Question about inductive sensor wiring in series

[Azalin]

Hello,

Looking at the attached diagram, wiring 2 PNP NC sensors in series the signal from the first sensor is connected to the power terminal of the second sensor. If I use PNP NO can I use the same method?

Another question about the resistor in the diagram. 50 OHM resistor is used for 5 volt sensors. What OHM sensor should I use for 24v sensors?

Thanks

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[dazp1976]

Hello,

Looking at the attached diagram, wiring 2 PNP NC sensors in series the signal from the first sensor is connected to the power terminal of the second sensor. If I use PNP NO can I use the same method?

Another question about the resistor in the diagram. 50 OHM resistor is used for 5 volt sensors. What OHM sensor should I use for 24v sensors?

Thanks

No. NO switches wire in parallel not series like NC.

If NO is wired in series- when 1 closes the other still keeps the circuit open so it's not good.
In parallel- if any one of them closes the circuit will see it. So now it's good.

As for the resistor. I don't think it's quite that simple. Going 24v to 5v is a big drop.
I've seen 57k mentioned and others say don't bother trying.
This is why you see 24v capable breakout boards with resistors in line with transistors, gates, diodes and open collectors etc.
This is what optocouplers were invented for. Or use dc-dc step down converters.

I just order optocoupler boards for things like this now. saves hassle, and easier/safer.
https://www.aliexpress.com/item/4000...25094c4dr6gK82
Can choose your in/out voltages, number of channels, and preferred output type pnp/npn.
The input side on these already serves both pnp or npn option.


I tried a 24v to 5v voltage divider diagram once for fun and the resistor caught fire. Was only using 1/4watt ones.
I think I needed at least 5w dissipation. (waste of power that is).


This is one of the simple diagrams I've seen for 24-5v
https://forums.ni.com/t5/image/serve...819D29A1D?v=v2
Uses 3 resistors and a transistor.

This is a basic 24-5v opto diagram:
https://aws1.discourse-cdn.com/ardui...d1b71052c4.png

[Azalin]

Hi,
Guess I was confused. The C78 board takes 24v signal (I think. Manual isn't clear. It sources the switches with 24v so it should take 24v). So no resistor is needed.

I better order some PNP NC switches.

Sent from my MI 5s Plus using Tapatalk

[dazp1976]

Hi,
Guess I was confused. The C78 board takes 24v signal (I think. Manual isn't clear. It sources the switches with 24v so it should take 24v). So no resistor is needed.

I better order some PNP NC switches.

Sent from my MI 5s Plus using Tapatalk

Yes it does. Just had a look.
RJ45_8
For pins 11,12,13,&15 inputs.
You'll need a 24v psu for it if you haven't got one already.

[tecnico_figueroa]

In your diagram, what voltage is there on the brown line?

[Azalin]

This is one of the simple diagrams I've seen for 24-5v
https://forums.ni.com/t5/image/serve...819D29A1D?v=v2
Uses 3 resistors and a transistor.

Hi,
This looks simple. Even for me : )

I'll build it for my lathe. Currently I'm using relays for 5v to the board but relays are slow.

Thanks.

[Azalin]

In your diagram, what voltage is there on the brown line?

The diagram is made for 5v.

[dazp1976]

Hi,
This looks simple. Even for me : )

I'll build it for my lathe. Currently I'm using relays for 5v to the board but relays are slow.

Thanks.

Relays are ok for switcing things on/off.
I can't be bothered trying to make circuits.
When it comes to safety circuits / fast switching items and the like, as I've said before I just get pre built high speed opto units.
Examples:
https://www.aliexpress.com/item/32914498721.html
https://www.electronics-lab.com/proj...7-optocoupler/
https://www.aliexpress.com/item/33013938014.html

[mactec54]

Hello,

Looking at the attached diagram, wiring 2 PNP NC sensors in series the signal from the first sensor is connected to the power terminal of the second sensor. If I use PNP NO can I use the same method?

Another question about the resistor in the diagram. 50 OHM resistor is used for 5 volt sensors. What OHM sensor should I use for 24v sensors?

Thanks

Why your choice of PNP

[dazp1976]

Why your choice of PNP

That's actually a good point.
I initially thought his board was connected to negative so needed connecting to switched positive pnp.
Then he mentioned the C78 which has both pos & neg going into the rj45 block.
There is no input diagram so it's unclear.

C78 pdf
https://www.cnc4pc.com/pub/media/pro...8REV1.3_V2.pdf

pnp/npn diagram
https://automation-insights.blog/201...sensor-wiring/

[Azalin]

Hi,

Mactec I just trusted the diagram and ordered the switches. I don't know why cnc4pc used PNP NC.

Anyway, I wired all the switches and they all work fine. I didn't even needed to setup Mach4 and PoKeys. But something weird is that all the switches LEDs are on by default. Going off when triggered. Is that because they are PNP NC? Is that ok?






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[Azalin]

Looks like the load is on blue in this model. So I think if I switch blue and brown then I'm good.



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[Azalin]

No, it didn't work that way.

How it works:
Brown wire +24v
Blue wire gnd

LED is on. Goes off when triggered. Have you seen an inductive switch that works this way?

[dazp1976]

No, it didn't work that way.

How it works:
Brown wire +24v
Blue wire gnd

LED is on. Goes off when triggered. Have you seen an inductive switch that works this way?

Yes.
I have some LJ12A3-4-Z/BX - NPN - Normally open type, that do exactly the same when I tested them.
Worked spot on with my controller but I won't be fitting those ones though.

I have some NPN-NC I'll be using instead which I haven't tried yet.

As long as they trigger the controller when switched.... Who cares about the specifics of their operation.

Same wiring.
Brown 24
Blue gnd
Black load