Connecting a Raspberry Pi to Industrial Sensors

Sensors and actuators are essential elements of industrial systems, instrumental to any application that requires automated control.

Raspberry Pi provides general purpose header pins that can be connected to sensors, making the low-cost board a popular choice for engineering prototypes. Pi’s GPIO pins are designed for driving low current devices such as LEDs however, so is it possible to connect to the I/O necessary for industrial environments?

Industrial sensors typically require 12-24V power and signal changes using the same voltage. Raspberry Pi’s GPIO input circuitry can be driven to either 3.3V or 0V. This means that whilst a 12V water flow sensor might initially work hooked up straight to a Raspberry Pi, in long-term projects the incompatibility of the currents will almost certainly cause problems.

Does this mean your Pi can’t be connected to industrial sensors beyond a prototype?

Connecting a sensor to Raspberry Pi directly often means stripping wiring and soldering the cable to the correct GPIO pin. The 12 or 24V of an industrial sensor will then be driven straight to the Pi with nothing in the way to protect Pi internal circuitry including the processor. By adding extra circuitry as a buffer between the input pin and the Pi, it is possible to extend the processor’s source/ sink current capabilities, and prevent excessive power dissipation in the chip.

Brainboxes BB-400 is a smart controller based around an industrial Raspberry Pi and allows prototypes to be deployed straight into factory environments. Sensors and actuators are not wired directly to the Pi, rather electronics between the input pin and the chip do the work which prevents industrial voltages damaging the Pi.

As the BB-400 has removable terminal blocks the module can be taken out without affecting any of the pre-wired terminals. As a single misplaced component leg can cause the whole circuit to malfunction, another useful feature of the terminal blocks is their numbering; it’s a lot easier to find correct connections when you don’t have to count down a row of tiny header pins.

The BB-400 has 8 digital I/O connections, making it usable straight out of the box without the need for any add-on units, although there are a variety available if you do find you need more inputs and outputs. As it is packaged in a DIN rail enclosure, it’s the perfect solution for deploying a Raspberry Pi prototype straight onto the factory floor.

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Automation Update