After the more or less functional Arduino workstation the ModLab has a new slogan:

Overengineered at its best!

Why? I want to improve the overall quality by using more additional circuitry as well as safety circuits. Emergency stop system? Of course! Every metal part connected to PE? A must have! Expensive TVS diodes everywhere? Hell yeah!

And so on… I think you get the idea. So at first I’ll start planning.

The rack is the base

I don’t know if you know, but i LOVE racks. So everything will be rack-mounted. Why? It looks awesome, is rigid and modular. On IT-Budget i found an inexpensive 19″-Rack with 24Us which is perfect. So I started up Excel and made a table on how I wanna fill up the rack. After many reviews it looked like this:

Sowwy, still German… working on it…

As you can see, the FMAS has the lower 6Us in thwo racks at 3U each. Directly above is a rack floor for cable management etc. Cable canals and DIN rails for all the electrical stuff followed by a control panel for power enabling. There will be a PNOZ for emergency stop system, fuses, relais etc. Lots of wiring work.

In the upper 9Us there will be the ModLab.

If finished, pictures of the assembly will follor


The inner workings and the bus

Now we will concentrate on the modules and de backplane bus. I wanted to take things more serious and make a list with modules i want to make. So now there will be the standard ideas (power supplies, waveform generators etc.) as well as more complicated ones (logic analyzers, logic sense probes, logic testers, frequency counters etc…).

The most difficult decision was to choose a controller for the mainboard unit, the so called Host Bus Controller (HBC). The current plan is to use a STM32-NUCLEO board as main processing unit. It will control a 7″ TFT display with touch and manage all the bus lines on the backplane. But I never worked with STM32s, so it might take a while ;). For the HBC there might be a few different versions until I finally combined all hardware and software.

The reason why I won’t use an Arduino is simply that the bigges Arduino (Arduino DUE) has too few IOs and is a bit too slow. I knew what i wanted on the bus, so here we go.

I will use DIN 41612 C 64pin connectors as normal for 19″-modules. Since i want to make some bigger power supplies I had to reserve enough pins for the power rails and every other pin is used for signals. I wanted to implement an 8bit parallel bus as well for rapid mass transfer of data (up to 10 Mbit/s). The parallel bus will use hardware handshaking for transfer protocol. Also on the bus there will bi RS232, I2C and SPI as well as two DACs for sound signals.

The current bus pinout looks like this:


Electrical stuff

After I knew what i need, i could work on the electrical wirings for the rack. But first I needed to make a wiring plan. Since I had to work with switches, relais and fuses and of course the full 230V, I couldn’t simply draw something and hope for the best. The wiring plan had to look tidy and should help me wiring up everything.

Coincidently I just found a nice litte program called QElectroTech, which is freeware and can do the same as EPLAN. The program was a blessing and worked like a charm.

After several days of planning and drawing, reviewing and drawing everything again, I finished the plan. While buying all the parts, some things changed a little, but here is the finished plan after correcting every change:

Page 1: Power inlet and emergency stop
Page 2: power supply FMAS
Page 3: power supply ModLab

As you can see, planning is key in this project and not the fast result. Also I want to assure some kind of quality and longevity. Also I wanted to learn about quality management.

That’s it for now, I will keep you updated of the progress I make.

If you have ideas for modules, please contact me 😉