the coil of the relay, when you open your door the ground is applied to it and it switches to the position that applies +12V from your current wire setup to activate the LED when you open the door. When you close the door the LED will extinguish.

When you put the car in the ACC/RUN position, +12V will be applied to the normally closed leg of the relay, which with the door closed will supply +12V to the LED turning it on. If you wire it to the glove box light + wire or the center console light + wire then it will not turn on the LED until you turn on the parking lights or headlights.

When the car is off the LED will be extinguished, provided the door is closed so there will be no drain on your battery.

For the negative end of the LED I would connect it directly to ground (pick a spot on the chassis, somewhere near the dash that has bare metal) and solder in a resistor between the ground and the cathode of the LEDto get your desired brightness.

The +12V going to the coil leg of the relay will have to be an ALWAYS hot wire though, so it needs to be hot even when the key is out and the car is all locked up, since on this one we would be switching the ground, if the power seat wire matches this description you could wire it to both pins 86 and 87.

If you can find a solid state equivalent of a 5-pin relay like this that would be more ideal, no clicking noise.

 

I honestly didn't see both your responses till a couple days ago for some reason I've been busy with other stuff, finally have some time now to work on this again. Ok so after reading through your posts a few times and brainstorming with pencil and paper, this is the final plan thanks to you guys





Features:

• If car is ON or in the ACC position the footwell lights are dimly lit, they get bright when the door opens and dims afterwards
• With the car ON or in the ACC position, the dome lights aren't dimly lit or come on when the door opens. The dome lights can still be manually turned on by using the stock switch at the dome (The "1" position)
• The switch that's inline with the wire coming from Fuse #32 ACC allows me to turn the always on feature off if I don't feel like driving with the footwell lights on for some reason, they will still turn on when the door opens
• Wired like this still allows me to have that dimming effect when you close the door and the lights slowly fade out

Final thing I have to do is still figure out what resistor I want to use. That rheostat idea would be great. I might not have to even worry about it though because the ground I'm currently using is kinda weak and actually has them at pretty much the perfect brightness for me. It would be cool to have it adjustable though.

 

Yep, that should work. A million different things you can do with electronics.