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MAX3232: How to establish Communication between a Coulomb Counter and A Beckhoff PLC using MAX3232 chip

Nitish Mulye
Prodigy 10 points
Part Number: MAX3232

Hi,

I am currently working on an automation project where I have to  establish communication with a Coulomb Counter and a Bechhoff PLC. The Coulomb Counter uses the TTL protocol while the PLC communicates with the RS232 protocol. To convert the TTL to RS232 standard, we are using the MAX3232 Converter between the PLC and the Coulomb counter. The general idea is that the we want the read the State of charge of a battery which the coulomb Counter is connected to and send it to the PLC for further processing. Unfortunately I am having trouble with setting up the interface.

These are the links to the Devices we are using:

Coulomb Counter : 

https://www.mylithiumbattery.com/shop/other-accessories-for-lithium-batteries/charge-indicator-coulomb-counter/coulomb-counter/

TTL to RS-232 Converter :

https://www.pollin.de/p/rs232-ttl-wandler-mit-max3232-810358?utm_source=google&utm_medium=fshopping&gclid=EAIaIQobChMIt6rq35aX8gIVXAaICR119wLxEAQYAyABEgKB-PD_BwE

Beckhoff PLC : 

https://www.beckhoff.com/en-en/products/ipc/embedded-pcs/cx9020-arm-cortex-a8/cx9020.html

The Coulomb Counter automatically sends the data in the form of 18 Bytes long data packets every second in the TTL Proticol. For information can be found  here :

https://www.mylithiumbattery.com/wp-content/uploads/sites/2/2019/04/TTL232-CC-Comm-Specs.pdf

Unfortunately the TTL/RS232 converter is not detecting anything. I am trying to figure out if the converter need to be programmed some way or it needs to be calibrated somehow  as just connecting the wires properly together is not working. ANy suggestions would be helpful. Thank you

  • 0
    TI__Guru 52282 points

    Hi Nitish,

    Are you not receiving any output at all from the converter or are you not getting data to the intended destination without it being attenuated? 

    Have you measured the output signal from the Coulomb counter to ensure the signal is reaching the Max3232? 

    How long is the cable between the converter and the PLC? 

    What VCC is connected to the converter board - have you ensured it is reaching the IC on the chip? 

    So in theory this should work fine (depending on distance) - the converter board with the Max3232 on it looks like its designed okay. Have you tested this with any other converter board or just 1? The data-rate looks slow so i don't see issues there either. There could be issues with how that converter board was built - (not really in the design but maybe the board itself was manufactured). 

    So I'd suggest checking where the signal stop traveling - i.e. if the signal from the counter looks good but then the MAX3232 doesn't output anything its either an issue with the converter board or part (assuming TTL signal is read correctly  by MAX3232 - but I don't think thats the issue). If it does some to be around the converter board - if you haven't tried another converter board (same type - but fresh unit) I would also do that to see if it could be just a singular issue. 

    Please let me know the answers to the above questions to see if we can isolate the problem.

    Best,

    Parker Dodson