Designing and building a Arduino based 6 Channel Loop selector. (PPS-6 Working title)

Hello everyone.

So I've been putting it off for a long time but I've finally gotten round to doing some more work on my new second generation loop selector. This time I've gone for 6 channels (PCB supports 8) as that is about the maximum I can comfortably cram into a 1032L enclosure.

I drew up the schematic and board in EAGLE quite some time ago. It uses an Arduino Nano which is mounted on the PCB. For the Loops I have used A5W-K relays for true bypass. These are switched by a ULN2803 driver chip which is controlled from a 74HC595N Shift register IC. The LEDs are controlled by a 16 channel PWM LED driver a TLC5940. Any spare pins I had on the Arduino I used for inputs from the foot switches. I have since changed my design and my future version will just use 74HC595N ICs so I can use more pins for more inputs a the TLC5940 takes up 5 pins.

The schematic I have drawn is just stuff I have taken from the internet and the datasheets of the ICs

The TBx6+2 Schematic

I managed to fit all the components and 6/8 relays on the PCB which measures 100mm x 41mm

PCB Layout

 I then panalized this layout to get 2 boards on a 100mm x 100mm panel. I ordered the PCBs through DirtyPCBs and I was very happy with turnaround time and outcome. Highly recommend using them. I've just done a huge order of 450+ PCBs and they have just landed in the country. I'll do another blogpost explaining how I used panalization to get some many boards onto 1 panel after they arrive in.

1 PCB ready to go

I proceeded to part the board out and make a few testing rigs for programming and testing functionality

 

Now that the boards were ready I had to write the Arduino sketch. I'm super novice at this but luckily I have a friend that can do this stuff in his sleep. So I did as much as I could and only asked him if I was desperate. I ended up using a bunch of great libraries to help me with my sketch.
The One-Button Library. The Shifter Library. The TLC5940 Library. Without these I would have been lost. I have the sketch at a stage where I'm almost happy with it.

Here is a little video of the operation.

Needs some work but It's ready to box and refine. So now to the box.

I think everything will fit well. So I decided to head over to TinkerCAD and make up a 3d model to see if it all fits.

Looks like it all fits and off to making a drilling template. Drill, Powdercoat, Decals, Clear, Assemble

Next post.