wiring LED's with PLC

jeibarra1 · May 24, 2012

Good morning,

I am working on a program to automate a machine. I want to try my program using LEDs to represent air cylinders first for simplicity. What do I need in order to use LEDs as inputs/outputs to check my program logic? I am talking about the standard 5mm LEDs

Thank you

brucechase · May 24, 2012

Why?

If you are automating a machine and need to verify outputs, then use the LED lights on the card. You really can't use LEDs for inputs, you need a physical device to change states that will allow voltage to an input point.

Doug_Adam · May 24, 2012

You need resistors big enough not to destroy the led. Assuming your output is 24V, the resistor would be anything from 1k to about 4.7k.

bce123 · May 24, 2012

I am working on a program to automate a machine.

Is this a real life machine? could someone get hurt? The first thing to do when writing a program is to understand the process (machine) and write out a detailed description of how you want it to function. Have you written any code? what PLC will you be using? what voltages will you be dealing with?

What do I need in order to use LEDs as inputs

It sounds like you may need a better understanding of your PLC I/O. Please post a more detailed description of what you are trying to accomplish. Then I am sure you will get plenty of help.

jeibarra1 · May 24, 2012

I am sorry for the missowording. I will be using switches as inputs, and I want to wire leds on a breadboard. This machine is manually operated, and I want to install a self-loading mechanism. I just started working with PLCs this week, I am trying the best I can to understand what I read online. I know how the machine works well, its just the PLC part that Im new to. Hope this helps. I am using a AB Micrologix 1000.

Thanks

Helliana · May 24, 2012

Depends on what kind of outputs your PLC has. Micro1000s have relay, 24V transistor, and i *THINK* 120V triac. If you have AC outputs, it will take some expensive LEDs to work.

shooter · May 24, 2012

24 Volt and 10 mA is 24/0.01=2400 ohm to put in serie with the led.

Albert LaFrance · May 24, 2012

You might look at industrial LED indicators like these, which have the resistor built in so they'll run directly off 24V:

http://www.automationdirect.com/adc...22mm_Plastic/Plastic_Monoblock_Indicators/LED

A little more expensive than a "raw" LED and a resistor, but everything's in one neat package - and after the breadboarding stage, you may be able to use them in your actual control panel.

icky812 · May 24, 2012

To add to the discussion, if any of your output cards are solid state you will likely need to load the output to prevent the leakage current from turning the LED's on.

wiring LED's with PLC

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