Cold weather affecting proximity sensors?


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  1. #1
    Activation process justicedavid65's Avatar
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    Default Cold weather affecting proximity sensors?

    I built a 5' x 5' ball screw machine about 9 months ago and all has been working well, but the last few day when I first start it up I get sensor trip errors. I have to turn it on and off a few times before it starts working without the errors. After this is works fine all day. Could the cold be affecting the sensors? I live in NC and it's cold overnight (30's), but warms up throughout the day into the 50's or 60's usually.

    Thanks,

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    Member john-100's Avatar
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    Default Re: Cold weather affecting proximity sensors?

    yes the cold could effect the sensors

    what is the sensors part number ?

    If its from Honeywell or Allegro Micro Electronics you may be able to get a detailed data sheet
    to know how changes in temperature affects the sensors switching characteristics

    Also the machines axis will be less free running , changing the position the axis stops once the sensor is triggered

    John



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    Default Re: Cold weather affecting proximity sensors?

    Most certainly temperature impacts electronic but 30°F really isn’t that cold. Have you narrowed this glitch down to one axis or switch? My thought here is that one switch might be flaky and extremely temperature sensitive. It is not unusual to have one bad Apple that exhibits bad behavior.

    As John suggest above a data sheet will tell you if you are operating within the switches rated temperature range! Also don’t dismiss other devices causing issues like this a flaky power supply can cause issues.



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    Activation process justicedavid65's Avatar
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    Default Re: Cold weather affecting proximity sensors?

    Thanks guys, It was around 50 this morning and it was working fine. I think it's definitely the cold. It's only going to get colder though. Going to have to do something about it.



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    Default Re: Cold weather affecting proximity sensors?

    I'm just guessing, but perhaps there's a crack in the sensor somewhere (PCB, coil, etc) and when it's cold it shrinks just enough to cause a problem?



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    Default Re: Cold weather affecting proximity sensors?

    I would not consider 30°f cold, not here at any rate.
    Many of the prox sensors I use are rated much lower than that, for e.g. the Omron style are rated to -40°c = to -40°F.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    Default Re: Cold weather affecting proximity sensors?

    Quote Originally Posted by justicedavid65 View Post
    Thanks guys, It was around 50 this morning and it was working fine. I think it's definitely the cold. It's only going to get colder though. Going to have to do something about it.
    This might not be much fun when it comes to finding the root cause. There are a few things worth trying that are not too expensive.

    The first thing to try is cooling suspected components with a component freeze spray or canned air. Do one suspected component at a time. I kinda doubt the issue is a prox switch but if you suspect so start there.

    Second; this is something I forgot to mention in the first response but electrical connections are always suspect. Plug and socket connectors are one consideration. Cold solder joints are another. Bad connections are about 80% of all electronics problems.

    Wires running in drag chains or otherwise flexing a lot are suspect. Usually you don’t see these failures as thermal issues.

    A fourth consideration is divide and conquer. Assuming your electrical panel is oriented so that it is possible put a small heater in the panel to warm it up before starting. This could cut your search area in half if the problem goes away. You could also do the opposite and heat up suspected bad prox switches when the machine acts up. This effectively lets the weather freeze the electronics then you selectively heat things up to isolate the issue.

    Just some ideas off the top of my head! These sorts of intermittent issues are a real pain in the behind. I just spent a couple of weeks on a robot extractor to clear up many intermittent issues. This involved wire harness replacement, Mate-N-Lok electrical connector replacement, prox switch replacement and other issues, in different parts of the machine. Frankly it can be frustrating work.



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    Member htrantx's Avatar
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    Default Re: Cold weather affecting proximity sensors?

    More often than not you have EMI problem, which worsens at low temperature. This is due to the higher currents of motors and other like VFD. In addition, the input trip point of electronic components are shifting with temperature and reducing the operation margin.

    I would redo/improve the grounding/shielding of the cables, and/or improve the filtering of sensor signals to the controller.

    Last edited by htrantx; 11-23-2019 at 01:25 PM.


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    Default Re: Cold weather affecting proximity sensors?

    To anyone still following this, it gets weirder. I spent a day with the machine down and just checking anything I could think of and many of the suggestions(thanks!). Nothing really seemed to be wrong? Then by just a stroke of luck I noticed something. When I start the machine for the day, I always home, which is the back right corner. Then I move it to the front left corner where the laptop is, and where I stand to start jobs. I always use the diagonal move button at 500mm. This will move it right where I want it in 2 clicks. I noticed that this is where I get the sensor trip error, so I wondered why it would home just fine, but then give me an error when I tried to move.

    So, I yesterday I tried using the X and Y buttons to get it to the front and this worked just fine. For some reason when I use any of the diagonal buttons I get this sensor error?
    I have been using the machine for 2 days now and it's working great as long as I don't try to move the machine using the diagonal move buttons?



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    Default Re: Cold weather affecting proximity sensors?

    I’d try different simultaneous axis moves. You might be seeing dips in power supply voltage. That is one disadvantage of running motors off the same supply as the rest of the electronics.

    Another possibility is increased noise. A small cap across the switch inputs might help.



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