Isolated RS-232 Serial Port
Cheap Isolated Interface for RS232 with maximum baud rate up to 9600
I was having a requirement to have an isolated RS-232 port since I was doing some High power control applications. This was my solution to the problem.
The circuit shows the ISO RS232 I built. Its quite cheap and handy. I tried to apply PC817 as well as MCT2E but nothing matches to 4N36.
You can however use the MCT2E version since the opto is cheaper than 4N36. Also PC817 gave an advantage of being smaller and available in SMD package.
For better transmission you require to configure a Pullup on the TX line of the Micro. Since the TX is in a Open-Collector(Pull Down) configuration to do the Inversion of the Serial Data.
The RX however does this automatically. The tested maximum baud rate Possible with this board using MCT2E - 9600 BAUD but with better optos of the 4N36 type this rate can increase.
For the Benefit of design I am enclosing the Zip file containing the whole Schematics & PCB for ISORS232.
Closeup of my working board with PC817 mounted & slot for MCT2E:
My High voltage system with the board connected to it:
Mera Bharat Mahan!!