Posts: 62
Joined: Thu Dec 26, 2013 4:46 pm
Location: Westerkwartier, Groningen (NL)

5050 led questions

Fri Oct 05, 2018 2:05 pm

Dear members,

Found a dymond 5V usb powered double string of 16 x 5050 rgb leds in the shop. With a remote control. They are presented in this video Their intended use is behind a television.

But I am doubting if they can be driven, individually, by the Raspberry Pi. The description on the strand of leds is G R B 5V and the examples I have found have Gnd DI Cl 5V. The actual wires going to the strip have corresponding colours and the 5V is black.

Then there is the 5V question. Can the raspi be used to deliver the 5V for the strip or should I use its own power supply?

Many thanks,
peter blok

Posts: 13
Joined: Wed Oct 17, 2018 7:46 pm

Re: 5050 led questions

Thu Oct 18, 2018 8:51 pm

If the strip can be powered by USB, then it draws little enough current that you can power it through the pi.

I'm not sure what you mean by driving them individually. Do you mean each color individually? The LEDs will be arranged in parallel on those strips and so there is no way to address one specific light within the strip. You only have control of individual colors.

Connect 5V to the 5V pin, then the difficult part is that you will need to connect each of the other pins individually to GND. When you connect each of the other pins to GND, you will individually switch on the colors. G for Green, R for Red, and B for Blue.

Of course, you cannot sink those through the pi's GPIO's, not only because the 5V will murder your pi, but also because the current that you need to sink is FAR GREATER than what a GPIO can handle. So you will need 3 N-channel FETs, and 3 resistors around 10k ohms. Connections as follows;

S --> GND
D --> LED strip color pin
G --> Some GPIO on pi
G --> Resistor --> GND

When you switch on the GPIO pin, it will activate the FET and light up the corresponding color on the light strip.
You can also use PWM to control the brightness, and in this way, individually control the brightness of each color, which gives you the ability to set the overall light color, as well as the overall brightness.

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