Wichit Sirichote, wichit.sirichote@gmail.com

Build a tester for MAX232 chip with simple circuit and USB powered.

This tester is for MAX232 16-pin DIP package. The tester will test the funtioning with loop back method for both TTL and RS232 logics. The tester was made with universal PCB, 40-pin ZIF socket, and some passive components.

The circuit is simple by making the MAX232 chip to be RS232 level conveter. All 16 pins of the MAX232 chip are wired to the 40-pin ZIF socket. The loop back test for TTL side is at pin 9 and pin 10. The RS232 level will be pin 7 and pin 8. We can connect the tester to the PC COM port and use serial test software to check its functioning easily.

The loop back test for RS232 side is at pin 14 and pin 13. SW2 provides TTL logic transition between logic '1' and log '0'. The receiving bit at pin 12 drives TTL logic indicator using a 3mm green LED.

SW1 is push/lock for powering the circuit from USB +5V power supply.

Testing steps:

1. Ensure the tester is powered off.

2. Insert MAX232 chip to the ZIF socket.

3. Push SW1 to turn power on.

4. Push test button and check the green LED.

5. Test the serial data stream with COM port tester.

When we press keys (Green), it will echo back to terminal in Yellow.

6. Push SW1 to turn power off.

7. Take the chip out.

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18 September 2016