Wiring problem

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22 Jul 2018 12:37 #114666 by BigDo
Wiring problem was created by BigDo
Hi,

i have a ZP5A-int BoB and my question is:
is it possible to wire a 10V-24V PNP inductive sensor(BALLUFF BES00CK) to this BoB?

thanks and regards

Niko
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22 Jul 2018 23:52 - 22 Jul 2018 23:55 #114681 by curtisa
Replied by curtisa on topic Wiring problem
Have you tried emailing the manufacturer of the breakout board?

On a casual look at the data I'd say yes, it is possible, although not without some caveats.

The minimum supply voltage requirement of the inductive sensor is 10V, so a separate power supply is required.

The sensor is configured as PNP normally-open, so on approach to the limit position the sensor output will pull up to a positive voltage. The inputs on that BoB appear to be expecting to pull down to 0V from 5V, so you'll likely find that the limit switch inputs will be permanently in the active state in LinuxCNC and unable to change over. The output of the sensor will need inverting and converting down to the 5V limitation of the BoB inputs before being applied to the inputs, either with an additional relay between each sensor and the BoB, or with some additional circuitry such as a transistor switch or inverter chip (say a CD4049).

The neater solution would be to use an inductive sensor with an NPN normally open output (ideally capable of being run at 5V if getting a separate power supply is problematic), or probably better for this particular BoB, normally closed mechanical microswitches.
Last edit: 22 Jul 2018 23:55 by curtisa.
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24 Jul 2018 09:14 - 24 Jul 2018 09:31 #114734 by BigDo
Replied by BigDo on topic Wiring problem
Thanks for the answer. Can you take a look at my schematic? Is it the right way?

Regards

Niko
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Last edit: 24 Jul 2018 09:31 by BigDo.

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24 Jul 2018 10:10 #114735 by curtisa
Replied by curtisa on topic Wiring problem
The version on the right would be the way to do it (and the way I have done it). I'm pretty sure you can leave out R1 and the connection to the 5V supply on the collector of the transistor for this style of BoB.

You can even add multiple PNP sensors in parallel to the input of each transistor switch. This allows you to have two sensors for each axis limit connected into the same input on the BoB (say positive and negative X-axis limit switches). Any sensor will trigger the BoB limit switch input.

C1 is optional if you experience noise issues with false triggering of the sensors. You may get away without needing it, but it wouldn't hurt to leave space for it if necessary.

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24 Jul 2018 16:47 #114753 by BigDo
Replied by BigDo on topic Wiring problem
without C1 i have little spikes over 5V i don't know if that is a problem.
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24 Jul 2018 22:28 #114771 by curtisa
Replied by curtisa on topic Wiring problem
For such a small spike it shouldn't be an issue in practice. Simulated circuits are great for giving you an idea of how a circuit will behave, but rarely present the true picture in real life.

I didn't need C1 when I built a very similar looking circuit for my PNP sensors.

Build the circuit first and see if it works as expected. If you start getting problems triggering because of that little spike, then C1 can be added. I'd personally position it between the collector and ground, as the spike is being generated at the output of the transistor rather than the input. If you do need to add C1 make it as small a value as you can get away with. It may only need a few hundred pF.
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16 Mar 2019 15:13 #128743 by BigDo
Replied by BigDo on topic Wiring problem
I tried to wire my new lathe but something is wrong. I can not get my home sensors up and running.
Has someone an idea why this does not work? The sensor triggers but the state on the BoB does not change.

Regards

Niko
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16 Mar 2019 16:17 #128747 by tommylight
Replied by tommylight on topic Wiring problem
If i remember correctly that BOB does not have pullup resistors on the inputs, so check that with a DVM or a small LED between the GND and one of the input pins, it should show near 5V or light the LED.

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16 Mar 2019 17:09 - 16 Mar 2019 18:13 #128756 by BigDo
Replied by BigDo on topic Wiring problem
yes between the GND and the input pins i measured 5 V.
what value must the resistor have between collector and input pin?
Last edit: 16 Mar 2019 18:13 by BigDo.

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16 Mar 2019 23:27 #128783 by tommylight
Replied by tommylight on topic Wiring problem
No resistor there, that should work as you have it in the drawing.
Are you sure you are using an NPN transistor? Did you check that same input when the switch is on? It should show very little voltage.
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