Using npn Inductive sensor for end stop.
- Rune_cnc
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29 Apr 2025 12:10 #327287
by Rune_cnc
Using npn Inductive sensor for end stop. was created by Rune_cnc
Hi can someone tell me if mine are broken.
i cant understand these. They are stock part on the cnc machine.
And would like to keep it stock.
here is one of the switches. Attached.
I use an new 7i76U board. And can easy just trigger the end stop pin with a wire from positive source (+)
Since this gives reverse. I did think to add a relay.
but the relay just stays on.
How do these work. I get constant 24 volt.
but when messure resistanse it does from 4ohm to 40ohm.
so something is happening. When it switches and led goes on/off too.
Anyone know these.
https://photos.app.goo.gl/jcqMZvWbBJQ8ZE1p6https://photos.app.goo.gl/jcqMZvWbBJQ8ZE1p6
i cant understand these. They are stock part on the cnc machine.
And would like to keep it stock.
here is one of the switches. Attached.
I use an new 7i76U board. And can easy just trigger the end stop pin with a wire from positive source (+)
Since this gives reverse. I did think to add a relay.
but the relay just stays on.
How do these work. I get constant 24 volt.
but when messure resistanse it does from 4ohm to 40ohm.
so something is happening. When it switches and led goes on/off too.
Anyone know these.
https://photos.app.goo.gl/jcqMZvWbBJQ8ZE1p6https://photos.app.goo.gl/jcqMZvWbBJQ8ZE1p6
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- langdons
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29 Apr 2025 15:19 #327298
by langdons
Replied by langdons on topic Using npn Inductive sensor for end stop.
Huh?
Please clarify.
What exactly do you intend to achieve?
Please clarify.
What exactly do you intend to achieve?
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- PCW
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29 Apr 2025 17:33 #327305
by PCW
Replied by PCW on topic Using npn Inductive sensor for end stop.
To use NPN sensors with 7I76U inputs (which need a positive signal to actuate),
you must add a pullup resistor to each 7I76U input connected to a NPN switch.
+24V --> resistor_pin_1 --> resistor_pin_2 --> NPN output + 7I76U input
Suggested resistor value is 2.2K 1/2W
(PNP sensors need no additional components)
you must add a pullup resistor to each 7I76U input connected to a NPN switch.
+24V --> resistor_pin_1 --> resistor_pin_2 --> NPN output + 7I76U input
Suggested resistor value is 2.2K 1/2W
(PNP sensors need no additional components)
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- Rune_cnc
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05 May 2025 10:22 #327749
by Rune_cnc
Replied by Rune_cnc on topic Using npn Inductive sensor for end stop.
I think this is where my confusion comes in.
Because i only have one pin to use.
The home input.
I hooked up an external power supply.
And a switch from the positive lead.
Would this be the correct ting to do. Attachement 1.
Or do I need to add an extra resistor prior to the pin in or prior to npn signal.
Feeling like swimming with no land in site.
So im must be going about this the wrong way.
My brain hurts trying to think about this.
Im honestly trying.
Maybe best to get some other switches.
Because i only have one pin to use.
The home input.
I hooked up an external power supply.
And a switch from the positive lead.
Would this be the correct ting to do. Attachement 1.
Or do I need to add an extra resistor prior to the pin in or prior to npn signal.
Feeling like swimming with no land in site.
So im must be going about this the wrong way.
My brain hurts trying to think about this.
Im honestly trying.
Maybe best to get some other switches.
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- hermann1976
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05 May 2025 20:47 - 05 May 2025 20:48 #327784
by hermann1976
Replied by hermann1976 on topic Using npn Inductive sensor for end stop.
Hi, i also use NPN Sensors for homing and limit switches by my 7i96s without any resistors.
I thing it is also by the 7i76u not nessesary to use a resitor. The i/o's should work from 5 to 28V. Description Screenshot from mesa below.
It is not very difficult to bind the sensors: L1 (brown) to DC 24V current power , L- Blue on ground. The switch cable ist Black (BK) an is to connect to the input pin of 7i76u.
But, please without guarantee.
I thing it is also by the 7i76u not nessesary to use a resitor. The i/o's should work from 5 to 28V. Description Screenshot from mesa below.
It is not very difficult to bind the sensors: L1 (brown) to DC 24V current power , L- Blue on ground. The switch cable ist Black (BK) an is to connect to the input pin of 7i76u.
But, please without guarantee.
Last edit: 05 May 2025 20:48 by hermann1976.
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05 May 2025 21:20 #327791
by PCW
Replied by PCW on topic Using npn Inductive sensor for end stop.
Rune_cnc:
Yes, your picture with the NPN sensor and 2.2K pullup to +24V is correct.
hermann1976:
The 7I96/7I96S can work without resistors with PNP or NPN sensors.
This is because they have a floating common pin for their inputs so can
sense either a connection to positive (PNP) or negative (NPN) voltage
relative to this floating common pin.
The 7I76/7I76U does not have a floating input common pin so can only
sense positive voltages. Since NPN sensors do not output a positive
voltage, but just a sense dependent connection to ground, an external
resistor must be added to pull the NPN sensor output to a positive level.
Yes, your picture with the NPN sensor and 2.2K pullup to +24V is correct.
hermann1976:
The 7I96/7I96S can work without resistors with PNP or NPN sensors.
This is because they have a floating common pin for their inputs so can
sense either a connection to positive (PNP) or negative (NPN) voltage
relative to this floating common pin.
The 7I76/7I76U does not have a floating input common pin so can only
sense positive voltages. Since NPN sensors do not output a positive
voltage, but just a sense dependent connection to ground, an external
resistor must be added to pull the NPN sensor output to a positive level.
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- Rune_cnc
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07 May 2025 13:28 #327946
by Rune_cnc
Replied by Rune_cnc on topic Using npn Inductive sensor for end stop.
Thanks I got 1 of 3 to work.
So now I know i need new ones.
So I will just order som pnp
And do without extra components.
Make it easy on the "next guy" comming to repair.
So now I know i need new ones.
So I will just order som pnp
And do without extra components.
Make it easy on the "next guy" comming to repair.
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