Connect Common Anode RGB LED's to Common Ground RGB LED's





Introduction: Connect Common Anode RGB LED's to Common Ground RGB LED's

During my RGB led fan project I accidently bought common ground rgb leds while my circuit was disigned for controlling common anode rgb leds.
Now that I have run out of common anode RGB leds I tried to come up with a solution to somehow connect common ground to common anode.

After a few tests I came up with the circuit below. Using 3 pnp transistors it inverts the R-, G- and B- to R+, G+ and B+.
In order to create ground for the led's I connected 3 rectifier diodes to R-, G- and B-.
I am very happy with the results of this circuit and the fact that I don't need an additional wire for ground to drive the common ground leds.

I added the eagle files including the circuit and board. (NOTE: on the board I used BEC PNP transistors)



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    I had already figured on making a waterproof box for it or run it into the car itself. I am just not technically inclined with electronics so am having some trouble. I do know it is a 22" RGB Scanner bar as shown in the website link I posted. It had a separate controller box that plugged into it with a transmitter to change the lights and patterns. I found a better controller though that would run on my phone so that was the initial reason why I wanted to do this. There were 11 wires that ran from the light to the controller box, I figured out which would be my positive and which three would be my R,G,B neg but didn't realize they would be opposite from my new controller. I tried to look for any convertors all over the web but have yet to see anything other than what you had come up with. I don't want to bother you is there a way you could help me figure out what all parts I would need to make something work? I can provide any information about the lightbar you would need. I have someone who can make the board for me as well. I just need a parts list and a diagram. Like I said I am not electronic inclined so talk of mosfets and such makes no sense to me haha. I would really appreciate if you could help me with this as I would like to have my lights up and running again and not have to use the old controller it came with.

    Ok I need some help from someone please. I know this is old post but could use some advice as I am not completely electronic swavy. I have a Oracle WiFi controller used to control led light bars via remote or cell phone in am app. This is a common anode controller. I also have a rgb illumination grill bar for my car. This had a controller box with a remote to control the colors patterns etc. as shown here. I wanted to use the WiFi controller instead which I know I can however after figuring out what wires were my pos and than my r g and b I found out that this is a cathode led bar. So my delima is would this chip that you made work for me? Or what can I make that would go between the two to convert it basically. I don't want to get a different light bar as this is made for the grill being able to be outside and the controller I bought is expensive as was the light bar. Please someone help me as I said I am not that savy with electronics but if I had a part list and how to do it I could have my dad make it for me as he has a electronics degree but don't think he has ever dealt with this before so having diagram and parts would help .Or if someone sells something like this. Please let me know I can also be reached at

    U would need to build a sealed isolated box as this is a car situation so the pcb would be exposed to the elements. For your purpose I think those rgb bars will use quite a bit of current so mosfets would be your best option. I don't know if there is a commercial option that uses my concept but u might look for rgb common anode to cathode converter on ebay maybe now they have made those. When I made this instructable there were none.

    Does anybody know the transistor values and or part numbers for this? Diagram is straight forward but doesn't show values of transistors specifically the t1 t2 and t3

    Values depends on the amount of leds u are controlling. Small TO-92 can handle 200 ~ 1000 ma for more u need large heatsink mountable transistors or mosfets. Current is for each channel.

    Awesome mate, thank you U make it look so simple!!

    OK, because I
    am new to the electronics, and thinking this through, all of these CCTS shown are for LED strip only not direct RGB led like I want to use.

    With the AQ5 it will control the colour output via it's software on those pins, so I need to take these outputs and feed them into my 4 RGB leds. Which will be used to show TEMP in a sort of colour format, RED=HOT, BLUE=COOL etc..and change based on temperature.

    As I want to just use 4 x single RGB LEDS i need some additional changes to prevent damage to the AQ5 since its designed for 1 rgb led.

    1. I just
    add suitable resistors to each RGB driver output/LED based on their data sheet for MAX brighness

    R: (5V-2.2V)/20mA = 140 Ohms
    G: (5V-3.5V)/20mA = 75 Ohms
    B: (5V-3.5V)/20mA = 75 Ohms

    2. I need to control the current and make sure that when all LED are on does not draw more than Imax20mA from the AQ5, so current limiting regulating/transistor would be required?

    3. Since the AQ5 will control the output then these 3 'triggers' will feed into 3 transistors to drive the 3 colours of the RGB leds, just not sure what transistors 2N3904 ?

    4. All RGB leds will be in parallel connected directly to a molex power connector to the 5V rail or could use 7V if required by linking 12+5 together as the Common Anode? Should I use 12V?

    From all this, how difficult would it be to draw up an appropriate diagram and CCT board to be etched out, could you provide a rough cost an payment via paypal?

    Thank you again!


    I have added schematic and simple board design.
    U have to find a fab house yourself I don't manufacture pcb's.


    WOW Mate this is awesome! Shoot me your paypal mate I can make a contribution as this is very generous of you!

    Let me know if you have my email, please feel free to send me a message!

    This will help me out a lot, appreciate it mate!!