Monday, August 26, 2013

Enter Raspberry Pi

Fast forward to 2012, the year the first Raspberry Pi Model B computers hit the market. I got one pre-ordered very early, but still had to wait a couple of months for it to arrive. I can't remember exactly when it arrived, but I found first pictures in my collection to be dating back to October.

It must have been around that time that I found a 5 meter package of LED strips on sale at a local grocery store. It was one of those typical packages... 5m of RGB LED strip, cuttable, with connectors to go around corners, a power supply and a small but colorful infrared remote. I got one of these with the explicit intention to play around with it, so I was not that disappointed to find that the capabilities of the original package were kind of limited. I really wanted to hook this up to a computer, and what would be better suited for this than a Raspberry Pi?

And so I started fiddling again. This time I was not bound to DMX, so I figured my best choice would be one of Adafruit's PWM servo boards. I didn't intend to run servos from it, but since it was capable of outputting PWM at 5V i figured this would be enough to drive one of those ULN2064B chips I had already used before. The LED strips themselves turned out to be running at 12 volts once more, so this was all kind of a déjà-vu to me. The board also had a total of 16 output channels - enough to cut the strip into five pieces and control the red, green and blue values for each one individually.

First experiments looked promising:

Rasbperry Pi with PWM board driving four regular LEDs
So I hooked up a ULN2064 I still had from earlier work to the PWM board, used the power supply from the original package and things literally got brighter:

The video shows the complete setup: Raspberry Pi, PWM board, ULN2064 and LED strip.

After that, all I had to do was get a few more ULN2064s and a case to store the circuitry in.

Fitting the circuitry into a box
For connections to the outside, I used 4-pin Mini-DIN connectors, as they allowed me to bundle the necessary lines (one for red, green, blue and a V+ pin) into a single connector without using too much space.

Fitting the connectors

How it will once look when finished (lower case is still open)

Insides almost finished

One more inside shot
I ended up cutting the original strip into four pieces, because I found that a 4-pack of LED sticks I once purchased at IKEA also ran off 12V and worked perfectly with this new dimmer device, and so I used one output to power these.

Skip to today: After finally aquiring the materials needed to etch my own PCB boards, I am currently in the process of redesigning this dimmer. Click here for the follow-up post.

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