Industrial Automation Card for Raspberry Pi

In September 2017, we launched the MEGA-IO Expansion Card for Raspberry Pi. We crammed eight relays, eight 12-bit ADC channels, 12-bit DAC, eight opto-isolated inputs, four open collector outputs, and six GPIO's into the same form factor with Raspberry Pi. The project was funded and is available now on our website for direct purchase.

The main target of the Mega-IO card is home automation by DIY users. The Mega-IO industrial version (MegaIO-IND) brings a low-cost solution to the control of industrial processes.

MegaIO-Industrial Specifications

• 24VDC power supply

• Four optically-isolated 4-20mA inputs

• Four 4-20mA outputs

• Four 0-10V analog inputs

• Four 0-10V analog outputs

• Four optically-isolated digital inputs

• Four optically-isolated open drain outputs

• Four optically-isolated 10A/250V relays with status LEDs

• Four General Purpose LEDs

• RS485, CAN, 1 Wire communication

• Real-time clock with battery back-up

• Configurable interrupts

The Raspberry Pi expansion connector is passed through and can be used to access all the GPIO pins, or to install any third party add-on card. Up to four MegaIO-Industrial cards cand be stacked on top of each other. Any number of cards can be controlled from a single Raspberry Pi using the RS485 port.

MegaIO-Industrial Block Diagram

Board Layout

High Voltage Area

In order to switch 250V and 10A, we extended the short side of the board outside the Raspberry Pi area, and separated all the high voltage runs from the low level digital.

The high voltage area of the board will be isolated with a fiberglass shield (not shown in the picture) mounted on the bottom corner holes

DC to DC converters are used for power and ground separation between the two areas. Optical isolators provide digital signal separation, and a physical cutout gap assures high voltage separation.

The trace thickness and spacing is calculated according to the IPC-2221B for 250V and 10A.

Linearity

To check the linearity of the card we used a four digit Fluke 28 II. After calibrating the end points, the worst case linearity is 0.2% for all current I/Os and 0.15% for voltage I/Os.

User's Guide

User's Guide is available for download from our website.

Software

All the features of the MEGAIO-IND card are accessible from a command line interface which can be downloaded from GitHub. Python drivers are available as well.

CODESYS Drivers

We provide drivers for CODESYS, "the leading hardware independent IEC 61131-3 development system under Windows for programming and creating controller applications." A demo project shows how to read any input and control any output, either from a stand-alone windows application or from the browser.

Self-Testing

Command-line functions are available for self-testing all inputs and outputs using external jumpers. Jumper any 0-10V input to and 0-10V output, any 4-20mA to any 4-20mA output, any opto-isolated input to any open-drain output and run a command to test both I/Os.

MegaIO-Industrial Application: PID Controller

Here is a simple (and useless) application: balance a ball in a tube.

Please visit: https://www.kickstarter.com/projects/279405789/megaio-ind-industrial-and-building-automation-for