This is what i call my "µPLC". It's a pcb for a 40 pin dip PIC, with programmer header, buttons, (external) pull up resistors, dip switches, led's, I/O connectors, LM35 analog temperature sensor, place for a 16*2 lcd interface, 7805 psu... It has the capability of using the B and D port with an ULN 2803. One of these ULN2803 can drive relay's on a relay card that connects trough a header...
I use it for my model train layout to control things without the need to design specific hardware (just like a real PLC, but with a microcontroller). Just connect everything to it, write software for the PIC and it does what it needs to do.
Now i want to design V2.0:
Things that need improvement:
1)The 2 ULN2803 chips have their own connector, but the I/O ports on the µC to drive these ULN2803 have their own connector, so i can use them as GPIO to. (the connecter at the top connects to portb, while the connecter at the upper right corner, is also connected to port B, with the ULN 2803). Is there a simple and cheap way to "merge" these so i can save space on the pcb for other things? (Open collector outputs with the ULN driver, and GPIO on the same connector?)
2)There is a 16 characters *2 lines HD44780 LCD interface on the board, but it is not my intention to mount it directly on this pcb. I want to mount this lcd on a front panel or something like that, and need a better interface connector. Any suggestions for this one?
3)I learned to program microcontrollers at school using flowcode and the formula flowcode buggy. Now i use JAL and C to do that. To program the pic on the buggy, i did'nt use a programmer like my pickit 2. How is this possible? Can i add that functionality to my board?
4) I hope nr1 here is possible so i can add other connectors on the pcb. (for Loconet, USB) and other capabilities, but i want to keep the board size the same or smaller...
5)maybe i replace the 7805 with MC 34063? Certainly, I need a better connector for the "power". No i use these Wago lever clamp connectors for everything...
6)any suggestions? Questions? Shoot!