Homing & Limit Switch UNSOLVED MYSTERY! <solved>

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RJS100
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Re: Homing & Limit Switch UNSOLVED MYSTERY! <solved>

Post by RJS100 »

That is an interesting thought. The attached is how I wired them as suggested by Shawn. He noted wiring a number of machines this way. They are wired to a 24V circuit so I'm not sure if the voltage drop would be significant.

Also, section 5.7 of the install manual shows this same series wiring going to one input (Schematic S14954). I am not sure of the next steps.

Thanks for your thoughts... Richard
Attachments
5 - Pin Aviation Conector - Series Home NPN Proximity Sensor Wiring - with avaition connector.jpg
suntravel
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Re: Homing & Limit Switch UNSOLVED MYSTERY! <solved>

Post by suntravel »

S14954 is for mechanical switches, there is no problem wiring in series...

Uwe
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Re: Homing & Limit Switch UNSOLVED MYSTERY! <solved>

Post by ShawnM »

Richard, those diagrams are for "mechanical" switches not proximity switches.

There are videos on YouTube from Automation Direct and others showing how to wire proximity switches in series. There's even diagrams from Omron on how to do it and how to calculate the actual voltage drop if you want to know. It works just fine like this, it's not voodoo. :D
suntravel
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Re: Homing & Limit Switch UNSOLVED MYSTERY! <solved>

Post by suntravel »

Link from Omron:

https://www.omron-ap.com/service_suppor ... /index.asp

Keep the number of connected Sensors (N) within the range of the following equation.
iL + (N - 1) x i ≤ Upper limit of Proximity Sensor control output
VS - N x VR ≥ Operating load voltage
N : Number of Sensors that can be connected
VR: Residual output voltage of Sensor
VS: Power supply voltage
i : Current consumption of Sensor
iL: Load current
Example: A maximum of two Sensors can be used when an MY (24-VDC) Relay is used for the load.

Note:
When an AND circuit is connected, the operation of Proximity Sensor B causes power to be supplied to Proximity Sensor A, and thus erroneous pulses (approximately 1 ms) may be generated in A when the power is turned ON. For this reason, take care when the load has a high response speed because malfunction may result.

That is why I do not wire in series ...

Uwe
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Re: Homing & Limit Switch UNSOLVED MYSTERY! <solved>

Post by RJS100 »

Ok... I see the attached is for proximity sensors vs. mechanical switches. I have to think on this one. I do have two unused inputs, so I could rewire them. My instincts suggest something else is happening here. I hit the tool change button a few dozen times, sending the machine to the top of the column over and over and it stops at the exact same place. Then, just after measuring tool heights, it stops in a different position.

Thanks again... Richard
Attachments
S14955-ACORN_rev4_LIMIT-HOME_NPN_PROXIMITY_SENSORS.pdf
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suntravel
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Re: Homing & Limit Switch UNSOLVED MYSTERY! <solved>

Post by suntravel »

ToolCheck drive to Z position in G28, regardless which tool is used.

Did you check if G28 Z value have changed?

Uwe
RJS100
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Re: Homing & Limit Switch UNSOLVED MYSTERY! <solved>

Post by RJS100 »

Sorry I am new and learning g-code, Fusion 360 and machining at the same time. I am not sure I understand your question. I ran some g-code that issued a m6 T2 command followed by G1 F120 Z2 a few dozen times and watched the axis rise to the same position. Then I hit the tool change button a half dozen times and again watched the axis rise to the same position. What do you mean by check G28 Z value?

Richard
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Re: Homing & Limit Switch UNSOLVED MYSTERY! <solved>

Post by CNCMaryland »

G28 is your home position. Essentially machine position 0,0,0.

When a G28 command is issued, the machine will go the home position as determined by the last homing cycle.

What you are going issuing a G1 F120 Z2 is telling the machine to Move @ a feedrate of 120 to the position Z2. So 2" from home.

After measuring tool heights it is going to goto Z0, not Z2.
RJS100
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Re: Homing & Limit Switch UNSOLVED MYSTERY! <solved>

Post by RJS100 »

It is going to Z0 and I noted the exact same height each time. That is the relative position of the flag to the proximity sensor was exactly the same as I would have anticipated. But... for some reason, at other times I noted this not to be the case.
suntravel
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Re: Homing & Limit Switch UNSOLVED MYSTERY! <solved>

Post by suntravel »

If you only use m6 T2 the CNC will only know that it have T2 ut not the offset from T2
To tell the CNC the height offset you need to command H2 for offset 2

G1 F120 Z2 will be a different Z position with H2 or maybe H4 if both offsets are different

Uwe
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