MM-PLC featuring picomite

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Joined: 05/03/2018
Location: Netherlands
Posts: 3791
Posted: 02:42pm 03 Dec 2021      

In my job I often need to improvise a test setup, to quickly prove or debug new designs. Many of those test setups make use of an Arduino as either a controller, or a PC IO device. Switching relays, reading in signals, sometimes measuring.

These arduino's run a version of tinybasic, limited to the RAM of the Arduino.

I often wanted to switch to MMBasic, since it is so much more powerfull, but the mites need to connect to my peripherals. I tried to order a duinomite, so I could plug in my relay cards and opto inputs... But they where out of stack at that time.

With the rise of the picomite, the idea using MMBasic in my test setups revived, and I decided make a plan.

First I wrote down what I have common in most setups, and what is optional, and nice to have.
Common was 1 or 2 relays that can switch 10A and 250V(ac or dc)
Common was that I need minimal 2 sometimes 4 digital inputs (isolated). Logic level, or 24V or 250Vac.

Optional where I2C expansions, incidental SPI, PWM's, or more logic inputs.

The Common items are included in MM-PLC, the optional items can be added via a 20pin ribbon cable, and mounted in a similar box.

The Common module fits in a DIN rail housing and consists of 4 boards
1/ The picomite
2/ The IO board (relays / optocouplers)
3/ The power supply (generate 5V from 7V....32V)
4/ The interface/LED board

Following pictures show how the puzzle is put together, and the stack of boards fit's in a DIN rail housing. The housing still needs some holes drilled (USB for the picomite, LED's). When that is finished and labels are made I will post more pictures. This is the status today, everything has been checked and is working.

It took quite a lot of time to design (in my mind) the 3D puzzle to fit all in this small housing. That was the challenge I put myself.

Would I do it again ? No, probably not. Once this is put together it is nice and compact, but hard to repair if something broke. Next time I would simply take a big (eurocard) board and put it all on that card. And use a bigger box.....