April 2, 2020 / News
Deploying a Raspberry Pi Prototype Straight to Industry
Why is Raspberry Pi so popular with engineers?
The availability of fantastic open source software makes
Raspberry Pi special. Selling over 30 million units worldwide, Pi has become so
much more than the educational tool intended to get school aged kids interested
in computer science. In a world dominated by massive data centres and
cloud-based applications, engineers love the low-cost computer for the
accessibility it affords to IIoT projects.
After completing and validating an industrial Pi prototype,
engineers are faced with a decision; switch to a platform created specifically
for the rigours of the factory floor and risk increasing the cost and time to
market, or gamble with deploying the prototype.
Can Pi connect to industrial sensors?
Sensors, typically requiring 12-24V power and signalling
changes using the same voltage, are essential to any industrial application
that requires automated control. Raspberry Pi’s GPIO input circuitry can be
driven to either 3.3V (high) or 0V (low). So, whilst a 12V industrial 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.
Connecting a sensor to Raspberry Pi directly often means
stripping the sensor’s 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’s 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.
Can industrial EMI cause problems for a Pi prototype?
Industrial environments are often loud, but it’s the silent noise – the electronic interference – that can damage the performance of sensors and communications systems or stop them from functioning altogether.
There are varied solutions for EMI management – increasing the distance between the source and the susceptible device, rerouting cables, even experimenting with the orientation of devices can limit problems. However, particularly in an environment with many potential sources of interference, the best solution is to ensure equipment is designed to minimize emissions and be less vulnerable to external EMI.
How hot is too hot for Pi in industry?
To keep costs low, the Raspberry Pi is built with
commercial-grade chips which are qualified to different temperature ranges; the
Microchip LAN7515 is qualified from 0°C to 70°C. The SoC (System on Chip – the
integrated circuit that does the Pi’s processing, a Broadcom BCM2837B0) is
qualified from -40°C to 85°C.
In some tests, the Pi’s SoC has been shown to exceed 100oC,
when pushed beyond its qualified operating temperature range its long-term
performance is not guaranteed.
Fortunately, any solution that decreases the effect of high
temperatures, such as moving Pi into an upright orientation, adding an external
fan, or employing a heat-sink, can help keep Pi’s SoC under the soft limit.
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What are the industrial power considerations?
Raspberry Pi is powered by a very specific +5.1V and 2.5Amps
supply – the majority of factories with have power supplies of 12/24 VDC.
Alongside this mis-match of input supplies, in a factory where a common
attempted fix for a malfunctioning machine might be to pull the power rather
than diagnose the root cause, the resulting memory corruption issues can cause
expensive downtime.
How does Brainboxes BB-400 industrialise Pi for the
factory floor?
Brainboxes BB-400 Industrial Edge Controller
equips Pi with
hardware fit for purpose,
an industrial Raspberry Pi
that eliminates the need
to gamble
with a system that doesn’t meet specs.
• 8 Digital IO lines – 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.
• Embedded numbered terminal
blocks – no soldering to create secure connections allowing
multiple reconfigurations. It’s a lot easier to decipher correct connections
when you don’t have to count down a row of tiny header pins!
• Fully EMC compliant
– the BB-400 doesn’t emit significant amounts of EMI, and crucially for
industrial applications, continues to function as intended in the presence of
machines and devices that do.
• Custom aluminium heatsink – maximised surface area to utilise thermal conduction and
draw heat away from the processor.
• 5-30 VDC power supply – wide
voltage input matches
industrial power supplies.
• UPS power management – Dual
redundant supply means that if one power supply fails, the other will take over
straight away reducing the risk of memory corruption. On board super
capacitors offer clean shutdown if power is interrupted, and an onboard log to document
exactly when power failure occurred.
