Need guidance on E-stop/Disconnect Switch connections

tommylight
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14 Nov 2022 11:24 #256678 by tommylight

Replied by tommylight on topic Need guidance on E-stop/Disconnect Switch connections

Yes, that looks OK.

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Sray69
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14 Nov 2022 16:38 #256700 by Sray69

Replied by Sray69 on topic Need guidance on E-stop/Disconnect Switch connections

WOW! That is surprising. Maybe I am starting to understand.

Thanks for your assistance.

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snowgoer540
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15 Nov 2022 23:16 #256811 by snowgoer540

Replied by snowgoer540 on topic Need guidance on E-stop/Disconnect Switch connections

Sray69 wrote:
tommylight,
Let me know what you think of this drawing. I came up with this iteration from another diagram I drew up that included a relay. I just removed the relay and rewired the E-stop.

I have 24V field power going through the NC side to a digital input. I am thinking this could work if I invert the state in HAL to "NOT". Does that sound right?
Also I fed the drivers using the 5V/GND from the unused stepgen on the Mesa. I ran the 5V through the NO side of the E-stop.

I would appreciate any help correcting my drawing.

drive.google.com/file/d/1n7JjQKnKvbeVyd4...j1N/view?usp=sharing

This does not look OK to me. If you lose power momentarily, there may be nothing stopping your machine from continuing on its way when power is restored. If a driver goes on the fritz, there's nothing killing the power to it.

Anyways, I don't know your application (commercial shop or hobby home based), but here's a schematic from Tormach: forum.linuxcnc.org/24-hal-components/439...stop?start=10#223294 C1 is a contactor. The one I used has 3 AC legs, and one DC leg. They are all NO I used the DC one to break the 24v circuit to the MESA card input.

I honestly dont know if they follow the ISO estop standards I've seen on other threads. But I will say that there are a ton of Tormach machines out there using this. Some in a small business setting, some hobbyist, and probably even a few commercial. Consider if that's good enough for your application.

Hope it helps.

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tommylight
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15 Nov 2022 23:32 #256812 by tommylight

Replied by tommylight on topic Need guidance on E-stop/Disconnect Switch connections

Snowwy, the DM860 he is using are stepper drives, no matter what happens to them the motors will not move, they can literally be on fire and motors will not move, just slowly burn.
Same goes for 3 phase DC servo systems, they do not move on drive failure. These can have software issues that can send the motors flying.
The only "unsafe" ones are brushed DC servo systems, on drive failure when outputs short, the motors will fly at full speed. On most of these, encoder issues will also send the motors flying.
New servo drives, better ones that is, have protections against loos of feedback.
Am i repeating this enough?

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snowgoer540
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15 Nov 2022 23:51 #256815 by snowgoer540

Replied by snowgoer540 on topic Need guidance on E-stop/Disconnect Switch connections

Perhaps, I'm just trying to say that electronics sometimes fail in wild and spectacular and unpredictable ways. Power surges do nifty things to them as well. A contactor is pretty cheap insurance to prevent mechanical equipment from being re-energized when you didn't intend for it to be de-energized under very unideal circumstances.

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Sray69
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16 Nov 2022 03:31 #256827 by Sray69

Replied by Sray69 on topic Need guidance on E-stop/Disconnect Switch connections

Thanks for the input Snowgoer. Tommy pointed out how the drivers are designed to keep the motors from running amuck if power is disrupted momentarily, which by the way is new to me as well. But I also plan to use a magnetic latching master on/off switch to my cabinet. It is my understanding that if power is disrupted the switch will stay off even if power comes back on, at least until I manually reset the switch. If this is correct, then all power to the CNC will stay OFF if power is disrupted.

Please correct me if I am wrong.

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andypugh
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17 Nov 2022 23:14 #256980 by andypugh

Replied by andypugh on topic Need guidance on E-stop/Disconnect Switch connections

Part of what Tommylight is saying is that it is quite hard to make a stepper motor turn, the driver has to switch the poles in complicated ways.
It's really unlikely for a failure mode to achieve motion.

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tommylight
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17 Nov 2022 23:58 #256991 by tommylight

Replied by tommylight on topic Need guidance on E-stop/Disconnect Switch connections

Sorry for failing to find a better way to explain that, but sometimes it takes a kick in the b#tt from someone, thank you Andy, to realize that.

As soon as i read Andy's reply, it dawned on me that i could do it better, i hope:
--Take a battery, 1.5V or 3.7V or 12V and
-wire it to any stepper motor wires = it will not spin, made to work with pulses
-wire it to 3 phase motors = do not spin, made to work with pulses
-wire it to Brushed DC = they spin as they are made to work like this.
-- No matter how much DC voltage you push through the first two, they do not spin, they will burn, but not spin.
-- All drives, be it AC or DC powered ones will convert to DC and the output stages on all types of drives work under DC power, so when they fail the output will be DC power
-- From the above it is easy (yeaaah riteee

) to conclude that the first two types have no way of moving when output transistors fail, so require less safety features.
Is this a better explanation?
Feel free to critique when i mess up explanations, i would really appreciate that.
Thank you.

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Sray69
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18 Nov 2022 00:52 #256996 by Sray69

Replied by Sray69 on topic Need guidance on E-stop/Disconnect Switch connections

tommylight wrote:
Sorry for failing to find a better way to explain that, but sometimes it takes a kick in the b#tt from someone, thank you Andy, to realize that.
As soon as i read Andy's reply, it dawned on me that i could do it better, i hope:
--Take a battery, 1.5V or 3.7V or 12V and
-wire it to any stepper motor wires = it will not spin, made to work with pulses
-wire it to 3 phase motors = do not spin, made to work with pulses
-wire it to Brushed DC = they spin as they are made to work like this.
-- No matter how much DC voltage you push through the first two, they do not spin, they will burn, but not spin.
-- All drives, be it AC or DC powered ones will convert to DC and the output stages on all types of drives work under DC power, so when they fail the output will be DC power
-- From the above it is easy (yeaaah riteee ) to conclude that the first two types have no way of moving when output transistors fail, so require less safety features.
Is this a better explanation?
Feel free to critique when i mess up explanations, i would really appreciate that.
Thank you.

I can tell you from someone who know very little about this, that makes perfect sense. Thanks for the detailed explanation.

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