Relay wiring question shift light

[ErikTande]

My shift light isn't strong enough to light up a whole string of LED's, so I added a relay (much like rewiring your fuel pump for more power). It helped a lot, but the LED's still aren't as bright as connecting directly to the battery. Why is that? I have tried 2 different relays but they both give me the same result. See vid:


Problem is the same when wired in the car as well.

You must be logged in to view this image or video.

 

[1990TSIAWDTALON]

Erik are you wiring in "series" or "parallel"? It should be in parallel. Series would draw down the voltage from each led pulling its microvolt until they add up enough to drop voltage to the string. Just to clarify for you.

 

[luv2rallye]

Need to see wiring diagram of how relay is connected.

 

[ErikTande]

I have no idea if it's series or parallel to be honest. I'm terrible at electrics. Here's how I did the relay:

You must be logged in to view this image or video.

 

[1990TSIAWDTALON]

Ok, from the "Positive output" run ALL hot leads for the LED's to that (all in one, not daisy chained) and then ground all of the negatives. This way all the LED's see the exact same 12v all of the time. So all RED wires of the LED's hook to the "Positive output" and all BLACK wires on the LED's go to any good ground.

Daisy chaining is when you hook one red to positive then that bulbs negative goes to the next ones positive and so on, just explaining so you understand what I was meaning.

 

[ErikTande]

The LEDs are all connected together with 1 wire for the positive and negative, like this:

You must be logged in to view this image or video.

Powered by shift light alone = DIM
Powered by shift light w/ relay = Brighter
Powered directly by battery = BRIGHTEST

 

[91-GS]

Just so you know, this is how a typical LED strip is built:

You must be logged in to view this image or video.

As you can see it consists of sets of diodes (that are wired in series, or 'daisy chained') that are wired in parallel so you can cut off few sets and each piece will remain functional.

Why are you using a relay instead of a transistor? While either one will will work fine, it seems that a transistor will be a better choice in this situation since it takes much less current to operate and therefore won't load shift light's electronics nearly as much.

As far as brightness goes, from looking at the video it seems that you miss-wired the relay and that is causing issues.

 

[1990TSIAWDTALON]

Erik can you measure voltage on the hot side of the LED strip for each situation? They like 12-13.5 volts and maybe the shift light isn't supplying that? One COULD wire that relay to "trip" with the shift light output then connect 12v into the relay from a good 12-13.5 volt source that then feeds your LED strip. If its confusing I could draw it for you.

PM sent.

 

[luv2rallye]

Also to do a proper test you need to use the car's battery. That little 9v is probably being loaded down (doesn't have the capacity) to drive both the LED's and the relay's coil which is why connecting just to the 9v is brighter.

 

[ErikTande]

Why are you using a relay instead of a transistor? While either one will will work fine, it seems that a transistor will be a better choice in this situation since it takes much less current to operate and therefore won't load shift light's electronics nearly as much.

I had no idea what a transistor did to be honest. So I looked it up, found this video (which is my situtation EXACTLY) and I ran to radio shack and picked one up. It's working perfectly now


Thanks for the help everyone!

You must be logged in to view this image or video.

 

[ErikTande]

Nevermind, it was working perfectly on the desktop with 2 different power sources (2 9v batteries). Once I wired it in the car (obviously both on the car's single 12v system) the LED's just stay on constantly. So I brought a 9v battery out to the car and it started working again.


I'm stumped.

 

[luv2rallye]

I'm an experienced electrical engineer. Your explanation in your video sounds completely wrong and you probably shorted out the transister due to improper connection. Show (or PM me) your wiring diagram.

 

[ErikTande]

I don't think it's shorted, it still works when there is a separate power source for the shift light and a separate power source for the LED like in the video I linked. I'll post a diagram here in a bit.

 

[ErikTande]

Ok, so here is how I got it working with a transistor. I even got it working in the car like this. But obviously I can't be lugging around 2 batteries all the time : P

You must be logged in to view this image or video.

 

[Cox Abele]

Something tells me that the relay setup isn't working properly because there is a resistor on the board for the LED. What is the output voltage on the positive side of the LED? Next is amperage- LEDs require very little amperage to illuminate, so it may not be sufficient amperage to switch the relay and likely the case of the dim LED array.

Knowing the circuitry of the circuit board is imperative. Knowing which is the switching circuit for the factory LED is imperative assuming you are using the wiring from the board's LED. Below X rpm, there is an open circuit. Above X Rpm, a circuit closes and allows current to pass through the led. I'll need to know which side/polarity of the circuit is the switching circuit. This will tell me which kind of transistor you need.

A little more information will help me figure this out for you. I'll draw you up a schematic once I know a bit more information about the board.

