Current issue in arduino rs232

Thread Starter


Joined Mar 18, 2022
I am using arduino pin 2(rx) and pin3 (tx) and connection it to rs232 to ttl converter and 5 other digital pins which draw 35mA as total and arduino consumes 40mA seperatly.
now when supply is given, more current(approx 94mA) is drawn by the converter . Once I send/Recieve data, then Current drawn by converter decreases to approx 17mA. Now due to sudden increase in current on starting, arduino starts to heat at the place where voltage regulator is kept. Now I know that this is probably because of more current passes to regulator.
Should I put 330 ohm resistor between rx/tx pin to limit the current between converter and arduino??


Joined Jan 15, 2015
While for an Arduino Uno just as an example the chip's ( ATmega328P) data sheet covers 40 mA / pin most suggest a load not to exceed 20 mA/pin. If the 5 volt reg Vout drops due to excessive current draw the chip likes to do a reset. Also if the regulator runs hot it obviously is not good. Can you place a current limiting resistor in the circuit but then under normal operating conditions that resistor will have a voltage drop. Less seeing a circuit schematic I can figure this much. With a current of 17mA using a 330 Ohm resistor the drop will be I * R so 330 * 0.017 = 5.61 volts so I have no idea what you have in mind? This would go much better with a schematic, even hand drawn, and a data sheet for your rs232 ttl converter.



Joined Mar 10, 2019
If using the 5V regulator, what is the input voltage? The higher the input voltage, the more heat the regulator will create. The Arduino maximum recommended voltage is 12V, and that assume a good clean 12V supply (not a wall-wart type of supply). Best to use 8V to 9V to feed the Arduino regulator, it will generate less heat. You are not drawing all that much current, 100mA total current is well with specifications.


Joined Apr 11, 2010
There are many different models of the Arduino and there are slight variations in the specs. The most common model when someone says “Arduino” is the Arduino Uno Rev. 3. Is this what you’re using? It definitely makes a difference.