How to display 4 digit bcd data using a single digital output of PLC

[archana_sharan 0]

I have to display certain shop data on 4 digital display meters. If I used BDC meters and use the conventional output method i.e. 4 Digital outputs per digit, I will require a huge number of outputs. Is a there a way by which using a single digital output per meter, I may send the data to the meter.

[finfin 0]

I think there are some kinds of multiplexed data BCD displays that use 4 lines for data then one line for each 7-segment display (each digit) that you want to address. It may be easier to find a small HMI that you can talk ethernet and send data that way. Edited 20 Mar 2007 by finfin

[OZEE 5]

How are you planning on controlling each of the seven segments of each number with a single digital signal?? Using BCD will require a minimum of 4 bits to generate 0-9.

[gravitar 3]

well from what i recall from electronics class years ago, there's TTL decoder chips that can take discrete signals and correlate that to the appropriate 7-segment numeral display. so it's certainly possible. breaking down the serial "packet" into multiple digits would take a little more circuitry. the question is, what are these particular displays he's got set up to handle? and would it make sense for him to make a small circuit to interface the PLC's output line to the display?

[asterof 0]

Yes, use a red lions BCD input display It is programmable to display messages based on digital value inputs this means that you can have 15 messages for four digital inputs based on how you set the outputs. You use a serial cable and free software, connect to the red lyons meter and enter the message and the trigger value Program the fifteen messages, then when that value pattern goes true that message is displayed. If the message display your using works the same way, no problem.

[gravitar 3]

I hadn't considered that he wants to display canned ASCII messages, I figured he wanted to display integers. We'll have to find that out!

[TConnolly 13]

An optimate http://www.optimate.com/products/optimate/index.html or redlion http://www.redlion.net/Products/HumanMachi...geDisplays.html display unit will cost you less money and be less work and less hassle and all around make your life easier. Edited 20 Mar 2007 by Alaric

[archana_sharan 0]

I have to display integer data only. Is there a method to program a PLC Do channel to output an integer data through a train of pulses like in serial communication. That will greatly reduce my I/O count. I dont want to make the meter a separate node on the network as the network already has several PLC and Remote I/O nodes at various places.

[Ken Moore 23]

Perhaps converting the integer to ASCII and sending to an ASCII display would be better. You would not need any I/O, just a serial connection from the PLC to the display, this assumes you have ASCII output capibility in the PLC and an available serial port. There are RS-232 to RS-485 multiplexers that can send the message to many different stations, while only using one serial output from the PLC. I done this with a SLC 5/04 before to display current production counts at many different spots along the production line. By using RS-485, I believe the maximum distance is around 4000 feet.