Hi,
I am trying to implement a isolation in between a serial communication system. One side its have a RS232-TTL(MAX232 circuit) level terminal & other side contains a 3.3V based microcontroller whose power is directly driven from a transformer less capacitor based power supply. I tried a setup a circuit that mentioned in the attached file ,but it doesn't helped helped me. Please help me to rectify the error in this circuit.
Thanks&Regards,
Geo
It looks to me like it should work.
You do know on the 16-pin MAX232 IC that, even though it's not shown on the schematic, you need to:
1) Connect Pin 16 to VCC (+5v)
2) Connect Pin 15 to GND
Also, the striped part of the capacitor symbols are the minus leads of the 10uF electrolytics.
One thing is , when I placed a CRO(for testing I used an isolated 3.3V supply) prob across the C-E pin of 4N35 in the Rx part (Also in RXD line), I can see some Sq.waves according to the Key press in the other terminal. This made me more confused.
So we need to replace the 4N35.? Whether MCT2E is suggested to do the job. Its tr is 5us@10V
One thing is , when I placed a CRO(for testing I used an isolated 3.3V supply) prob across the C-E pin of 4N35 in the Rx part (Also in RXD line), I can see some Sq.waves according to the Key press in the other terminal. This made me more confused.
So we need to replace the 4N35.? Whether MCT2E is suggested to do the job. Its tr is 5us@10V
If My memory is correct It worked well up to 57k baud but the radio I had would only talk to it at 4800 if I rember right. I did use it on another radio for the interface and it worked. I will verify this and let you know I need to look at the radio settings.
I did build an interface using the 4n35 and had problems with them. For some reason as I rember I just could not get them to talk. That is when I used this circuit.
If My memory is correct It worked well up to 57k baud but the radio I had would only talk to it at 4800 if I rember right. I did use it on another radio for the interface and it worked. I will verify this and let you know I need to look at the radio settings.
I did build an interface using the 4n35 and had problems with them. For some reason as I rember I just could not get them to talk. That is when I used this circuit.