@ Sairus - I have not been able to sleep, tonight, so I have worked on your design. I have made the first draft of the Eagle schematic and board layouts. I have attached jpeg images for you to review. If you see needed corrections, let me know and I will fix any issues. (I already see that I left the capacitor values off of the schematic. I will correct this.) When you have given your final approval, I will post the Eagle files and pdfs, as I did for Jadew.
I determined that my confusion over the PL2313 being on the board was from not understanding that the UART-USB box on the schematic was just to represent this off-board component. I was further confused by the big capacitor, below the PIC12F683 in the photograph; I thought it was the PL2313.
Once I had this straightened out in my mind, I was able to follow your board layout. You came up with an elegant design and did well with avoiding cutting off access to ground.
There are a few minor differences to my representation of your work:
- You used 5mm holes for the IR components; I used 4mm holes. This is from the early design work of others, who determined that the smaller holes made a nice seat for the convex lenses and kept these lenses from being able to be scratched by the DMM lens. The smaller hole also helps prevent seepage, when potting the components in epoxy. However, if you would rather have 5mm holes, I would be glad to change them.
- All resistors and capacitor footprints are SMD 1206. (If you specified SMD IR components, your design could be fully SMD. This would reduce the interface profile. That would be very cool.)
- Please confirm that the value for the resistor for the phototransistor is 200K.
I am enjoying working with you, very much; you have excellent skills. It is great to be making another friend on the other side of the world. Hurray for the internet!
EDIT: You might want to swap the location of C1 and C2, to place the smaller cap closer to the chip pin. Also, I had made other minor changes to your board, that I forgot to mention... I added an independent ground pad, whereas you had attached the ground wire to a cap ground pin. And, I put both caps at the top of the board. This placed the cap that was below the chip a little closer to the pin, decreased the distance between the voltage coming onto the board and then being smoothed and removed a trace from underneath the chip, improving noise considerations. I have already added the cap values to the schematic.