I will be using the optpto you suggested. For the opto the tech sheet
suggested the led voltage is 1.2 V @2mA it actually says a maximum of 3mA,
and we will say the regular LED is 1.7V at a total of 2.9V led voltage drop.
So I guess 200 ohms should be good, I just dont want to blow anything. I
will remodify the schematic and repost it by 6:00 est.

Thanks
Mike


> I agree partialy
>
> The led in the opto is drawn reversed
> diagram with external led is
>
> pic pin--------[Resistor]---->|------>|-------gnd
>
> current depending on optocoupler probably around 10 ma
> however , forward drop in led's is generally between 1.5 and 1.7 volt (at
> currents of a few ma)
> for a 5 volt supply of the pic we have on the resistor 5-1.5-1.5=2 volt
this
> gives an r of 2/0.01=200 ohm
>
> Be aware that with a single transistor optoisolator the ratio between
input
> and output current (current transfer ratio) is usually less than 100% (you
> send more current in than you can switch).
>
> What I would do is test your camera by wiring a resistor in series with a
> switch on the shutter input and checking with how high of a value resistor
> the camera reliably snaps a picture, then measure the current thru the
> resistor so you have an idea about what you need. start with 1 kohm or so
> and keep halving it down 5k,2k2,1k5 etc in subsequential steps.
>
> Kind regards
> Peter van Hoof
>

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