Lots more LEDs

Look what arrived from China this morning…

Interesting...

Interesting…

Ahhh... LEDs

Ahhh… LEDs

That’s pretty quick – around 2 weeks and at this time of year. It’s a reel of 1000 RGB SMD 5050 LEDs, for 2.6p each 🙂 They don’t have a built-in controller (which is why they are so cheap) but for (say) lighting panels you don’t need to control each LED individually.

I haven’t organised any circuit boards (yet) so I had a bit of a rummage in my adpator box to see if I could find anything that would let me have a play with one…

 

 

SSOP-16 Adapter

SSOP-16 Adapter

It’s not a perfect fit but you get (from left to right): 2 pins, 2 pins, skip one, 2 pins, skip one. The main thing is that you can get a connection and there’s no risk of a short. Here’s the finished article:

Adapter abuse!

Adapter abuse!

So it’s not the prettiest bit of work but it does the job. The pinouts are:

RGB LED pinouts

RGB LED pinouts

The datasheet states a forward current of 30mA and forward voltages of 2.0 for red and 3.1 for green and blue. That gives resistor values of 100Ω and 68Ω respectively.

Chuck it in a breadboard…

Breadboard with a few other bits going on

Breadboard with a few other bits going on

All LEDs connected for white:

110mA for white

110mA for white

Disconnect blue:

80mA for red + green

80mA for red + green

Disconnect green:

50mA for red

50mA for red

That’s all consistent with the datasheet – the yellow LED on the breadboard pulls 20mA so that leaves the readings showing 30mA per colour in the RGB LED.

Don’t see any point in playing with any more – I’ll knock up a basic panel idea that will allow me to connect it to a micro-controller for PWM dimming of all LEDs on the panel (that provides brightness and colour control). Even a tiny45/85 will do as you can get 3 PWM pins out of those. Add a MOSFET per channel and it should be good to go. I’ll do a bit more research first though. The MOSFET route would also require 3 resistors per LED so a dedicated constant current LED driver IC might make more sense. We’ll see…

 

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