slc 500 input card (dc source)

i have an input card producing 24 volts coming out of an input card ???
any help on this one

What model is the card? What terminal is the +24 coming out of?

You indicated in your title - it's a DC Sourcing input card.

Each internal input circuit (if you look at equivalent circuit diagrams - you didn't specify exactly which card by number) is connected between the input terminal and DC+. If you connect nothing - or an open device - to the terminal and read the voltage at the terminal with a high impedence voltmeter you will see close to the 24 volt potential - as you should. When you close the input device (which is connected between the terminal and DC common) you will see the potential drop to near zero. This is the proper operation.

This is the first input card, there"s four input cards, all four have the same program working them. 3 of the four are working properly. the input light indicator is showing on three of the input cards on the first input card the input is not showing. with the wire unhooked the input 6 is showing 24vdc on it. when you measure the voltage on input 6 on the second card with the wire unhooked it is still showing 0 voltage.

these inputs are working off proximity switches

my company sent me to look at this machine for one of our customers and im a hard wire guy a basic electrician not a plc programmer not yet anyways.

your input is very much appreaicated

to me it sounds like the input is going out in this card

I think you're confusing yourself.

The first thing you need to understand is what Allen Bradley means when they say "DC Source".

From the 24VDC power supply, the positive terminal will be connected to the "VDC" on the input card(s). The NEGATIVE, or DC COM, or 0VDC (whatever you want to call it) is what is sent to the inputs on the card when the input is made (whether it be a proximity, limit switch or whatever). Again, the NEGATIVE is what is sent to the card. This is backwards from most US made stuff, but common overseas. If you have 24 volts when you check between the VDC terminal on the card (which should have 24VDC+) and the input terminal (which should have 0VDC-) then the input should be on. If you do not have this voltage, than it isn't the card, its the physical input, wiring, etc.

If you do have this voltage between those 2 points and the input is NOT on...then yes....likely its the card.

Please post the number of the card(s) to help us in your troubleshooting. Verify that they are all the same type. If not list the part numbers for each card.

For an Allen-Bradley 'sourcing' card the input point, before any input is wired to it, should show the 24 plus voltage. Measure one of the 'good' input points with the input turned on and with it turned off. That is your reference.

yes very confused, on the other input module the input six's indicator light is on. On 3 out of the four the Input six is on. the voltage from common to the input six terminal on 3 of them is reading zero, on the one that isn't working the voltage is 24vdc. This is with the wire connect. With the wire not connect the voltage on the three that are working is zero. and the voltae on the wire is zero. on the one that isnt working the voltage on the wire is 0, and on the terminal the voltage is 24vdc.

elstrick22,

Please locate the part number located on the module.

I believe you can find it on the module door on the inside.

It should say 1746-????. The ???? is the type of card.
regards,
james

Sorry I haven't responded with the part number off this card. I was pulled off this project to work on another one and hurt my hand in the process. Main thing is the machine still isn't running. This input card is a 1746-iv16, 16 ch-dc input module for programmable controller (sourcing).

This machine and process that is being ran in the factory is a old process and they have lost all prints and schematics to this machine. I have never dealt with a sourcing input card, so my question is what brings this input in? From the information I have gathered from your feedback and the information I have researched, I understand that when this input is open that it will show 24 v dc, and when the input is on it won't, is that correct? So my question being what need to go back to the input card to bring in that input?

Thanks a lot guys.

See drawing 24vdc is what you should have at to input terminal.

Thanks that drawing will help wonderfully, the only drawing I could find wasn't the best, thank you very much.

elstrick22 said:

Thanks that drawing will help wonderfully, the only drawing I could find wasn't the best, thank you very much.

Click to expand...

You're welcome.

http://www.thelearningpit.com/lp/pdf/itv-m2.pdf

A tutorial from the perspective of a Micrologix but good reading w/ diagrams.

Use a jumper to momentarily connect the input terminal in question to DC Negative,
If the input card indicator lights, the card is good.