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Questions about making a PLC "training" box

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I am planning on making a “trainer” box out of a ML1100 that I have for trying out some simple code without breaking into a production machine. I’d like to add a potentiometer on the front to simulate a pressure or flow signal. Just wondering what is the best way to do this? - A 4-20 ma signal. What would I need to supply this and can it run through a potentiometer? - Is a 0-10V signal easier? I have a 24VDC power supply in the enclosure already. Can I tap into that and run it through a pot? How do I cap it at 10V so I don’t go to high? - Any suggestions on a pot that will give me a lot of resolution? - Is there an inexpensive, small display I could add to show me the actual current or voltage so it’s not just a guess? Thanks.

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This is how you can build a basic current source fairly easy, although its not the most accurate way, it should work just fine. It will give you 3.69ma to 20ma. Also, add somthing like this or you could strip down a cheap multimeter, if you wanted to go digital. Those would be your cheapest options. Edited by Richard_Nixon

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The '1100' doesn't have current inputs, just a 0-10 V input. For a 4-20 ma circuit to work with it you would place a precision 500 ohm resistor across the input. This will give 2-10 VDC for and input of 4-20 ma. But then to use the the circuit shown by Richard_Nixon you would have to subtract 500 ohms from the fixed resistor to make a current source compatible with the input circuit. And just provide monitoring jacks to plug in a multimeter. Provide for opening the circuit for a current measurement. PLC programmers absolutely should have a grasp of basic electrical principles at least before starting. To program a real-world machine they need the basics in all things used in the machine: mechanical (basic Physics at least - how things start and stop, how they move, how they rotate), pneumatic, hydraulics, electrical as mentioned above. I, for one, built hobby computers (late '70s). This provided an excellent start to the concepts of the computer arithmetic, number storage, program structure, speed of operations. I doubt that many starting in PLCs today can ever have the same type of experience. Edited by b_carlton

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Use a 10-turn pot. Edited by ScottC

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