I have built a 240 V 30 Amp brew control panel using PIDS to control the two heat elements (5750 W each) and want to monitor some things with the addition of an Arduino Uno. I want to place the Arduino inside the control box but am concerned about the proximity to the high voltage and amps pumping through the 10 gauge wires that will be perhaps within a 1/2 inch of the Arduino. Is there a problem with this? Will the proximity to high energy cause problems for the Arduino to function properly and safely? Thanks!
mikehoover:
I have built a 240 V 30 Amp brew control panel using PIDS to control the two heat elements (5750 W each) and want to monitor some things with the addition of an Arduino Uno. I want to place the Arduino inside the control box but am concerned about the proximity to the high voltage and amps pumping through the 10 gauge wires that will be perhaps within a 1/2 inch of the Arduino. Is there a problem with this? Will the proximity to high energy cause problems for the Arduino to function properly and safely? Thanks!
All depends. Did a licensed electrician install all the 240 volt wiring and was it inspected by a local authority? If yes to either, then you will be in trouble with both entities.
IF you did it all yourself, then there is no good reason to try what you are suggesting and see if there are problems.
Paul
Your concern is good, you are on the right side of this one. If you are under a code restriction, most areas in the US are, contact your local inspector and see what he/she wants, if you follow that you should pass inspection without a problem. I would expect problems, include information on the contactor (high voltage switch). Post your schematic, not a frizzy thing. Also how did you shield the low voltage Arduino from the high voltage, this is a code requirement.
I want to place the Arduino inside the control box but am concerned about the proximity to the high voltage and amps pumping through the 10 gauge wires that will be perhaps within a 1/2 inch of the Arduino.
Assuming it's all wired to applicable safety standards, just being within 1/2 inch of high energy cables won't cause issues ... its the switching of inductive loads, relay contact arcing and not using opto isolation, snubbers or MOVs for ARC/EMI/RFI suppression that can latch up an MCU. However, your load is mainly resistive, and I presume you're using zero-crossing type SSRs for switching the load.
- Avoid having high energy / high voltage conductors crossing over or under the low voltage PCB.
- Enable pullup resistors for all unused pins on your Arduino.
mikehoover:
I have built a 240 V 30 Amp brew control panel using PIDS to control the two heat elements (5750 W each) and want to monitor some things with the addition of an Arduino Uno. I want to place the Arduino inside the control box but am concerned about the proximity to the high voltage and amps pumping through the 10 gauge wires that will be perhaps within a 1/2 inch of the Arduino. Is there a problem with this? Will the proximity to high energy cause problems for the Arduino to function properly and safely? Thanks!
I'd go for full EMI screening. The Arduino should be inside a grounded die-cast box or similar, and all the signal
wires and power wires to it need decoupling to ground at RF (1nF--10nF ceramic caps to ground as
the wires enter (feed-through caps are best, though hard to find alas). Ferrite toroids are also useful
If there are very high currents upgrade that diecast box to a steel box to screen the magnetic fields better.
In the absence of such a full Faraday-screen approach, site the Arduino outside the control panel and still
block the RF with caps. This is an easier way to go as you won't be near the mains when you are testing,
and you won't be cramped inside the panel.
The fact the load is resistive isn't a panacea, mains switching involves massively high dV/dt
values (measured in GV/s) - that's easily able to capacitive couple into logic circuitry from
some distance. And wiring has inductance anyway, on a sub-microsecond timescale this will
actually dominate.
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