Wednesday, June 21, 2017

Alps 48 RGB

48 Key Per Key RGB - Rainbow Cat Vomit 1.2 PCB

  • 4x12 matrix
  • Per key RGB reactive lighting
  • Powered by two Pro Micros
  • TMK on first Pro Micro, same firmware as the Gnap!
  • Arduino sketch running on second Pro Micro
  • 48 WS2812B LEDs
  • Matias click switches with clear body
  • 1.2mm PCB
  • 1.2mm top plate
  • 1.6mm bottom plate
  • 19.05mm switch spacing. Not compatible with the Planck
  • M2 11mm spacers
  • 0805 0.1 uf capacitors
Full RGB 48 key Alps ortholinear keyboard. This uses the same firmware as the Gnap! which uses the serial port to communicate with the second Pro Micro which is controlling the LEDs. Instead of a single color LED matrix on the Gnap!, the second controller is connected to a string of WS2812B LEDs.

The WS2812B LEDs fit snugly in the cutouts. Tiny solder bridges connect the LEDs to the PCB. 1.2mm PCB was used to make the bridging easier. With 1.6mm PCB the LED sits low in the cutout and the solder bridge was difficult to form. It works just like the 30% MX RGB board, but with Alps there is no center switch stem and the LED could be placed closer to the center of the switch.

The only problem in assembly is the sockets for the Pro Micros. The Alps switch is wider than an MX switch. The pins from the socket touch the edges of the switch. The pins need to be trimmed as short as possible and soldered as flush to the surface as possible. I also ground the edges of the switch down a little so that they would sit flat against the PCB over the pins.

Running the LEDs at 1/4 power it draws about 400mA in a full rainbow display. The Adafruit Neopixel library lets you set the maximum brightness. Potentially I could plug in both Pro Micro's at the same time to provide more double the current, though it is already quite bright at 1/4 power.

Currently deciding on revising the PCB with the Pro Micros rotated like on the Gnap!. This would remove the problem with the socket pins. Would have to either plug in from the side, or run a pigtail to a USB connector on the back like on the Gnap!.
One of the color patterns programmed in the the Pro Micro running an Arduino sketch. You can see more of them in the video at the bottom of the post.

The top PCB plate was originally green but I sanded it down to the bare FR4 material.

The schematic showing the switch matrix with the WS2812B LEDs integrated.

Front and back of the PCB. On the top you can see how the pins of the socket overlap the white outline of the switches.

Side view showing the two Pro Micros. The one on the left os running TMK, the one on the right is running the Arduino sketch.

11mm brass spacers.

The Pro Micro running TMK. You can see how the pins from the socket would interfere with the switch if they were not trimmed.

The Pro Micro running the RGB Arduino sketch.

Random LED output. There is also an interactive mode that lights up the switches as they are pressed and then fade. There are many WS2812B effects libraries for the Arduino.