User/Operator Interface - PLC


Thread Starter



I need to restrict access to a remote site by having a user enter an ID via a numeric keypad which will be compared in the PLC and if true, will latch an output. This will provide how many times the user has accessed, dae/time etc. Are there any simple devices to accomplish this task? We currently use SCADAPack PLCs (modbus).



James Swanson

I've actually done it with these cheap numeric input units from automation direct. They act as a MODBUS master that write to the Control Microsystem com port as a slave. The CM unit then decides whether the code is good and triggers an electronic door lock. They also have a small display to tell the person that the code is good or bad or whatever which is read from the CM unit. All of this is tied to an HMI that keeps track of the daily codes and who enters and leaves. This is for a large municipal control room.
Hi. I was searching the web and I came across this post.

In my application, I am using a microchip DSP as my controller and I want to order a hmi to communicate with my DSP, and the automation direct product that you mentioned looks pretty good, however, they say that it is compatible with dl05... (their own plcs) and allan bradley plc, etc.

I wanted to make sure that I will be able to communicate with the automationdirect hmi with my DSP using Modbus (is that what you did?). Right now, I don't know much about Modbus communication protocol, but if I know that it is doable, I'll learn on my own.

Thanks alot!