Cathode rgb led. Is it possible?

Hello. I am making my own Arduboy. I am using @Mr.Blinky 's homemade package. @MLXXXp told me that I need to use an anode rgb led, for the leds on the Arduboy, but I only have a cathode one. How do I connect a cathode one instead of the anode one? is it possible? Can I convert? Keep in mind I’m using @Mr.Blinky 's homemade package and using the alternate pro micro wiring.

It only costs a few dollars to buy the correct LED … it might save you a heap of hassles :slight_smile:

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If you want to use an common cathode RGB LED you will need to change the libraries to support it. Doing this will take quite some effort. Frankly it will be much less effort to just buy a common Anode RGB LED or use individual LEDs.

It would be a good excuse to buy some of these big 10mm ones (Anode fog type)

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If you absolutely don’t want to change and recompile the software to support the opposite type of led you could just built an rtl (resistor transistor logic) inverter for each color channel. This way with a few extra components the inversion will be done in hardware. Or just use a cmos inverter like the 74hc04.

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I guess I’ll use separate leds. But I wont get the same effect :slightly_frowning_face:. But how do I use the cmos inverter? I’m pretty sure I have that chip so how will I use it?

Input of the inverter channels are fed from where the common anode rgb led’s cathodes are originally wired to the atmega, output goes to common cathode rgb led anodes. Of course you’ll also have to power the inverter chip with vcc and gnd.

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Umm. How do I know which leg on the chip is which? Can you draw a wiring diagram then send it?

By using the magic spell word datasheet :wink:

At this point I’m wondering do you have a 74HC04 (or similar) lying around? If not then buying a common anode RGB LED would make more sense then buying an 74HC04.

You could design your Arduboy in such a way that you can use the seperate LEDs for now and can easily ‘upgrade’ them with an RGB LED in the future.

But to keep things simple, If you can’t make up your mind about the LED, leave it out for now. You can add it later.

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I got the 74HC04 from the Elegoo super starter kit for the Uno. Thanks for the data sheet! But, how do I know which diagram is right? But I’m still wondering how I connect it. I didn’t really understand what you said @sjm4306 . So, if I use this inverter, will it basicly convert the cathode leg to anode? I’m still kind of new to chip stuff.

Edit: So it turns out I do not have that chip. I have 2 other chips called L293D and 74HC595. I guess I just got mixed up with the last one 'cause they both start with 74HC (man what is wrong with me lately). Can I use any of these? If I can, can someone send me a datasheet?

Those are not suitable (The L293D is a motor driver and the 74HC595 a shift register)

To obtain a datasheet try entering the partnumber followed by the word datasheet in Google. Works best for me.

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I know the Arduboy has and rgb led. It can look like different colors too right? Like yellow maybe? Is there a pin for more leds on the pro micro or just blue green and red? Have you seen any games using other colors than red blue and green? If not I can just use separate leds. If so…well, I don’t know.

All the games I have seen using the LEDs - and there are not many of them - use them for effects snd the colours are not overly significant. As MrBlinky suggested just leave the the LEF out until you gave the correct one.

Theoretically the tri-colour LEDs can make blends of different colours but in reality you still see a blue and a red led - not a purple colour. They are just closely located. A frosted version may make this less obvious.

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Ok. I’ll use separate ones then. I’ll start making my Arduboy tomorrow, that is if all my components are in that big box from Amazon…

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Okay…so um I bought the rgb led.

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Good decission!

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