Internet PLC Forum

Contrary to your statement, the T100MD888+ PLC is fully capable of receiving binary data using the INCOMM command. It will return whatever binary data it receive one character at a time until buffer is empty and then it will return -1.

Do you have an LCD display? If not, how are you going to show the characters received by the PLC? You can't use the same COMM port for receiving character from the 68HC12 and use it for on-line monitoring because the TRiLOGI software online monitoring sends commands continuously to the PLC and will fill up the buffer quickly.

For what you tried to do (i.e. to have the PLC received the ASCII character for "5" followed by a CR), you can use a clock pulse to periodically check the serial port input and find out if you receive the string "5". If so, turn on an output:
   Clk:1.0s                     Fn_#1
|--||----------{dCusf}

within Fn_#1:

A$ = INPUT$(1)
IF LEN(A$)<> 0
   IF VAL(A$)=5  
        SETIO  OUT1
   ENDIF
ENDIF

If the PLC receive the string "5" it will convert it into integer if it finds that the value received is indeed equals 5 it will turn on the output with label name "OUT1". (You need to define an output with the label name "OUT1" for the program to compile properly.)

There are also many factors to consider for a successful communication. The baud rate and communication format settings must be the same for both the PLC and your 68HC12 board.  You have to make sure that everything are set up properly before trying to verify the communication result.

Did you connect the small signal booster board in between the expansion cable and the HMI? The signal booster board is to provide a boost to the expansion signal to take care of the impedance of the the long HMI cable that is plugged into the expansion port.  The signal booster board and the installation diagram is provided with the HMI packaging. Furture version of T100MD+ will include the booster signal on board so that the booster board is unncessary. If the booster board doesn't solve this problem then you can contact us at 877-874-7527 to arrange for a replacement

The LCD backlight is designed to be ON all the time. If you connect the right voltage and biasing resistor it is alright to leave it on all the time.  (You must connect the 150 ohm resistor in series to the 24V power supply).

When the PLC output is off, the output terminal is pulled up to 24V via a 10K resistor. If you connect the output to the LED then the LED is presented with a reverse voltage of 24-12 = 12V. Although this will not turn on the LED, but most LED are specified with a maximum allowable reverse voltage of about 5V. While I don't think a weak pull up voltage will cause any damage to the LED we won't know the long term effect.

So if you want to connect the LED to 12V power supply, you should connect a rectifier diode in series with the LED. The rectifier diode can tolerate much higher reverse voltage and will protect the LED from the 12V reverse bias when the output is turned OFF. When the output turns on, the current can flow from the 12V power supply through the LED and the rectifier into the 0V of the PLC power supply. Note that the LED 12V power and the PLC's 24V power must have common 0V.

                                LED          1N4001
+12V ----|>|--------|>|----------- PLC output.



The diode method can also be used when you intend to connect to a load with a lower power supply voltage than the PLC.

The T28H-Relay does not support MODBUS so you can't use it with the Wonderware driver. There is not much we can do about it except to ask you to switch to a T100MD+ PLC.

For M-series PLC such as T100MD+ or T100MX+ you can change the PLC baud rate to other values such as 300,600, 1200,2400,4800,9600,19200, 38400. You can even change the communication format to 7 or 8 data bits, 1 or 2 stop bits and odd, even or no parity. It is very flexible. The PLC can also be used as MODBUS master as it can send out MODBUS ASCII or RTU message to other MODBUS slave.

We don't offer specific interface for a particular class of temperature transducer. What the M-series PLCs have are generic ADC that accept signals that range from 0 to 5V (on T100MD1616+ there are 2 channels of 0-1V ADC).

If your temperature transducer/transmitter can be configured to produce 0-5V output then you can connect them to the T100MD888+'s analog input directly. Otherwise you need to get signal conditioner to convert the sensor's output into 0-5V.

What Allen has mentioned is a type of servo controller that combines the advantage of stepper motor and servo motor. Unlike a stepper motor which is an open loop system, this type of servo is a closed loop system with encoder feedback but the loop is closed at the driver and not at the controller.

An ordinary stepper driver translates the pulses it receives into rotating electrical phase current to turn the motor. But the stepper driver does not know if the stepper motor ACTUALLY MOVE the required number of steps.  Slippage can occur which means that there is always a possibility that the stepper motor is off position but the controller does not know about it.

For an intelligent servo, the servo accepts the pulses and directional signal from a stepper controller (such as the PLC's stepper output) but make sure that the motor DO turn the number of steps that it receive by check on the position feedback from an encoder.

Regarding your LCD display with funny characters, we would like to check with you for your configuration. Please email us your contact number to support@tri-plc.com so that we can call you for more detail info about your setup.