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'Opto output question'
2000\04\03@155110 by David E. Olson

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I'm never sure if hardware questions should be [OT]...so if it is, change
the subject line.

Pardon my hardware-challenged nature....

I've got an opto (6N135) that has a 8mA max output current. I need about
100mA (at 12v). I can't find (at least a readily available one) opto that
can do that. What's the best approach here? I'd rather not change the opto
and the circuit works fine - just need more current.

-DO

2000\04\03@155729 by John De Villiers

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use a suitable transistor and wire it like a darlington pair

{Quote hidden}

2000\04\03@160601 by David E. Olson

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Got it. I like when a plan is easy.

-DO

> -----Original Message-----
> From: pic microcontroller discussion list
> [PICLISTspamKILLspamMITVMA.MIT.EDU]On Behalf Of John De Villiers
> Sent: Monday, April 03, 2000 12:53 PM
> To: .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
> Subject: Re: Opto output question
>
>
> use a suitable transistor and wire it like a darlington pair

2000\04\03@162703 by Thomas C. Sefranek

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"David E. Olson" wrote:

> I'm never sure if hardware questions should be [OT]...so if it is, change
> the subject line.
>
> Pardon my hardware-challenged nature....
>
> I've got an opto (6N135) that has a 8mA max output current. I need about
> 100mA (at 12v). I can't find (at least a readily available one) opto that
> can do that. What's the best approach here? I'd rather not change the opto
> and the circuit works fine - just need more current.
>

Without details of the interface and WHY you think you need an OPTO,
I can only guess... but you may just need  a power FET.
(The small ones source/sink 1,000 mA.)

>
> -DO

--
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 |  __O    Thomas C. Sefranek  EraseMEtcsspam_OUTspamTakeThisOuTcmcorp.com
 |_-\<,_   Amateur Radio Operator: WA1RHP
 (*)/ (*)  Bicycle mobile on 145.41, 448.625 MHz

ARRL Instructor, Technical Specialist, VE Contact.
hamradio.cmcorp.com/inventory/Inventory.html
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2000\04\03@164353 by David E. Olson

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> Without details of the interface and WHY you think you need an OPTO,
> I can only guess... but you may just need  a power FET.
> (The small ones source/sink 1,000 mA.)

I'm using an OPTO because 1) I wanted to figure them out, 2) I need to use
them for another piece of this project (real noisy signal source) 3) I have
to make a 12v wave from a 5v wave.

The other piece of the project is the opposite - I need to take a 12v
hall-sensor output into my PIC and count the pulses. It all sorta smelled
like an OPTO opportunity.

-DO

2000\04\03@165825 by Thomas C. Sefranek

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"David E. Olson" wrote:

> > Without details of the interface and WHY you think you need an OPTO,
> > I can only guess... but you may just need  a power FET.
> > (The small ones source/sink 1,000 mA.)
>
> I'm using an OPTO because 1) I wanted to figure them out, 2) I need to use
> them for another piece of this project (real noisy signal source) 3) I have
> to make a 12v wave from a 5v wave.
>
> The other piece of the project is the opposite - I need to take a 12v
> hall-sensor output into my PIC and count the pulses. It all sorta smelled
> like an OPTO opportunity.

I find these answers honorable, but unjustified for an ISOLATOR.
Perhaps you have skipped the requirement for ISOLATION?
(A real noisy signal source is not usually a good reason for opto-isolation.)

Level shifting can be accomplished many ways.
Input level shifting down to 5 volts could be a resistive divider.

(And I like FETs for output level shifting.)

> -DO

--
 *
 |  __O    Thomas C. Sefranek  tcsspamspam_OUTcmcorp.com
 |_-\<,_   Amateur Radio Operator: WA1RHP
 (*)/ (*)  Bicycle mobile on 145.41, 448.625 MHz

ARRL Instructor, Technical Specialist, VE Contact.
hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org

2000\04\03@170847 by David E. Olson

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> I find these answers honorable, but unjustified for an ISOLATOR.
> Perhaps you have skipped the requirement for ISOLATION?
> (A real noisy signal source is not usually a good reason for
> opto-isolation.)

Well, in a way I considered the 12v to 5v a form of isolation (a stretch, I
know). Remember, I am hardware challenged. I'll accept honor over
justification anyway ;)

> Level shifting can be accomplished many ways.
> Input level shifting down to 5 volts could be a resistive divider.

Surprisingly, I know how to do that.

> (And I like FETs for output level shifting.)

That's where I start to fade. Haven't had enough experience to judge the
best possible solution and there are many times that software won't make it
happen. This is clearly one of them and I let commercial concerns do my
"real" hardware design - this one's for me and my tests.

-DO

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