Hi Keith,

> Hi,
>
>    has anyone got a neat way to interface photodiodes to a pic? Ideally I
> would like to hang four of them on a 16C84 and still have some pins left to
> display the results.
>
> So far the best I have come up with is to use the photodiodes as current
> sources to charge a capacitor. Use a low leakage FETs to discharge the
> capacitors and  comparators to signal when the voltage exceeds a preset level.
>
> This involves quite a lot of components (capacitors, quad comparator, FETS,
> voltage reference) and isn't particularly easy  to set up. Has anyone found
> a neater and more linear solution?
>
> Keith

how about using 4 capacitors, one 74HC4066 (4 fet switches),
(or even better a 1 of 8 analog switch - the 4xxx family has it)
, one discharge resistor tied to one side of the switches and a single
comparator behind that stuff?

Hope it helps

Frieder


--
; Frieder Ferlemann
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