ML 1400 failed or program corrupt dial out procedure

[bearsgone 1]

Hello Looking for the advice on how to set up dial out alarm in case if PLC failed or program got corrupt. The deal out modem has two digital inputs but they wont be useful if PLC fails. Is there a third party device that might accomplish the task of detecting the failure? Thank you

[Steve G 1]

Why don't you take a PLC output and switch a relay, then wire the modem input through a normally closed contact. Program the output to stay on while the PLC is running. If the PLC fails then the output will trurn off and the relay will close the contact and send the input to the modem to dial out.

[bearsgone 1]

Thank you for the suggestion but do not think it will work. Modem input has to be energized in order to send out an alarm. If PLC out is ON, it will go OFF when PLC fails. Nothing will be dialed out since it calls on energize not on deenergize. Unless I missing something?

[OkiePC 14]

If you wire the input to the modem through a normally closed contact, and have the PLC hold the relay energized, then the modem input will only turn on when the PLC is not running.

[bearsgone 1]

Re: OkiePC. I will try that. What if I have to modify a program remotely, in this case I will have a false alarm going out without somebody manually unplugging a modem. Thank you

[Steve G 1]

the 1400 model lets you online edit the program so unless you are remotely uploading a program or turn it from run to program the output should not go out. I have done this on another project and it worked well. If I had to do something that required me to change the state of the PLC from Run to Remote I just called the client and let them know. If you are doing remote access and or changes to the program while not on site it is always a good idea to let people know you are online with the PLC, so they can monitor any problems which could occur while remote access is happening.