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I would need help with my application for counting impulses sent from a Hall sensor. Below is the description of the application.

In the project, I have a 2-pin Hall sensor powered by +13VDC. Depending on whether the sensor is "on" or "off", it sends voltage pulses of approximately 12V or 8V. I need to count the number of pulses in my PLC controller. I have a card that counts voltage pulses of +24VDC. I have considered using an SSR relay or an optoisolator to create pulses of +24VDC based on the voltages from the Hall sensor. The problem is that I cannot find an appropriate SSR or optoisolator that could activate at 12V and deactivate at 8V. I have considered using a voltage divider, but I couldn't configure it to work for these voltages and appropriately activate and deactivate the SSR. I have considered SSR/optoisolators for 0-5V (PXC.2964270) and 0-10V (MURR.6652500).

Below are the device specifications: Hall sensor: Power supply: 13V Resistance: 182 OHM Low-state voltage: 7.7V - 8.8V High-state voltage: 11.3V - 12.7V

PLC measurement card: 6ES7138-6AA01-0BA0

I would greatly appreciate help in finding a solution. enter image description here

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The problem is that I cannot find an appropriate SSR or optoisolator that could activate at 12V and deactivate at 8V.

You say that you can find an SSR or opto-isolation device that can run from an input of 5 volts so, why not use a Zener diode of maybe 7.5 volts, to drop the 8 to 12 volt signal to 0.5 to 4.5 volts. If using a regular opto-isolator you might need to add a series resistor as well: -

enter image description here

If you don't need an isolation barrier why not use a PLC input that is 5 volt compatible instead?

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  • \$\begingroup\$ Thank you for your answer. It looks like your solution will work. I'm just wondering if the Zener diode will operate properly with fast voltage changes. \$\endgroup\$
    – gregory_000
    Commented Mar 9 at 12:53
  • \$\begingroup\$ @gregory_000 Zeners are very fast (sub 10 nano seconds usually). If we are done here, please take note of this: What should I do when someone answers my question. If you are still confused about something then leave a comment to request further clarification. \$\endgroup\$
    – Andy aka
    Commented Mar 9 at 12:54

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