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I am trying use a HMI display with arduino NANO. I am powering arduino and hmi display ( topway 5 inch smart display ) with 9 volt adaptor. everyting works fine. but if I plugin the Tx, Rx pins which are coming from rs232 ttl converter (this device) to arduino nano's Rx and Tx pins, arduino nano is starting heating. I have waited one day heating was not to much but there was a heating issue. Also there is no problem communication between arduino nano and hmi display. If I plug out the rx and tx pins, there was no heating even after one day waiting. everythings looks fine. I guess that heating will make a problem in future within long term usage.

also if I powering rs232 converter with 5 volt, this time rs232 converter heating too much and broken. Therefore, I am powering rs232 converter with 3.3 volt. if I powering 3.3 volt there is no heating on rs232 converter.

this is my circuit diagram, sorry about my paint skill.

enter image description here

well, I didnt understand why arduino nano heating and how to fix that. Can you help me

mehmet
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    Are you sure the TTL and RS232 side were connected correctly? And if that is a 3.3V MCU, then obviously the TTL-RS232 converter **must** be used with 3.3V supply. Regarding the wiring diagram, the black wire of the display goes via the TTL-RS232 converter, that may not be a good idea. – Justme Dec 02 '21 at 19:16
  • @Justme connection is right, you can check from rs232 product page (link above) and also I have tried and there is no problem data send and receive. the black wire, actually ı made pcb all grounds are poligoned. so all gnd is same. I dont think so it make heating. – mehmet Dec 03 '21 at 06:18

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The Nano uses a 5V MCU (ATMega328). If you are going to connect it directly with the SP3232 then it should operate from the same supply or have a voltage translator between.

The SP3232, if it is genuine (doubt) should withstand up to 5.5V. That's not a lot of margin between that and 5V and you have routed the 500mA max current from the display through the RS-232 adapter board, which is bad. Run the ground wire from the display back to the supply directly. You don't need another ground wire to the adapter, there is enough noise margin in the RS-232. I have seen similar genuine chips fail from minor disturbances in the supply, they are not as robust as the old 5V-only MAX232 chips.

Spehro Pefhany
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  • well I will try to make a simple 20k/10k voltage diveder, I will informd you. Also you are totally right The SP3232 is bad***. but I didnt find any rs232 converter like that pcb on internet. generally all rs converter has db9 header like that https://nettigo.eu/products/max3232-rs232-ttl-converter – mehmet Dec 03 '21 at 06:23