Hi,

I am considering using Remote IO to start and stop pumps in the field.

The proposed way is to have conventional push buttons in the field next to the motor with the IO cabled to a Remote IO JB with bus connection to a Controller in the Rack Room. A Profibus connection will then start/stop the pump.

To save on IO, is there any reason why I can't just use 1 x maintained (or momentary) button in the field that can start/stop the motor rather than the conventional DOL of 2 x PBs?

I just haven't seen this before... (except in my Jacuzzi... lol)

Thanks,
Gray

 

I assume you are suggesting one button with a toggle action in the PLC. I think you might run up against a safety issue. Sometimes you see an On/Off switch with one input, that's OK because the outcome is predictable but you need to consider the safety issue of the drive starting by itself after a power bump. Better to use a separate input for Start & Stop with a Run status from the contactor to latch in.

Roy

 

From a software point of view this can easily be made to work and I have seen this done.

However, you should probably check the site standards and safety requirements of such an installation. Often a momentary signal is not considered suitable for starting/stopping a motor because there is no way of detecting a fault in the circuit. Site or national regulations may require you to have red and green buttons for example. Sometimes an indicating lamp beside the switch is a requirement. Most industrial sites would also require a local E-Stop, which isolates the power supply to the motor (independently of the control system).

Rob

www[.]lymac.co.nz

 

For testing purpose, a single PB with continuous latched output for ON & break for OFF or even ON/OFF Selector Switch can be used for motors similar to Lamp control.

But for process control of motors, definitely project specific safety & operator standards needs to be followed.

Regards,
Elavazhagan.S