Friday, July 24, 2020

penny pincher

Penny with penny spacers

The Penny is a 4x12 grid layout powered by a Pro Micro. Pennies were used as an alternative to the usual M2 spacers I use to assemble my keyboards. 1.5mm x 15mm slots were added to the perimeter and two in the middle.

Penny's are 19mm diameter and ~1.5mm thick. They fit a bit loose in the slots. Maybe mint condition penny's would be tighter.

18 cents installed in the bottom of the PCB. The Pro Micro is socketed and there is a place for a reset switch. The diodes are installed on the top side of the board. Cathodes to the square pad.

A second PCB is placed on top the main PCB. I have also used dimes and they work as well. You could also use washers in the right size. 17-19mm in diameter.

Rubber bands hold the two PCB together. These are #64 rubber bands that are 3.5" x 1/4". They aren't very tight. There are also #61 and #62 rubber bands that are 2" and 2.5" long. Those should hold more tightly.

On a flat surface it feels quite solid. PCB mount switches were used. This would also work with the 4x4 switch plates I used on the unquadquad if you needed to use plate mount switches. The switch footprint allows the switches to be oriented in any direction.

The PCB can be flipped. This shows PCB flipped and the Pro Micro installed on the opposite side. The firmware needs to have the order of the Column pins reversed if it is assembled this way. It shares the same matrix layout as the Gnap! and can run the same firmware.

Gerbers on git

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Tuesday, July 14, 2020


Germanium Diodes

I have a lot of NOS (New Old Stock) Russian germanium diodes that I purchased on eBay. I've used them in a few keyboards in place of the common 1N4148. They don't always fit as they are much larger.

I decided to make a board to highlight these large glass diodes.

The diodes are all moved to the top left of the board. In 4 clusters of 12. Each of the clusters is a row.

The board is a plain 4x12 grid layout. Powered by a Pro Micro. This one has the new Sparkfun Qwiic Pro Micro which has a USB-C connector.

I use a second PCB as the bottom. There are holes for M2 spacers and screws to hold the two PCBs together.

I installed Peel-A-Way sockets on the PCB. I did try installing them in the small top PCB as well but trying to get the leads to line up was next to impossible as the diodes would wobble in the sockets. Soldering them held them in place and made it much easier to fit all 13 pins in the socket.

The top PCB connects the Cathodes of the 12 diodes together. There is a 13th pin that connects the Cathodes back to the main PCB.

The WS2812B RGB LED is installed under the diodes. The dot indicates pin 1, which is the opposite corner of the notch on the LED.

Trimming the leads in a staircase pattern made it much easier to fit the top PCB. The leads were trimmed flush to the PCB and then soldered.

Here the bottom piece is the same PCB in black. I had already soldered a set with sockets before realizing how difficult it is to align all 12 diodes.

The grid of holes to the right of the Pro Micro are for small zip ties to secure the USB cable. I ran out of red ones, would use at least one more to secure the cable.

The matrix is identical to the Gnap. The WS2812B LEDs are connected to the same pin as on the Gnap RGB (Gnap with a WS2812B strip attached). The same firmware can be used, the only change needed is the number of RGB LEDs. 4 instead of 7.

I used the same 4x4 plate that I made for the unquadquad. The PCB also has the holes for PCB mount switches.

With some black keycaps.

Gerber files on git.