CCool, whenever u can get a pic for me please, im going to be installing a kit soon n im looking for controll unit places

 

So I went to Radio Shack to get a multimeter and some LED's, got the multimeter, got confused with the LED's. I only found one labeled 5v (source power), is that correct? Everything else was 2.1v, 3v, 12v, etc.. Could I get a lower volt? The colors I want were in lower volts, the only 5v was blue.

Also how exactly do you wire it? Is the green wire power? When it comes to wiring and volts and all this stuff, I'm lost.

And with the multimeter, which setting do I use? It has like 15.

 

Maybe if you could point me in the right direction on this site:http://www.skycraftsurplus.com

 

GTVEVO, you're saying one thing but in your other thread you say the exact opposite. Trust me, I've checked this out myself. You can not use the green wire to directly power an LED or indicator lamp. This wire drops it's ground when the pump see's above 40psi at it's pressure switch. When the ground drops on this wire, the yellow LED on the SMC controller lights up letting you know the pump is working(pressure above 40psi). Below is a quote from your other thread. The bold type describes exactly what the green wire does.

You need a relay with the LED's ground wired to the normally closed terminal. So when the ground drops on the green wire, the relay will then ground your LED.

 

Exactly so if you ground the led on a common ground and use the power that is pushed though it during spray it will light up just as it does in the control box. This wire is either grounded with no power when the spray is off, or it has power once the spray is on, read it. Hopefully this makes sense. On the AEM box the switch doesn't turn on until it gets voltage after the ground is pulled away from the pump making pressure.

Let me make it simple for you and since you have personally tested this you would know.

Green is grounded when pump is <40psi, Green has voltage after the pump switches it (by dropping the ground on the pressure switch at the top) to around 4.5 volts.

 

EDIT: On further inspection of the controller board itself, I can see how 4.5v could be found on the green wire when it's ground is dropped. It's a fairly complicated circuit for me to completely understand but I can sort of see how the logic works. When I talked to Steve about this before discussing how to wire in a spray-on LED, he only suggested using a relay to power a 12v LED off the green wire. So when I tested the green wire, I only tested for the dropped ground and not for the change to 4.5v. So I tested with the relay and 12v LED and got it to work that way.

I have no problem admitting when I'm wrong and apologize for doubting you GTVEVO. So Kerr, like GTVEVO said, you can use a relay to power a 12v LED if you like or find a LED in the correct voltage range to run off the green wire directly.

 

Thanks dude for further inspecting and understanding that we both suggested a valid possible option.

 

Ok, so now that we are square that I can just wire it in, what is the correct voltage range? Is it anything less or equal to 5 volts, or <=4.5 volts? Can I get a 2.1v or a 3v, does it work that way?

 

Depending upon what voltage of led you want to use you will want a resistor to reduce the voltage going to it otherwise I would think it will burn out quickly. I had found a bright blue that is exactly 4.5 volt somewhere back when I researched this.

 

So can I get a 12 volt and not worry about getting a resistor? I am bad with electronics, I really don't know what I need. All I know is I want a green light and a yellow light.

 

Right if you use the other way you will need a Relay and your lights to control the switch so to speak as HmanEvo described and you will be powering 12volts to the system so you can run 12volt lights.

 

I would still recommend running a resistor no matter which way you decide to go. It helps to protect the LED from any spikes. Sometimes you can find a LED with a built in current limiting resistor. That's what I used. I picked up a 12v LED from radioshack pt# 276-271. This can be wired to the vehicles 12v system directly with no problems. Of course you still need to use a relay to switch it on.

Here's the formula for figuring out what resistor you'll need.

(V1 - V2) = R
C

R= Resistor in ohms

V1= your systems expected voltage. If you decide to go the relay route to run a 12v LED, you can expect to see anywhere from 13.5-14v with the vehicle running. If you're planning to attach the LED directly to the green wire, you can plan on roughly 4.5v but I would use a voltmeter to confirm this.

V2= the LED's voltage rating.

C= the current in Amps that the LED is rated at. Typically found between 10-20mA.

Heres an example for wiring directly to the green wire. Say you have a LED rated at 3v and a current rating of 12 mA(.012 A). The voltage on the green wire is found to be 4.5v

(4.5v - 3v) = R
.012 A

R= 120 ohms

So now you need to find a resistor rated at 120 ohms or as close to that going bigger depending on if they carry one in that size. You should also make sure it's at least a 1/4 watt rating. Also when attaching the resistor, you want to make sure it is soldered to the LED's anode which is typically found to be the longer pin. This pin goes to power and the shorter(cathode)pin to a ground.

 

(Assuming the actual voltage of the green wire is 4.5v) If I go less voltage on the led (3v) I need a restrictor, if I go more voltage (12v) I need a relay?

As an example, say I went with this exact LED, I would need a restrictor at 115 ohms?

I did (4.5-2.2)/.020=115. (I'm not sure if the 2.2 is correct)

 

Yes and I'm sure it was a mistype but it's called a resistor. If you decide to go with a 12v LED, you will have to use the vehicles 12v system to power it which will require using a relay in conjunction with the green wire to turn it on.


Yes the 2.2v(typical forward voltage) is correct and what you look at. So you would need a resistor of at least 115 ohms. If they do not have one rated for 115, you look bigger for the next closest rated resistor. You're getting the hang of it.

 

Ok cool, I think it will be easier to go the <4.5v route. I'm going to go to the store and see what I can find, maybe get it all done today.