Ohmic trouble

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Likes
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Ohmic trouble

Post by Likes » Thu May 02, 2019 9:36 am

Okay- let me start by saying I bought my candcnc full automation bundle last July. The ohmic has worked intermittently, but has seemed to stop lately.As I understand it’s just a continuity tester to sense the top of the plate. Here is where my issue is.

If I unplug the “tip” and “plate” plug and directly short the terminals- sense lights up. If I plug it back in, the torch is raised, and I take a wire from the “plate” side to the tip of the torch, sense lights up.

I do nothing more than drop the torch to the top of the material, and the light goes out. I’m still effectively shorting the terminals out, but it won’t light as long as the torch is touching material. I need help- and fast please!

I called CandCNC and all the person said was I’m losing continuity. That just doesn’t make sense because the terminals are still shorted, so I should still have continuity. I have checked actual continuity and there is no issue. Just when it runs through the z-axis board it seems like.

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Re: Ohmic trouble

Post by Likes » Thu May 02, 2019 9:41 am

I’ve shorted the terminals together, and as soon as it touches anywhere on the main frame, the light goes out.

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WyoGreen
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Re: Ohmic trouble

Post by WyoGreen » Thu May 02, 2019 11:03 am

I've been pondering the problem you've been having. It almost sounds like either something is overriding the continuity, or the capacitance of the table is hosing things up somehow. Maybe you could take a regular volt/ohm meter and substitute it for the sensor. In other words, set the meter for ohms, and put one lead where the plate lead of the sensor is tied, and put the other lead on the plate. You should get pretty close to 0 ohms on the meter. You might also set the meter for volts to see if there may be voltage running around on the plate messing things up. At any rate, your results might give us a place to start trouble shooting.

Steve
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Re: Ohmic trouble

Post by Likes » Thu May 02, 2019 1:17 pm

Well... I was tinkering with it and the only way to get it to sense was by unplugging the float limit switch in the z-axis and by also unplugging the red wire from the I/O board. Now it works great...

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SegoMan DeSigns
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Re: Ohmic trouble

Post by SegoMan DeSigns » Thu May 02, 2019 2:54 pm

Electrical connections in the dirty plaz environment is always fun to trouble shoot. I clean all connections with contact cleaner then apply a die electric silicone prior to final assembly. I do this and other preventive maintenance twice a yr.

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Re: Ohmic trouble

Post by Likes » Thu May 02, 2019 10:51 pm

None of the switches or connections were dirty. The only thing I can think of (and haven’t confirmed yet) is I reversed the float switch from NC to NO, and when this circuit is active it somehow directly grounds or shorts the Sense circuit. It doesn’t make sense as to why the sense circuit would work up until I introduced the material or gantry or frame. For now I’ve unplugged the switch and am relying on the magnetic break away to estop the machine. Maybe I’ll tinker with it when I have some time and diagnose the issue further.

CGT80
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Re: Ohmic trouble

Post by CGT80 » Fri May 03, 2019 7:38 pm

I tried running the ohmic sensor but it was nothing but trouble with having water on the plate from cutting. It has been a while, but I recall having to do away with the z switch to run ohmic and when I removed the ohmic, I had to hook the z back up. Double check the directions for installation of the ohmic and see if it says to rewire the z switch or to remove it all together.

tcaudle
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Re: Ohmic trouble

Post by tcaudle » Mon May 06, 2019 8:09 pm

Likes wrote:
Thu May 02, 2019 9:41 am
I’ve shorted the terminals together, and as soon as it touches anywhere on the main frame, the light goes out.
it indicates there is a small amount of voltage on the table structure, The sensitivity is too high . We will upgrade the circuit for free for you if you go to the website and use the RMA form to send it back. Be sure to put the RMA number on the outside of the box and on the form list what is happening and that i needs a mod to lower the sensitivity. Don't use a padded envelope. it may get here is pieces....

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Re: Ohmic trouble

Post by Likes » Mon May 13, 2019 3:24 pm

tcaudle wrote:
Mon May 06, 2019 8:09 pm
Likes wrote:
Thu May 02, 2019 9:41 am
I’ve shorted the terminals together, and as soon as it touches anywhere on the main frame, the light goes out.
it indicates there is a small amount of voltage on the table structure, The sensitivity is too high . We will upgrade the circuit for free for you if you go to the website and use the RMA form to send it back. Be sure to put the RMA number on the outside of the box and on the form list what is happening and that i needs a mod to lower the sensitivity. Don't use a padded envelope. it may get here is pieces....


Any idea where the voltage could be coming from? when it was new, i had less issues but im going to say ive always had these issues, just not nearly as frequent.

also Tom, I put new switches and rewired them on my z-axis. is it still under warranty? one terminal broke off on one of the breakaway switches and there was a wire crushed in the back when i tore into it to figure out what was going on, so i just bought all new switches, rewired them with plugs, and then siliconed them for easy replacement in the future.

tcaudle
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Re: Ohmic trouble

Post by tcaudle » Tue May 14, 2019 9:53 am

Did you see the part about lowering the sensitivity to resolve the issue? Since the Ohmic Sensor card is oin the Super Z we need to either swap that card out and let you install it or get it back and rework it here. That might be a problem with the switches being glued in

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