The LDR's that I used (square ~10mm x10mm) were far more sensitive to
incandescent than led (never tried the more exotic colors) and required
no tricky alignment. I just put them in a sleeve with the LDR leads
coming out of one end and the bulb leads the other,
The bulb sandwiched between the two (stereo)
The units were designed for line in/out insertion so getting the LDR
resistance down to a reasonable level didn't take much current.=20
I used 12 Volt lamps and never ran them at over 8 volts if I remember
correctly.
Over four years of making them I never had a bulb failure that I can
remember. I must have made 400 to 500 units
My customers were beach front caf=E9's who would be fined $$ for not
having a disco licence if the music was too loud (required to draw the
customers).
Sorry no PIC involved just a car alarm rx and keyring tx for the lookout
waiting to spot the inspectors making their nightly rounds=20
Just two levels, full or low level (user adjustable with a pot mounted
on the rx box)
The decay (if set to full mute) sounded like the normal fade out of a
song ending=20

> A quick 'n dirty way of remote controlling volume that I have used in
> the past (with great success) is to use an LDR (LDR's for stereo) with
a
> small 6Volt grain of wheat lamp sandwiched between them and shoved
into
> some cable insulation and driven direct from an I/O pin
>
> The attack /decay times are slow and are well suited for audio and the
> signal is also Opto isolated so no problem with earth loops.
>
> Because the response time is slow you could PW modulate the lamp at
very
> slow rate, 10Hz would be your lower limit

Is there any reason you didn't use an LED instead of an incandescent?
The
LED would take less current for the same brightness, is more rugged,
should
last much longer, and is probably cheaper.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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