AC Signal Control
> On Sat, 24 Oct 1998 09:59:47 +0800 Starfire Zhu <CHEERFUL.COM> zhuxh
> >Hi, there!
> >Greetings to those who noticed this message.
> >Could you tell me the simplest way to control the AC signal? I mean I
> >want to switch the signal on or off with a I/O pin form my PIC. The
> >signal is kind of voice or low frequency. By the way, a solution with
> >relay is not expected, there must be other ways....
One very simple way not mentioned yet, is to use a LDR
and a light bulb
I have made many remote controled faders using this setup
(local cafe's who don't have a disco licence get fined if the music is
I use car alarm remote control (300mhz) units to turn on and off
a VERY small light(grain of wheat) bulb sandwiched between two LDR's
This way an employee standing outside/ across the road can lower
the music to a low level by pushing a button if they see the inspectors
comming down the street.
In my app a variable resistor also supplies power to the lamp
enabling the user to set the lower level(total mute not desired)
The atack is fairly fast though not disturbing and the decay is
almost like the end of a record, very smooth, your speakers
will love you,
I have only used LDR's on line signals (600ohms .5V)
and have had no problems.
Their resistance ranges from less than 30 ohms to over 20M ohms.
It takes around 4 seconds to reach 1M after removing the illumination,
email: her.forthnet.gr phone: + 3081 380534 cousens
snailmail: Folia, Agia Fotini, Karteros, Heraklion Crete, Greece.
Is it true that they have, on the new version of windows
managed to increase the MTBF from 95 to 98 minutes ?
(That's why they called it 95)
See also: www.piclist.com/techref/power.htm?key=ac
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