24volts dc to plc

[khaja nazeeruddin ik]

hello
i am using siemens s7 300 for handling the system .we are going to add marking system which is having inbuilt plc in it ,just i have to give 24 v output from my main plc s7 300 to start trigger marking as you can see in picture (rj)
i made one output high in my main plc so i am getting 24v.
i am having 8 core cable coming from my main plc panel to terminal block in which all 7 wires are used for input and 8 wire i am using as output to take 24 volts from main plc panel to this machine.i am getting only single wire for 24 v
do i need the return path for 24v or i have to connect only 24v on the picture for plus 24 volts (rj) no need to connect on negative side
for this 24v i need to connect 24v plus side and minus side i can connect it to ground r what i dont understand
please let me know do i need to connect negative 24 to complete the path

 

[boneless]

Am I understanding correctly that you are using an output from your 1200 PLC to feed the entire secondary system?
If that is your plan, please don't.. Buy a power supply, if you are trying to save money, this is a great way to end up having to buy a new PLC. Since you have a 300 PLC, I assume you have a power supply already.

If you want to control the power going to the second system, use an interposing relay instead.

Strictly speaking, if your power supply is grounded, you would only need one wire, but I consider that bad practice.

 

[khaja nazeeruddin ik]

please let me know do i need to connect negative path for 24volts as you can see in picture (rj)
if i have to give can i connect negative path to ground as you can see in picture (rj)

 

[Kidblue]

Hi,

As stated above, check the loading you require very carefully - I'm not sure what type of O/P card you are using (relay or transistor) but there will only be a limited amount of current capacity. Having said that, if it is only triggering at signal level you should be fine.

Regarding the 24V output you are using - you will need the field system to reference the same 0V as the one from your PLC output. As mentioned, if both are earthed, then it will probably work already, but it would be better to wire a pair of cores to the remote system (1x24V out, 1 x 0V).
You could, as already suggested, use your 24V PLC output to energise a relay or contactor and then use 'dry' contacts off that to then switch the remote systems 24V supply back to itself...

Hope this helps,

Rob

 

[Highland Controls]

Based on the information you provided, you will need to provide 0VDC to the other side of the trigger input.