 

[luv2rallye]

1) What transistor (number on it) are you using? (Need to know if there's just 1 power transistor in that TO-220 package or is there more circuitry inside.)
2) Is the shift light circuit board designed to be used with a 12V supply? What's it's max current output?
3) Do you have the circuit diagram of the shift light circuit board? We really need to know, at bare minimum, what it's output circuit is.
4) It's really unlikely that you can just connect the shift light circuit board positive output to the transistor's base (red wire) without going through a current limiting resistor (will burn out the transistor's base-emitter junction). The resistor value depends on the led's current draw, the transistor's currrent gain, and the shift light circuit board's output voltage.

 

[ErikTande]

1) What transistor (number on it) are you using? (Need to know if there's just 1 power transistor in that TO-220 package or is there more circuitry inside.)
2) Is the shift light circuit board designed to be used with a 12V supply? What's it's max current output?
3) Do you have the circuit diagram of the shift light circuit board? We really need to know, at bare minimum, what it's output circuit is.
4) It's really unlikely that you can just connect the shift light circuit board positive output to the transistor's base (red wire) without going through a current limiting resistor (will burn out the transistor's base-emitter junction). The resistor value depends on the led's current draw, the transistor's currrent gain, and the shift light circuit board's output voltage.

1. I'm not sure, I don't have the package with me. I can update that later tonight.
2. Yes, it's designed to use a 12v supply. I *think* the output is 6v, but I'm not sure.
3 I don't have a diagram, sorry. It's this shift light: http://www.ebay.com/itm/1000-11000-...-Gauge-Shift-Light-Lamp-Red-LED-/261264855451
4. That's Greek to me, sorry


I don't know if this helps, but with the diagram I posted using the transistor, the shift light with the LED's works perfectly, and nice and bright too. I even took a vid. (I set the RPM dial really low so I wouldn't bother the neighbors with a 7000 RPM test

You must be logged in to view this image or video.

 

[luv2rallye]

1) Ok from your post 10 video you said you're using a TIP120 transistor. This is a 5 amp max NPN darlington which should be more than enough for your leds.

2) What/where did you get this shift light circuit board? Is this the board you pulled out of the shift light (http://www.ebay.com/itm/1000-11000-...mp-Red-LED-/261264855451?afsrc=1&rmvSB=true)? I couldn't make out what you called it in the video.

3) I looked at the TIP120 spec sheet and I think if you put a resistor in the 200-500 ohm range (value not critical and any low wattage) in your shift light circuit board positive output to the transistor's base (red wire going to the left lead viewed from top), you should be good.

 

[ErikTande]

1. Post #10 isn't me, it's just a video I found that helped me figure out how to wire a transistor.

2. Yes, I pulled the board out of that shift light from ebay.


Can you post a diagram or explain how this should all be wired up using one 12v power source? The only way I've been able to get it to work is with 2 batteries like I posted in post #14.



Thanks for the help, I appreciate it!

 

[luv2rallye]

In your post 14 diagram connect the shift light circuit board input negative to the 12v battery negative (the other battery in your diagram). Then connect the shift light circuit board input positive to an ignition switched +12V source (something that gets power when ignition key is on). Then put the resistor in where I previously said.

 

[ErikTande]

So like this? I did try this but it didn't work, the LED just stayed on all the time. I didn't have the resistor though.

You must be logged in to view this image or video.

 

[luv2rallye]

Where you show the shift light circuit board "in", I had assumed that it is the power for the board (since you have the 12V battery there) - NOT the signal to trigger it. Is that correct?

If that's intended to be the trigger signal (instead of board power), it should go to the car's tach signal (or ignition power transistor pin 4 or ECU pin 58). Then you still need to connect the +12V battery to the shift light circuit board's power (red wire shown on the shift light for power). You also need the resistor to prevent TIP120 transistor damage.

{Note the way you show it above, the LED would stay on since your trigger (12v battery) is always putting positive voltage there (on "in" +). Voltage must be removed to make LED go off. As just a test you can intermittently touch the 12v positive on/off there (as long as there's also power to the board)}. You also still need the resistor to prevent TIP120 transistor damage.

 

[91-GS]

Erik, take a picture of the shift light's board and the transistor you are using, that way it will be easier to see what needs to go where.

 

[luv2rallye]

Reread my post 22. I made some corrections.

 

[ErikTande]

The issue has become convoluted, let me simplify it.

I have an LED hooked up to a 12v power source through a circuit board. The LED is only getting 6v from the circuit board. How can get 12v to the LED?

Keep in mind I can't eliminate the circuit board, I need it to tell the LED when to turn on.

You must be logged in to view this image or video.