Electrical Gremlin - Actual Question

On the smallest mill I use regularly It has developed the habit of going into E-Stop when the coolant pump starts and stops. Its controlled by
an HH52P 24VDC coil relay. The same model relay is used to control the spindle on-off signal to the VFD.
All I use this machine for is engraving, but its still annoying. I have a simple work around. Start the coolant pump manually (on screen button), and if it trips the e-stop reset and start it again. Then begin code execution. To be honest its not that big of a deal. The shop is busy and I mostly just want to get parts out the door. Still I think it has to be a simple noise problem of some kind. Maybe an especially noisy arc when the relay actuates.
I'm going to try a new relay. These are probably the cheapest Chinese relays available. (I did have to replace the spindle start relay a couple years ago).
What do you think is most likely? Do you think there is a way to mitigate it? Maybe with a choke? Possibly a diode on the coil trigger input?
I think if it is the relay itself its most likely the primary contacts because it happens sometimes on both pump start and pump stop. Neither affects the machine position since both happen when the machine is momentarily stationary. Its just annoying.
It did not happen at all for the first several years I owned it, and it is the oldest CNC machine I use regularly. (almost everyday)
It is a Mach3 controlled machine using a Smoothstepper for the motion interface between the PC and the BOB. The wiring is pretty clean and orderly and I have checked every connection on the machine.
Other than being a cheap (relatively) Chinese cast iron dovetail mill, that like many I had to fix before it was passable to use, It really doesn't have any other problems. Before getting other newer machines I made a lot of molds with this little machine.
Well, now to order some more relays.
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On Sun, 19 Sep 2021 10:31:00 -0700

Do you have a flyback diode paralleling the relay coil? This explains it better than I can:
https://resources.altium.com/p/using-flyback-diodes-relays-prevents-electrical-noise-your-circuits
Also might want to search out snubber diode...
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Leon Fisk
Grand Rapids MI
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On 9/19/2021 2:21 PM, Leon Fisk wrote:

Bob, Just for some giggles!! Can you get access to the actual contacts. If Yes, the try a simple piece of folded sandpaper or abrasive strip. The attempt would be to just clean the contacts of some carbon.
If the relay is enclosed in a plastic cover maybe the cover can be popped off and the do the same as above.
I just had an intermittent issue with a door open relay. After replacing the relay and all worked as it should I took the cover off the relay and inspected the contacts with a microscope. To the naked eye there was no issue visable, however with the microscope I could see some etching of the contact surface. At that point it was not worth my time to clean it up and take it back to try to see if the customer gets re-irritated. :-)
Anyhow, for what you are doing it might be a quick fix and maybe a way to get convinced it really is the relay that is irritating you!!! :-)
Later,
Les
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On 9/19/2021 1:20 PM, ABLE1 wrote:















I've got a half dozen relays in the mail. I have three machines that use these same relays (different names and mfgs but the same basic relay) for a variety of switching and control. I figure it can't hurt to have some new in package on the shelf. If a new relay fixes the problem I probably won't worry about any further. This one worked great for several years. I may throw some noise cancelling component on the switched side if I remember. Its not like I don't have diodes and caps laying around... heck I though I had spares of this relay, but I must have used my last one on something. I do have an unused base. LOL.
I guess I could have swapped the spindle relay to test, but I'm just to darned busy these days.
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On 9/22/2021 3:40 PM, Bob La Londe wrote:



















Preliminary testings shows a new sub $5 relay did the trick. Ordered on Ebay shipped from Amazon. Maybe it was a sub $3 relay. LOL.
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On 9/22/2021 8:08 PM, Bob La Londe wrote:




















Congrats Bob!!
You know that given the same daily workload feels like a lot more as you age?? ;-) Or something like that!! LOL
Les
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On 9/22/2021 6:33 PM, ABLE1 wrote:






















Less feels like more.
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On 9/24/2021 11:11 AM, Bob La Londe wrote:






















Sooooo..... The new relay failed on the very first actual machine operation. Of course after I had a part loaded and indexed to engrave. I coated the part with cutting oil and engraved it anyway, but not a satisfactory solution.
I tried a couple other relays. Still nothing.
I started tracing things out. The relay is triggered by another relay on the BOB (break out board). It worked fine. The wiring was all intact. No mouse droppings. In connecting and disconnecting things I found a bad crimp in one of those stupid lugs required for European terminal connection. Still nothing. Then one of the mounting base screws would not tighten down. I replaced the mounting base, fixed the bad crimp (cut the lug off and threw it away), and it still wouldn't work. Then I put the original relay back in, and did a torture test of tapping rapidly with the mouse on the onscreen coolant button. Perhaps 100 cycles rapidly and the pump cycled on and off without issue and without putting the machine into E-stop.
Looks like maybe a combination of a bad crimp and a bad mounting block may have been causing the whole problem. The original relay is back in the machine.
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On Mon, 4 Oct 2021 10:52:25 -0700

Well... at least you didn't have to drive 100 miles in between attempts...
All that old security wiring experience paying dividends ;-)
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Leon Fisk
Grand Rapids MI
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On 10/4/2021 11:09 AM, Leon Fisk wrote:

LOL.
Sometimes more. I had a few outlying customers. Mostly because nobody else wanted to drive out to take care of them. One was 75 miles one way, and another 152 miles one way. I wonder who takes care of them now.
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"Bob La Londe" wrote in message ... Looks like maybe a combination of a bad crimp and a bad mounting block may have been causing the whole problem. The original relay is back in the machine.
--------------------
I've been using this for larger crimps for which I lack the proper tool: (Amazon.com product link shortened)
It may not be 'right' either, but it's versatile enough to progressively compress starter cable lugs and copper tubing into solid hex connections.
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"Bob La Londe" wrote in message
On the smallest mill I use regularly It has developed the habit of going into E-Stop when the coolant pump starts and stops. Its controlled by an HH52P 24VDC coil relay. The same model relay is used to control the spindle on-off signal to the VFD.
-----------------------
That relay is rated to switch only 5A. What is the pump motor starting surge?
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replying to Jim Wilkins, 42 electrician wrote: the tripping is most often an electrical overload detection function. disconnect the motor and hit the relay. if you dont trip then the motor is the pig- not the relay. the relay inrush in open-magnetic circuit state is probably MUCH lower than the motor inrush when the contact closes but the machine probably isnt calibrated to know the difference since they are milliseconds apart:::: find the piggy, fix him, it may NOT be the place where you hear him squeal
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replying to Jim Wilkins, 42 electrician wrote: the tripping is most often an electrical overload detection function. disconnect the motor and hit the relay. if you dont trip then the motor is the pig- not the relay. the relay inrush in open-magnetic circuit state is probably MUCH lower than the motor inrush when the contact closes but the machine probably isnt calibrated to know the difference since they are milliseconds apart:::: find the piggy, fix him, it may NOT be the place where you hear him squeal
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