Old school programmable switch pack

[dbuckley]

Course one can multiplex the I/O, but it's more work. In the specific case of my Swiss Army knife board, as the relay outputs are driven by a ULN2003, going from "eight relay drive outputs" to "more than eight really drive outputs" is messy, which indicates that it probably isn't the right solution. At relatively low numbers of I/O, just interfacing directly to the chip I/O is an easy solution.

 

If I had to build on of these without getting into a custom board spin, I'd build a ratsnest assembly: Start by adding up the I/O:

 

The spec says: 12 channel select switches, a record button and one each of a forward and backward button. Probably need a clear button as well.

 

16 buttons and switches with pullups soldered directly to the switches

12 outputs going to logic driven relay boards from Ali

 

So minimum 28 I/O. That I/O in Arduino or Arduino-like form: I'd go for the Teensy++ which has enough I/O, enough ram and codespace to get the job done, and 4K of EEPROM to store the entered patterns.

 

Missing from the spec was the rated switching voltage and current; the Ali relay boards are only fitted with little relays, so if it's big loads then a second layer of bigger relays might be a smart move.

 

As a one-off, this would give a workable solution, trading quality of product design for off-the-shelf-full-ness. If I needed to build a few of them, then I'd spin a board, no question :)

[alistermorton]

Fair comment, and you're right, for this sort of project the teensy++ looks well suited.

[boatman]

The Teensy++ 2.0 is also available in the UK (except that there's no stock!):

 

https://www.proto-pic.co.uk/teensy-20.html

[themadhippy]

Arduino mega,54 I/o's around a tenner for a "compatible" board off the bay