SX Proto Board and using a 4N25 as an input for the SX

Little_Part_Man

Hi, Every One

I looked at the Data Sheet for the 4N25
at web page http://gamma.octopart.com/Fairchild__4N35.pdf

The problem that i have is what value do I need for the resisters in the test circuit they have on there web page

·there are no values listed·I will be using 5 volt regulated as the input to the 4N25 an the SX input

Can any one help with this

·Thanks for any help that any one can give me



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·Thanks For all·the Help that You Can Give So that i can know·how to write SX Code


······································· Stefan

Post Edited (Little_Part_Man) : 9/17/2007 11:24:31 AM GMT

pwillard

You treat it the same as an open collector pin on a TTL chip. This means you need to do what it takes to bring the input pin on the Stamp to a logic "1" when coupler isn't active and "0" when the transistor turns on. You might try a value between 4.7K and 10K tied from the collector on the coupler to Vdd and 200 ohms from there to the Stamp input pin. The emitter on the coupler would be tied straight to logic GND (Vss).

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There's nothing like a new idea and a warm soldering iron.

Little_Part_Man

·pwillard

Thank You for your reply

I will give this a try and see what i come up with

Will i need a resister· from the base to emitter and if so

Just enough to get a logic "0" and logic "1" this what i am thinking

Please let me know if i am right about this or not

Thank You for your help

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·Thanks For all·the Help that You Can Give So that i can know·how to write SX Code


······································· Stefan

pwillard

You shouldn't need to bias the base pin. Leave that up to the LED in the opto-coupler.

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There's nothing like a new idea and a warm soldering iron.