Basics of LED Displays

mjamil · Dec 21, 2004

I need to output data to a LED display. its going to be a single line and +20 charachter display.

What I want to know is, how does the LED display work,
my understanding so far is that for each charachter of the display I would need a BYTE output? b'coz it has 7 segments?

Can someone point me in the right direction, or somewhere I can get these ready to use display.

to send this data out of my PLC (a S7226) do I need to use the outputs directly to the segments or is there a module that can be used as a translator between my PLCs babble and the displays input (RS232?)

Ken Moore · Dec 21, 2004

Try this thread:
http://www.plctalk.net/qanda/showthread.php?s=&threadid=2641&highlight=segment+display

Eric Nelson · Dec 21, 2004

What brand/model display are you using?

beerchug

-Eric

elevmike · Dec 21, 2004

The thread posted above refers to a 7 segment display. (one output for each segment). Apparently that does NOT apply to your display. You really need to provide more information on the display to get a streight answer.

Mike.

rsdoran · Dec 21, 2004

Goto Vorne for displays: http://www.vorne.com/displays.htm

THey can be canned messages that are triggered by an external input, they can standalone or be interfaced to an intelligent device.

mjamil · Dec 21, 2004

LED display

Sorry for the mess, I've always had this problem with explaining my problem

I wasn't refering to any particular brand, but since I was thinking of using one, I wanted to know How it works and whether it would be worth to include this in any future projects.

I was searching net for information, I learnt there were models which required 4-bits per CHARACHTER (each charachter divided into 7 of its typical lines/segments)

what confused me more was my requirement of so many charachters!!!!

Another issue just clicked my mind, ALPHANUMERIC charachters, these aren't 7-segments, are they?

I was thinking of a display that can be triggered directly from my FREEPORT (S7-226) or something, maybe even using a device in between to simplify the usage of ALPHANUMERIC output.

Thanks all....

jolio ST · Dec 21, 2004

E.g:
A microcontroller is programmed and a clock set to send pulse signals.
the 7 segment LED will be wired to the PIC to display the output pulses.
basically, data bits are set from 0000 to 1001, and the seven segment are set like so:
bgfaced x
7654321 0
--------------
1011111 0 - display 0
1000100 0 - display 1
1101011 0 - display 2
1101101 0 - display 3
1110100 0 - display 4
0111101 0 - display 5
0111111 0 - display 6
1001100 0 - display 7
1111111 0 - display 8
1111101 0 - display 9

More information are found in this link .
Hope it helps.

regards
Sherine T.

gbradley · Dec 21, 2004

You may also find this article on digital Clocks interesting.

Eric Nelson · Dec 22, 2004

You usually don't need to worry about individual digit control with the commercially available displays. As Ron mentioned, they're commonly triggered by discrete inputs (using canned messages), or serially, by sending them text strings.

As you've noticed, if you were to wire each (numeric) digit individually to your PLC, you would need a minimum of '# of digits' TIMES 4 outputs. That can quickly add up to a LOT of outputs. Thanks to out 'slow' eye response, this can be simplified to '# of digits PLUS 4 by multiplexing the digits. Each additional digit only requires ONE additional output. Be sure to read THIS page in jolio's link to learn about about multiplexing.

beerchug

-Eric

RMA · Dec 22, 2004

Funny how the questions crop up together.

As with the question about Thumbwheels, which I was reading about two minutes ago, many (but not all) LED displays, especially 7-segment ones, use BCD coding. So if you've got BCD commands available, which I assume (perhaps wrongly) most PLCs will have, the job becomes a no-brainer.

elevmike · Dec 22, 2004

The EZ Text panels from AD are compatable with the Siemens S7.

Link: http://www.automationdirect.com/adc..._Interfaces/EZText_Panels/EZText_Units/EZ-220

You dont want to bother with the discrete I/O thing since it'll consume your I/O.

mjamil · Dec 22, 2004

is the EZ touch compatible with the S7-200 also? as the PDF FILE mentions its compatibility with the s7-300/400

besides, the Machine panels will have a TD display, but a Huge DISPLAY IS NEEDED (prefarably with an Alarm) as most machine operator ignore what the tiny display, displays!!!! .... result....... u know....

CaseyK · Dec 22, 2004

Ron posted a link for Vorne displays. I had probably 175 of them in use in my portion of the tire plant years ago, with no failures. Easy for the hired help to program and maintain. Moderately priced.

I have used them periodically in recent years, again with no problems. I highly recommend them!

regards.....casey

mjamil · Dec 23, 2004

this would mean if a LED DISPLAY has a port to communicate properly with the PLC directly, I could try dumping ASCII?

I dont think I would have any problem to use discrete outputs from my PLC, the reason is all I have to display are certain warnings, maybe 15 or 20 of them, well?

what gets more complicate, silly of me banghead not to mention it earlier, I need an ALPHANUMERIC display, I recall this should be having 15 segments.

coments pleaseee.....

....and many thanks for the links

rsdoran · Dec 23, 2004

I will repeat
Goto Vorne for displays: http://www.vorne.com/displays.htm

The M1000 alphanumeric http://www.vorne.com/led-displays-m1000.htm
Ease of use and powerful advanced features are gracefully combined to deliver a truly innovative marquee display. Unlike many competitive products, the M1000 display field is controlled by a hardware state machine resulting in a visually superior display. Simple yet powerful ASCII commands provide complete control over display functions and are designed for quick and easy integration. Optically isolated serial ports enhance communication reliability and provide optimal electrical noise immunity even when data networks extend thousands of feet.

GY2200 http://www.vorne.com/electronic-displays-gy2200.htm
Also ASCII and serial interface.

I have used everything they have, good prices, reliable, and great support if needed.

Basics of LED Displays

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