Internet PLC Forum

I have a new unit ( un programmed , as received ), out of the box that when powered up, the Tthe CPU Status LED's remain un lit. I am unable to communicate to the unit.

This is the same with Dip switch 1-4 set : Pause Red LED should be lit after power on

Please advise as to any diagnostic procedures that I might be able to do

What is the effective DC input impedance of the Analog Inputs on the T100MD-888+?.

Some of the literature indicates a 2k resistor in series with the inputs, and the forum has indicated a 0.1uf cap across the input to ground on channels 1 to 6; channels 7 and 8 donot have the cap.

What would be the effective output impedance of Channels 7 and 8 if used as Analog outputs? Do these channels have the 2k resistor in series as well?

Your assistance is appreciated

In going over what I did yesterday, I remembered that my problem started just after switching the DIP Switch SW1-1 to ON. The ladder logic, discrete I/O works, the analogs in the Custom functions work, but the High speed counters connected to the encoder do not work, also the LCD is not initialized to a hidden cursor.

This morning, I moved the DIP Switch SW1-1 back to the OFF position, and surprise, surprise,  all the code works properly, as well as the High speed counters.

So it would appear that the MX-RTC is the problem. The part is marked as a DS1216-C  which is a Dallas Semiconductor Smart Watch Ram, with a MX-RTC sticker on the side. Is this the correct component?

I've removed the MX-RTC and have left the DIP Switch SW1-1 OFF

Any suggestions would be appreciated?

I have a requirement to count the total number of pulses produced by an optical encoder connected to the T100MD-888+.

I have the A and B signals on Inputs 5 and 6 with HSC[2] and are using PMON 1 Input 3 to measure the frequency.

I have connected the A phase to both Input 3 and Input 4 thinking that I may be able to count the pulses through Input 4, measure the frequency through Input 3 ( PMON 1 ), but It does not work.

Is there a way of being able to count the total number of pulses created by the encoder? As it is now the variable will come back to zero when the encoder rotates in the reverse direct back to home base.

What I want to measure is the total round trip, i.e total pulses, both forward and reverse.

Any suggestions without having to disable the frequency measurement?

Your assistance is appreciated.

As it turns out, the Optrex DMC-16230NYj-LY-CGE-EB, being an extended temperature unit, requires a -2.5 volt level on pin #3 ( Contrast Voltage ) of the 14 pin header. We are now functioning properly.

The T100MD-888+ that we purchased, was purchased with an Industrial temperature specification of -20 Deg. C. For Low Temp operation of LCD's, it would appear that a negative contrast voltage is required. Is there any negative voltage available on the T100MD-888+?

I am having a problem in displaying anything on the LCD. I spent a lot of time setting the unit up, checking that all the pins and cabling is correct. The LCD has a 14 pin header, with pin #3 supplying the power to change the contrast of the LCD. This voltage is supposed to be adjustable by the small pot on the PLC ( Contrast Adjust ), a voltmeter on pin 3 indicates this pin is very close to ground potential, no matter the pot position, Looking at the PLC Board the pot has three pins, one connected to Pin #3 of the 14 pin header, one to pin #1 of the 14 pin header ( Ground ), the other, should be connected to +5.0 vdc, I could not see where the PCB trace went to, This pin ( on the PC Pot ) has no voltage on it when the unit is powered up. Running the demo programs show the PLC is functioning, but no info is shown on the LCD. Oscilloscope probe shows pulses on all pins but pin 5. So it would indicate that either the contrast is turned off or the new LCD is toast.

The LCD is a brand new Optrex DMC-16230NYJ-LY-CGE-EB unit purchased from Digikey

Any assistance would be appreciated