Sign in to follow this  
Followers 0
tomcody

replacing the 6n138/139 optocoupler

7 posts in this topic

Hi everybody, in my country the 6n138/139 optocoupler is a little expensive and some times a hard to find component, and searching in the web I found an alternative circuit with the 4n26 or 4n36 (I tested it with both) - comes in PDIP-6 and this is the equivalent circuit for using instead of 6n138/139:

circuitoconel4n26o4n36erl7.gif

I'm not sure but if you look at the fairchild datasheet appears a lot of others optocouplers - maybe those works too.

Share this post


Link to post
Share on other sites

I use a 4n25, since that's the only optocoupler my local Maplin had. Never had any problems with it.

Share this post


Link to post
Share on other sites

Rasteri are you using the 4n25 as a drop-in replacement or what?

Unfortunately not - the pinouts completely different (for a start there's two less...) I've attached the circuit I'm using, I dunno if it's an optimal solution but it certainly works.

EDIT : My schematic was wrong, LyleHaze's is better (see below)

Share this post


Link to post
Share on other sites

Your pin numbers have 4 and 6 swapped.

This might confuse somebody that tries to wire this up.

This one has them corrected.

Also, this circuit should have a pullup resistor for

pin 5 (to RX). It might work without it, but for the

price of a resistor, why take chances?

Have Fun,

LyleHaze

3648_midiin2_png99fc9848e5fd983dd5057a7b

Share this post


Link to post
Share on other sites

fixed it, now are correct - I tried before a simple circuit like yours, but it doesn't works, I'll try your circuit. Thanks.

Share this post


Link to post
Share on other sites

*ahem* cross post.

very useful, though.  ;D

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0