Hardware input control

[namloc]

I am using an E10-npn+ PLC with inputs 1 & 2 connected in parallel. While on-line monitoring, input 1 is always being on regardless of the status of the hardware. I can see activity, green LED, at the input but no control of the outputs. While simulating the same program, all is OK. That is, I can toggle the inputs and get the correct outputs. I moved the hardware switch from input 1 to input 6 and changed the program accordingly, and it worked OK. I tried two new PLCs and the same thing happened with both. Could input 1 be defective on the PLC board? Please advise.

[support]

When you said the two inputs 1 and 2 are connected in parallel, do you mean that the two hardware inputs are physically shorted together and then connected to a switch? Or do you mean that they are connected in parallel on the ladder logic?

Make sure that the switch used to turn on the two inputs have sufficient current to drive the two inputs (about 10mA total). YOu can also use a voltmeter to measure the voltage present on input 1 and 2 with respect to 0V power supply when the switch is turned ON and OFF. Please let us know the measured voltage so that we have  a better idea if it is due to wiring issue, hardware issue or a programming issue.

[namloc]

The two (2) inputs, #1 & #2, are connected in parallel on the ladder logic diagram. When the switches are turned ON the voltage at the input is 0 VDC and when they are OFF it is +9.00 VDC. Note that when I am monitoring the PLC on-line, the input appears latched ON even though the input LED is not on. When performing a program simulation, the software appears OK and responds as planned.

[support]

What is your power supply voltage? It seems like your power supply voltage may be a bit low. That could be the reason why your input appear stucked ON after it is activated due to hysteresis in the circuit. The minimum power supply voltage should be at least 12V. If you raise you power supply voltage a bit it should resolve the problem.

[slabit]

Looks like your voltage at 9 volt is in the range of the logic 0 voltage of 8.5 to 24v. This will hold the input low according to the hardware spec sheet.

[namloc]

I have tried increasing the supply voltage to the PLC to +15VDC and the input at #1 still is latched ON. On-line monitoring indicates #1 input is ON regardless of the hardware input. I have changed the software eliminating input #1 and the program runs OK. Note that a program simulation of the original runs OK.

[namloc]

I noticed that when using the WinLogi v.3.5 software, that it "sees" an E+12 device rather than the E+10 device that I am using. Could it be that the PLC boards are programmed wrong?