getting my click plc to communicate with a rs232 commercial scale

jcollins · Mar 1, 2020

I'm trying to get my click to receive data sent from my commercial scale for a farming application. I'm having a hard time getting the 2 to interface. I'm not sure I'm following the connections right. attached are the 2 pages of the scale manual for the rs232 connection of the scale. I did notice when I tried to set up the receive command in the click that the one of the rj12 wires needs a 5v connection. this scale had some print near the port saying it was 7-10v. I'm not sure if that's contributing to my confusion. any perspective on this is appreciated.
If there is a better/easier commercial scale to work with I'd love to know about it, I need to be able to measure in grams though.
scale model is a EW-1500i from A&D
http://drive.google.com/open?id=17GxtH0jw6eTUj-5a5P7SlbaRxJ7bKsnC

http://drive.google.com/open?id=1UP9XTnTZfKYvWOQKfkpwGg9QjzfnAOw2

KirkC · Mar 1, 2020

Try this.

CLICK SCALE
0V <-> pin 5 (signal ground)
RX <-> pin 2 (transmit)
TX <-> pin 3 (receive)

pin 7 & 8 jumpered on scale

jcollins · Mar 1, 2020

Sorry kirk not the fix. I'm getting a bunch of $00 in the monitor view

OkiePC · Mar 1, 2020

Are you trying to send and receive ASCII on the same port?
If so read here:
https://forum.automationdirect.com/...-plc/127245-looking-for-example-ascii-recieve

And post your click program if you're allowed (zip it first).

jcollins · Mar 1, 2020

Honestly there is no program so far, I'm constructing a packing machine for salad and the first problem Which will tell me how viable it'll be the is the "auto weighing" mechanism. So step one is getting a legal for trade scale to interface with my plc and build around that.

jcollins · Mar 1, 2020

As far as the send and receive commands and switching between them. right now all I have is line 1 having a receive command from port 2.
What are the odds that the voltage the scale is sending from (7-10v) would mess with the PLC?

OkiePC · Mar 1, 2020

It has been a long time since I did serial ASCII with a PLC and it was Allen Bradley. I had to monitor a bit for the serial port that told me that there was data and use that bit to trigger the receive logic. I am not sure what the equivalent would be for a Click, but I expect that it will be similar.

I am not sure about the voltage, but I would get a serial port isolator to be safe.

I have used the RS-485 isolators from this company for a long wire run to protect a PLC from surges and lightning and it has worked great:

https://www.serialcomm.com/serial_r...olator/rs232_3_wire.product_general_info.aspx

KirkC · Mar 1, 2020

Just to be sure... you do not need to put +5V on the Click. Do not connect that pin. You only need 3 wires: TX, RX, and SG. And jumper 7&8 on the scale.

jcollins · Mar 2, 2020

yes kirk I only have the 3 pins connected and not the 5v

gclshortt · Mar 2, 2020

I would put the scale in Key Mode. You get the serial output after pressing the PRINT key.
In the Recieve instruction, make sure that the protocol is set for ASCII. The default is Modbus. Ensure that the communication parameters are also the same. (Baud Rate, Data Bits, Stop Bit and Partity)
If no communication is being done then switch the RX and TX signal lines.

Here is a post using the serial with Modbus. Yours would be only receiving with ASCII protocol only.
https://accautomation.ca/click-plc-send-and-receive-instructions/

I hope this helps you out.
Regards,

Dravik · Mar 2, 2020

Have you tried using a computer and telnet just to test the rs232 first? I would double check that the scale is outputting data first before I tried to hook it to my PLC.

jcollins · Mar 2, 2020

that's my next step, order a converter cable today

Manglemender · Mar 3, 2020

Dravik said:
Have you tried using a computer and telnet just to test the rs232 first? I would double check that the scale is outputting data first before I tried to hook it to my PLC.

+1

Get yourself a terminal emulator program ( I use Putty) and ensure the scale is outputting something first. If you get nothing, try swapping pins 2 and 3 (Rx Tx).

https://www.putty.org/

I also use putty for SSH and also for TCP socket comms testing.

Nick

jcollins · Mar 3, 2020

So we got it working briefly last night and then we had to move around my work space for reasons...
Turns out I do need to connect the 5v to pin 6 on the DB9 connector. also this scale you don't swap the Tx and RX pins. I haven't worked on it since moving things around but was very much encouraged by what we discovered.

getting my click plc to communicate with a rs232 commercial scale

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