Sticking Home/Limit Switches - Please help

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30 May 2017 07:40 #93831 by Clive S

This is a link to the exact board - but from a different supplier.
www.omc-stepperonline.com/5-axis-cnc-bre...iver-stv2-p-197.html

Yes It should have a minimum 5V but I also have 12v for the relay

If I am not mistaken this BOB requires 5V and 12-24v to the board in order for the input pins to work.

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30 May 2017 08:41 #93832 by McAdam

This is a link to the exact board - but from a different supplier.
www.omc-stepperonline.com/5-axis-cnc-bre...iver-stv2-p-197.html

Yes It should have a minimum 5V but I also have 12v for the relay

If I am not mistaken this BOB requires 5V and 12-24v to the board in order for the input pins to work.


You are correct, I read that after posting my previous comment.
Luckily I had 12v connected anyway as I thought it was only needed for the relay.

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30 May 2017 09:03 - 30 May 2017 09:04 #93833 by Clive S
You might also have to connect the two grounds together
Last edit: 30 May 2017 09:04 by Clive S. Reason: spelling

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30 May 2017 09:07 #93834 by McAdam

You might also have to connect the two grounds together


Connect the Grounds from 5V and 12V together?
The 5V supply is fed from the 12V supply which is fed from the mains, what will bridging the two Grounds accomplish? (out of curiosity)

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30 May 2017 09:53 #93835 by andypugh

Connect the Grounds from 5V and 12V together?
The 5V supply is fed from the 12V supply which is fed from the mains,


I prefer not to call the 0V reference "GND", and prefer to keep that term for the protective Earth connection.

But: Many PSUs have completely floating outputs. If the 0V of the 5V and the 0V of the 12V are not tied together then what might happen is that the +5V is pulled up to the +12V, leaving the 0V line of the 5V at 7V above the 0V of the 12V. [1]
You need to ensure that all the supply voltages share a common 0V reference.

[1] A very extreme example of this are the KBIC spindle speed controllers which have a 7V speed control voltage referenced to the +100V motor terminal

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30 May 2017 10:22 #93836 by McAdam

Connect the Grounds from 5V and 12V together?
The 5V supply is fed from the 12V supply which is fed from the mains,


I prefer not to call the 0V reference "GND", and prefer to keep that term for the protective Earth connection.

But: Many PSUs have completely floating outputs. If the 0V of the 5V and the 0V of the 12V are not tied together then what might happen is that the +5V is pulled up to the +12V, leaving the 0V line of the 5V at 7V above the 0V of the 12V. [1]
You need to ensure that all the supply voltages share a common 0V reference.

[1] A very extreme example of this are the KBIC spindle speed controllers which have a 7V speed control voltage referenced to the +100V motor terminal


Andy, I have seen you reply to many piosts on here and you sir are a legend. Thank you for taking the time to fill out that reply.
I agree about GND vs 0V but as Clive worded it GND I followed.

I will tie the two 0v together and see if that helps at all. Failing everything I@ll just make sure all switches are NO and back off them when homing.

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30 May 2017 11:31 - 30 May 2017 11:32 #93839 by Clive S

Andy, I have seen you reply to many piosts on here and you sir are a legend. Thank you for taking the time to fill out that reply.
I agree about GND vs 0V but as Clive worded it GND I followed.

I agree with Andy as well that the terminology is bad but it does depend on the background you have come from. Many pc boards have a ground plane etc. I generally refer to earth as the mains earth and gnd as the dc 0V ref point. Sorry for any confusion.
Last edit: 30 May 2017 11:32 by Clive S.

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30 May 2017 19:16 #93855 by McAdam
Well.... I connected all the 0v's (5V, 12V and 48V) and still the same issue....
More than 2 pins active and the 3rd gets stuck

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30 May 2017 21:16 - 30 May 2017 21:19 #93859 by Clive S

Well.... I connected all the 0v's (5V, 12V and 48V) and still the same issue....
More than 2 pins active and the 3rd gets stuck

I don't think I would connect the 0V from the 48V power supply if that is the one to power the steppers.

It would be a good idea to give a sketch of how exactly how you have wired this up and a pic of the switches.
Last edit: 30 May 2017 21:19 by Clive S.

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31 May 2017 11:21 #93871 by andypugh

I don't think I would connect the 0V from the 48V power supply if that is the one to power the steppers.


Indeed, it is likely to introduce noise from the chopper in the drive. Though some drives make the connection for you, unfortunately.

This is all a but puzzling.

What voltages do you see across the inputs with a multimeter?

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