Optocoupler PC 817

[will7o20602]

Hi All ,

i'm totally new with optocoupler , so i need to use it nowadays with a microcontroller project to get a signal from the microcontroller and then control 12V contactor of a relay

Anyone can help me?

 

[Ian Rogers]

First you need to check the datasheet of the PC817 to see if it can drive said relay sometimes relay coils can take 100 mA+. Secondly! you need a resistor (@ 470 ohm) on RA pin.

 

[will7o20602]

i tried but it still not working. When i check there is 3.9 V on the 470 ohm resistor..

 

[ericgibbs]

i tried but it still not working. When i check there is 3.9 V on the 470 ohm resistor..

hi,
That very old type photo-coupler will not drive a relay directly, you require a drive transistor after the coupler.

EDIT:
Like this.

 

[Boncuk]

additionally to ericgibb's I suggest to use a 6N139 optocoupler for direct connection to an MCU I/O pin.

The 6N139 transmitter requires 1.5mA only, thus keeping current requirements for I/O ports to a minimum.

Boncuk