Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

How to Drive Opto-coupler...

Status
Not open for further replies.

yusuf

Member
I guys I have an auto-coupler PC187 ..
And i have CMOS circuit which works on 8v ....
And with the help of this auto-coupler I want to switch my relay...
My relay is 12v and it consumes 100ma to work properly....

Thanks ..
 
It is called an Optocoupler, a PC187 ? are you sure it's not a PC817 ?
Is there a reason you want to use an optocoupler to switch a relay ?
It is not usually done this way.
 
Yaaa it is PC187.. and it has 4 pins...
I want to use this optocoupler to switch relay via transistor...

Can you provide me the detail with circuit diagram friend..
 
Last edited:
I have attched the circuit diagram...
Please have a look...

But while arranging like as in circuit diagram....
I am getting 6v at relay terminals....
and therefore the relay doesnt energize..

SO please help...
 

Attachments

  • drive.PNG
    drive.PNG
    10.1 KB · Views: 2,046
You have only ~ 1mA through the opto diode, so transistor T1 probably isn't turning on fully. Try reducing R4 to 2k2, or even 1k.
 
Hi alec thanks for your reply...

I am connecting pin1 of optocoupler to positive line... line of 8v...
And pin2 to negative line(in between the resistor R4 is available)

Pin3 to transistor via resistor for switching 12v relay..
pin4 to positive line of 12v supply..

But while changing the resistor R4 value (2.2k and 1k) the problem remains same..
It doesnt switches the relay...
I NOW ALSO GET 6v ON RELAY TERMINALS...

BY REMOVING THE 8V SUPPLY ....
NOW ALSO THE 6V IS APPEARING ON RELAY TERMINALS..

IN SHORT.... WHILE REMOVING OR GIVING 8V SUPPLY TO THIS OPTOCOUPLER, IN BOTH CONDITION I AM GETTING 6V ON RELAY ....
SO THIS 12V RELAY DOESN'T WORK...

PLEASE HELP FRIENDS..
 
Last edited:
It makes no sense to drive a relay coil with an opto isolator. The relay already provides isolation. Just add a transistor to drive the relay coil.
 
he gets noise resetting the circuit as he tries to switch the mains operated nearly 1HP motor on this relay contact. now the medium power transistor is under driven, thus suggesting to increase the base current.
 
Last edited:
Friends thanks for your replies ...
this problem has being solved now...
Thanks again...
 
Status
Not open for further replies.

New Articles From Microcontroller Tips

Back
Top