sensors to same port

Hello fam,

I want to connect 8 industrial inductive proximity sensors to same input port of the PLC module. The application here is, if any one of the sensor gets sensed the vacuum generator should turn ON. So, I have decided to connect all in one port of PLC to easy my program.

Open to discussion and any other ideas and suggestions

Thanks and regards,
ARCP

Hello ARCP

So if in understand correctly you want to connect 8 sensors to one digital plc input?

Can be done I think but disadvantage is When one sensor is broken you have to check in the field wich one and sometimes can be difficult. When you connect every sensor to a seperate plc input you could show their status on a scada or hmi system and would be easier for maintenance people to troubleshoot. Also if Logic has to be changed regarding these sensors it can be done more easily When they all have their own plc input.

Regards
Henny

thanks

Thanks henny


Thanks for your valuable reply. I'm short of both inputs and budget to this particular project(to add extension module). I am not using the HMI too to reduce the cost. All sensors are connected at same height and they do same work at different positions. so, I wanted to connect them at the same digital input port.

My main worry is about the current into the PLC input port incase of every sensor is getting sensed at the same time.?? Is there any way to reduce that amount of current rushing into the port at same time.??

Thanks
ARCP

Hello ARCP

You could connect the sensors to a external 24V and connect them to interface relays and bring the contact of that interface relais to the plc input. In that case you don,t have to worry about currrent. And if their is Some money left you could even use 8 interface relays and wire the contacts in parrallel to the plc input. In that case the maintenance man can check each sensor in the field and see in combination with their own interface relais.

Don,t know if that is cheaper then a extra inputmodule.

Kind regards
Henny

Do you know how to connect one prox sensor to an input?

What PLC and type of input module is being used here?

What type of signal is coming from the prox?

The original raison d'être for a PLC was to minimize the more time-consuming effort of hardware configuration in trade for the lesser effort of programming.

If that does not apply, which seems to be the case because you want to logically OR, in hardware, those prox signals together to make the programming easier, then it may be just as simple to wire the ORed result directly to the vacuum generator.

An alternative may be that there is a PLC instruction that reads several inputs into the bits of a single integer value, and checking that value can be done with as single instruction, but if you do not tell us the environment, then we cannot offer useful suggestions.

The PLC will only use the current required, i.e. if an input is rated at 10ma that is all it will draw regardless of number of sensors energised.
I assume these are PNP sensors i.e. true (24v) when sensed, I would suggest putting diodes in series with each sensor it's drop will only be 0.5v and will effectively isolate each output stage of the sensors, this is just like a multiple OR gate.

thanks for the inputs given, will look into this and implement it into my 'cost effective project'

parky said:

The PLC will only use the current required, i.e. if an input is rated at 10ma that is all it will draw regardless of number of sensors energised.
I assume these are PNP sensors i.e. true (24v) when sensed, I would suggest putting diodes in series with each sensor it's drop will only be 0.5v and will effectively isolate each output stage of the sensors, this is just like a multiple OR gate.

Click to expand...

Diodes are a good idea .
I have tried two sensors to one input using two diodes in series . .
Also, a load resistor of some kohms value, can help switch well the diodes . . .

Even if it seems you are approaching this MacGyver-style - I would still recommend a prefab product, for example, Phoenix Contacts Diode block

You can use a proximity sensor with relay output as: https://www.pepperl-fuchs.com/global/en/classid_143.htm?view=productdetails&prodid=43445

Google Search: inductive proximity sensor with relay output

If use NO contact, put then in // and if use NC contact, put then in serie.