# what's the difference between common anode to cathode?



## xx1onn (Nov 12, 2013)

I'm looking for RF controller to my RGB 5050 LED strip (5 meters) and not sure about the type of controller that can fit 
what I should I buy? common anode or cathode ?
Thanks


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## RoGuE_StreaK (Nov 12, 2013)

Depends on how the strip is set up; if you apply earth to one pin and positive to the other three to control the colours, then it's common cathode. If you have one positive and three grounds, then it's common anode.


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## xx1onn (Nov 12, 2013)

I tried to understand what you say.. but I have no experience at all ..
here is what I get


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## RoGuE_StreaK (Nov 12, 2013)

So do you actually have a strip currently or not? Is what you have pictured exactly what you have ordered, or is it only the controller or only the strip? The picture shows both a strip and a controller, so if you ordered that, then you don't need to worry.

The controller pictured doesn't seem to have all of the markings to indicate whether it's common anode or common cathode, but I'd _*guess*_ from the wire colours that it is common cathode; it has red/green/blue wires for the control, and the other wire is black, which _usually_ indicates an earth wire. Then again there's already a red wire for colour control, so maybe they think that two reds would be confusing, so there's a vague possibility that it's still common anode (positive via the black wire)

[EDIT] actually, you say RF, not IR... so are you trying to control the pictured strip with radio control rather than IR control? If so, do you currently physically own the strip shown above?
If you have it in your hands, simply find a 12V source, grab two wires, poke the ground wire into the black wire connection of the strip and the positive wire into one of the coloured lines. If it all lights up with the indicated colour, then it's common cathode. If it doesn't light up, swap the wires; if this lights up, then it's common anode.
If neither lights up, you may have just fried your strip. Plug the IR controller back in and check if it still works.

RGB LEDs are essentially three individual LEDs in one package, each with an anode and a cathode. For simplicity, they tie one of these sides together, as you don't need all six lines, you can make either the cathode or the anode "common".


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## Genes (Nov 13, 2013)

Most all of these 5050 SMD LEDs strips are individual surface mount leds on a flexible strip. There are usually individual red, green and blue leds. The controller supplies 12 VDC in a common anode, open drain configuration. What this means is that all the leds on the strip have their anodes wired to the positive supply voltage. In this case + 12 VDC. The individual color leds are actuated by their cathodes going to ground (the negative voltage) through the open drain collectors on the controller. The controller you have shown is a infrared (IR) controller and it requires a 12 VDC power supply to work. Most of these 5 meter long strips need a supply of about 3-4 amps per 5 meter length. The instructions tell you that you only need 2 amps per 5 meters, but my experience is that if you only use a 2 amp supply, the leds on the very end of the strip will be very dim because of the voltage drop over the 5 meter length. Your results may vary because of the various construction methods.
Now if you want to convert this IR control to RF, then you have lots more work to do as most of these use the IR remotes, not RF.


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