PLC display

I need to display a counter value onto a display so that the machine operator knows when he has set the machine to the correct height. The problem is that I only have 2 spare digital outputs to do this with, no option to get further cards or HMI. The plc's are fxo and siemens s5 115, and the display i have beeen looking at are Hengstler Tico 731. The display has a data and a clock input, but i don't have any idea how to transmit the data through 1 output, can anyone give me any pointers in either plc code.

Thanks in advance
Alex Kay

Your best bet is to use an operator interface and a serial communications connection to the PLC in question. If you use the same brand of O/I on both, making sure it has communications drivers for each brand, you only need to create one configuration and just change the data addresses for the two different systems. EXOR and AutomationDirect.com ERZTouch both support Siemens and Mitsubishi.

Just to add emphasis to what Tom was saying. It seems you have NOT acquired anything to "display" this information ...yet!

Its possible that an HMI would be as cost effective as another device that just displays alphanumeric.

For options look at using an HMI with compatible communications, it may offer even more options for the operator, alarms, security factors etc and be in a comparable price range.

Given the limitations you've imposed on yourself, the best I can suggest is to connect the digital output to a lamp. Set up ladder logic to blink the lamp for a number of times corresponding to the most significant digit, wait, then blink the number of times corresponding the the next most significant digit, and so on until you've covered all digits. Then wait for a longer time and repeat the process.

You would display the value 123 as:

BLINK.....BLINK..BLINK.....BLINK..BLINK..BLINK...............BLINK.....BLINK..BLINK.....BLINK..BLINK..BLINK

As you described, the display need 2 digital outputs from the PLC: a data-signal and a clock-signal.

Because the data is serial, you have to clock/latch the data.

Lets say your display have 4 digits with the possibillity of decimal point. Each digit can be given with 4 bit (or 1 nibble) + 4 bit for the decimalpoint-position. In total 5 * 4 bit = 20 bit.

Since the clock output needs to go off and on to latch the each bit, you need 2 PLC scan for each databit.

So after 40 PLC scan you have transfered all data to the display.

This was only an example. You have to read the manual regarding your display to see if it is similar.

To continue my example:
If you want to display 1234 without decimal point, and the decimal point is the first nibble in the serial data, the datasequence may look like this:

         bit+0                       bit+19 

                     1    2    3    4

DataOutput:   0000 0001 0010 0011 0100

Remember that clock have to go off and on for each databit!

I dont know that Hengstler HMI, but..

Even with DATA and CLOCK you have a LOT of programming to do.

kalle has described how you define the "bitpattern" for some data.
But that is not enough.
You have to tell the HMI when a new value (consisting of several nibbles, bytes, or words) starts.
And you have to tell when a new nibble (or byte or word) starts.

In short, you are remaking the syncronized serial protocol with 2 PLC outputs.
Think about frame, number of bits, stop bits, parity.

If the bitpattern in kalle's example was offset with only one bit, it would generate a completely wrong value.

Do yourself a favor and get a HMI that can talk to both PLCs natively. You can then add even more functionality to both PLCs with ease.

Ahaaaa..

That Hengstler is a counter !

OK, I guess you can set it up to simply count one input ("data" ?), and reset it with the other input ("clock" inverted ?).
You have to check up on the exact setup yourself.

I would simply program a generic clock-generator in the PLC (as fast as possible, but so that the outputs are certain to make the ON-OFF-ON-OFF transitions.
You have to investigate the latency of the output youself (possibly through experimenting), but I would guess it lies within 5-30 ms.
Then, when a new position has to be displayed, I would remove the reset, and start counting up until the set value is reached.
I dont know if the Hengstler can display a decimal value. You may have to stick the decimal point onto the display permanently !

edit: The problem with this approach is that it will take a looong time to display a large value.
Example "1234.5":
12345 x 2 x 5 ms = 123.45 seconds !

I didn't bother to check this display either....

but I am sure such beast's exist, e.g. 4 digits display with only clock and data input.



Here is an example, but it have 3 inputs: ENABLE, DATA and CLOCK, and 6 characters/digits LED display.
http://www.sbc-support.ch/pcd7/dxxx/d1xx/pcd7d120.htm

The documentation is PLC brand specific, but I know other brands have used this display.

If you have only 2 output, and need enable to synchronize (I am not sure, but I believe that), one solution is to use an external timer connected to clock output, and have a break between each number.... (and with number, I don't mean digit)
If you can ignore the on- or off delay of the timer-output...

I'm not familiar with the display Kalle mentions in post #8 but, this might work if the enable for that display only needs to be at a level to be active:

Tie the enable input of the display to whichever level 'enables' it, then drive the data and clock inputs from your ladder program. I've never used the PLC's mentioned but a general form would be to shift either the MSB or LSB to the output then pulse the clock output to store that bit to the display. To insure correct data, I would send a string of (16?) zeroes before each transmission of height data in order to clear out the old stuff and start fresh.

The operator might have to endure a period of display instability while the new data is being shifted in.

Thanks for your reply's. I thought that this route was going to ba a tricky one. My new solution is to use 1 of may spare outputs to drive some relays that are connected to some of the other outputs, as these outputs are not needed while the machine is changeing height i can send the height information in BCD format straight to a BCD input 7 seg. display, this is also cheaper than the hengstler unit so the boss is very happy! The only problem is that the display cannot be on while the conveyor system is running, unless I find a 7seg. display that holds its last value.


Alex K.

this is also cheaper than the hengstler unit so the boss is very happy!

Click to expand...

Do you work for free? How much time have you already invested in this? How much time are you going to spend making it work? Are you sure that the best use of your time and talents is dreaming up clever work-arounds for self-imposed constraints? Are you spending a dollar to save a dime?

Please don't take this as criticism, but these are questions you should be asking.

I agree with Steve, trying to do what you want with only a few outputs seems to get more complicated for each post in this thread.
you should rephrase the question to:
"Which display solution is the cheapest for displaying info from a Siemens S5-115U and a Mitsubishi FXO"

An OP7/PP from Siemens is approx 500 €/$
I dont know about the Mitsubishi.

Some 3rd party displays can connect to both S5 and Mitsubishi, and some can connect to several different PLCs at the same time.

Last idea: On ebay.de I sometime see OP7/PP at really low prices !