[SOLVED] 6n137 optocoupler testin

[sabu31]

6n137 optocoupler testing

Hi
I am trying to isolate microcontroller pwm from power circuit using 6n137 optocoupler. The circuit diagram is attached. When i am testing using function generator. I am not getting any output pulses. Vcc=5V, Function generator output 5V square wave , 50Khz. Function generator ground is seperate from Vcc ground.Could some one tell me whats wrong with circuit or how do i test the optcoupler. Thanks in Advance

 

[alexan_e]

Pin7 (Ve) in the input to an NAND gate, you should connect it to 5v (High)
Pin6 (Vo) is the output but it is an open collector output, this actually means that the transistor can only ground the output or leave it floating
so to get a switching voltage you should connect a pullup resistor from Vo pin to the positive power supply (5v).
Check page 7,8 of the datasheet www.fairchildsemi.com/ds/6N/6N137.pdf

Alex

 

[sabu31]

Pin7 (Ve) in the input to an NAND gate, you should connect it to 5v (High)
Pin6 (Vo) is the output but it is an open collector output, this actually means that the transistor can only ground the output or leave it floating
so to get a switching voltage you should connect a pullup resistor from Vo pin to the positive power supply (5v).
Check page 7,8 of the datasheet www.fairchildsemi.com/ds/6N/6N137.pdf

Alex

Hi

I connected pull up resistor of 350 ohms.The circuit is working now. But still voltage output of pusles is of 3.5 Volts instead of 5 V (Vcc).

 

[FvM]

But still voltage output of pusles is of 3.5 Volts instead of 5 V (Vcc).

Seems to indicate an additional output load, by specification of the part, the open collector leakage current is < 1 uA.

 

[sabu31]

Hi

I am sorry, I could not understand by the "additional load". How do i isolate the problem.Thanks

 

[sabu31]

Hi

The problem was that i had a driver IC connected to the opto which was loading the opto (as the driver IC was non powered).