# Can you determine RGB pinouts with a multi meter?

I have a Swiftech Apogee XL2 that has an addressable LED inside it. I want to connect it to my other RGB setups but I need to know the pin signals and voltage of the LED. I have a multi-meter at the moment but I can buy anything else that's needed. What do I need to do? Can anybody help? I only have very basic electrical knowledge but I'm ready to learn. I've included photos of the block and the connector in the link below. Thanks!

https://photos.app.goo.gl/wtKxNEYCA6qHwcP3A

Based on my research, I'm certain it's one of these two variations below. I'm just not sure about the voltage and how to identify the pin order.

https://rog.asus.com/forum/attachment.php?s=6ebdc99c23d18e50b41c1d879d3513ac&attachmentid=71018&d=1517278100&thumb=1

• 3 pins? It's obviously not the 4 pin version on the right, that's for non-addressible leds. Oct 7, 2018 at 23:22
• Look closely at the pins on the connector. Use a magnifying glass if you must. Which one is it? 3 pins or 4? If 3, which seems likely, you cannot directly connect it to other direct RGB units. You would need a 5 volt serial data stream to set the intensities. But that is putting the cart before the horse. How many pins? Oct 7, 2018 at 23:50
• @WhatRoughBeast it's a 3 pin connector and the manufacturer calls their RGB "addressable" so I'm thinking it's more likely a 5V addressable RGB, Thanks for your input! Now I need to figure out the pin signals. Oct 8, 2018 at 15:13
• Realistically for an undocumented addressable product your best bet is likely to mount a sacrificial unit, give it current limited supply through your best guess of pins while watching the draw and feed it your best guess of control. With luck you won't smoke many before you figure out the answer. Apr 2, 2019 at 18:07

Some multimeters have a diode tester so you could use that on any number of LEDs to find their forward voltage. This may not work on adressable LEDs. Other than this you can try to identify the LEDs and Google them to find the spec sheets Fv at the least, but bear in mind that this is usually fairly inaccurate but it could be your only option.

You could also check the output of the PSU for the LEDs and go from there about a correct supply voltage.

If I needed to test the pinout I would:

1. Try to find a schematic in the manual
2. Tap each contact with a lesser supply voltage till you get lights
3. Attempt to find the schematic and specs of the IC that is being used to make the LEDs adressable throughout the strip. This might also reveal the reccomended input as I would hope the ICs had a constant current driver (better running conditions for an LED than contant voltage).

Hopefully this is what your looking for!

• It seems like this LED connects to a motherboard fan header. You can check the voltage of the fan headers in your motherboard manual or online I would guess. Oct 7, 2018 at 23:30
• Thanks for your reply! I know that it's either 5V or 12V. Would my multi meter have enough power to light up the LEDs, or is that not how a multi meter works? Oct 8, 2018 at 23:18
• Possibly not, but it would have enough power to run the LEDs at their Forward Voltage, which is the the voltage at which current flows through the LED. If this were me I would get a 5 or 12V supply and just tap the connectors with a 5V supply and see if they are bright enough. If not I'd suspect that they are 12V. Oct 10, 2018 at 2:48

Popular addressable LEDs are typically powered by +5v. The page you link to has a link to a controller that cautions the user not to insert the ALED into a fan connection as the voltage (+12v) is higher than what is allowed (+5v).

So it is somewhat safe to say you are dealing with +5v.

If those attachment arms are made out of metal, perhaps they are grounded as well. Try probing the pins of the connector and the metal arms. If you measure a short circuit it is very likely that you will have found ground.

More often than not the power rail is opposite the ground pin / wire and the data lines are in the middle.

So if you feel confident with 'somewhat', 'likely' and 'often' you could give it a try..

This identification depends on parasitic diodes within the package. Assuming you have a digital multimeter, usually the red lead is positive with respect to the black lead when doing a diode test (confirm by reading the manual or by testing with a known diode).

If you test the leads relative to each other you should be able to identify one which tests as a diode (about 550-700mV reading on the meter) to each of the other two leads when forward biased and overrange when reverse biased). That will be the data lead.

Connect one of the other two leads to +5 through a 1K resistor and the remaining one to ground. Measure the voltage across the chip (ignore the data line). If it reads about 0.7V the GND and +5 are reversed. Swap the leads and measure again. If it reads more than about 1V that should be the correct +5 and Gnd connections. Do not use much less than 1K or the chip could be damaged.

You can then try connecting 5V and hope the smoke does not come out. Use a separate 5V supply, not your motherboard. When you connect it to your motherboard use the same polarity and at least temporarily put the 1K in series with the data line and preferably a polyswitch resettable fuse in series with the supply line to protect the motherboard.

No promises here, you may burn it out, or you could conceivably damage something else (such as the motherboard).

simulate this circuit – Schematic created using CircuitLab