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Topic: Arduino has some strange reactions (Read 4 times) previous topic - next topic

kf2qd

It would look  like you need to get some RC suppressors for the AC Relays. Whenever you switch off a coil you get are probably goint to get some noise - might get lucky and switch at zero crossing but...

They make RC suppressors that you can get from an industrial suppliers. Check for an Allen-Bradley distributor.

Another possible method is to put some ferite beads on the lines running to the Arduino board. ou are getting induced voltage spikes that are affecting the low voltage side of your control box.

cncb


The way the Pi circuit is shown here.
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html
The inductor is in series with the supply with a capacitor to ground on each side of the inductor.


Thanks for link and info. You mentioned to use a choke on "either side", what did you mean by that? The schematic on that page shows a choke/inductor wired in series with the + side of the supply to the IC, after the cap. Perhaps you meant on the +5VDC out to the relay board as well.

For the relay board, I take it that it would be best to put this at the input terminals, rather than on the arduino output since there is a decent separation of those points in wire length.

I tried even a preliminary try with a 100uF cap that I had with no noticeable difference yet. I will have to buy some different size chokes to try.


cncb


It would look  like you need to get some RC suppressors for the AC Relays. Whenever you switch off a coil you get are probably goint to get some noise - might get lucky and switch at zero crossing but...

They make RC suppressors that you can get from an industrial suppliers. Check for an Allen-Bradley distributor.

Another possible method is to put some ferite beads on the lines running to the Arduino board. ou are getting induced voltage spikes that are affecting the low voltage side of your control box.


Thank you for the advice. Perhaps that is what happening and why it is a bit random, depending on where it is switched. In regards to the RC suppressor I will investigate it more. I found a good writeup by S+S, http://www.sprecherschuh.com/library/techdocs/get/TECH_Surge_Suppression_109.pdf

I doubt that I will get this accessory for my contactor, as it isn't as high end as the S+S but I could try to replicate it with individual components.

My contactor is a 24VAC coil.

Grumpy_Mike

Quote
You mentioned to use a choke on "either side", what did you mean by that?

No it was a capacitor on each side of the choke.

The other advice I have given you before is to use a snubber circuit. That is what cncb is saying.

cncb

So I did some more testing and tried a few things. I have to buy some ferrite beads/chokes to play with, but I still wanted to isolate the power sources. This time I took it a step further, which I've detailed below.

1. The most apparent problems occur when the solenoid is switched off, however the contactor has some less noticeable issues.

2. Sometimes the AC contactor with no load, being switched "off" resets the arduino or ripples the DC supply enough to reset it. This isn't noticable by eye but by the way it reacts, it drops all outputs in a way (in my limited experience with the arduino) that could only be done by a reset, and prints the serial in a way that could only be done by reset.

3. Simple DC/AC Relay switching causes no apparent problems. (IE: Switch + Relay Board + Relay, no Load)

4. I tried adding an addon Contactor RC Snubber to the coil, no #2 problems with it installed, same as simple LL, LV operation. No resets apparent at all and no half flashes of LEDs on the relay board, it seems perfect.

5. Keeping the RC snubber in, and powering the dc bus from a bench supply on House Circuit 1, AC Transformer on House Circuit 2, and the rest of the power for the box on House Circuit 3, the problems are just as apparent if not worse than before. Sometimes causing up to 3 cycles on the solenoid inadvertently until it appears the arduino gets enough ripple to reset itself and de-energize the outputs, so to speak.

Any ideas on how this tiny AC solenoid load is causing these problems? Even being isolated on completely different circuits? I'm confident that the RC snubber has alleviated the problems on that side, and I even put a considerably larger inductive motor load on the contactor and it works flawlessly. Everything leads back to these darn solenoid valves! I will try the decoupling circuit when I get some of those components in from mouser.

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