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----- Original Message -----

From: Sudhaker Raj

To: Electronics_101@...

Sent: Tuesday, October 23, 2001 11:31 AM

Subject: [Electronics_101] Re: Switching and Dimming 120vac

I wana to add something from my earlier experience.

you should use pulse mode trigering for turning on the triac that way
it can handle. say pulse train of 2kHz with 10% duty cycle will be
great. use some transister as 2N2222 to power up the triac
triggering...

?? ?Actually, I was thinking along the same lines, using a 2N2222 to trigger a triac, so thank you for your input there. The opto isolators are an ideal I did not think of before but are definatly a good ideal.

as JIM said, EEPROM is not for that kind of circuitary. guess true, u
can always avoid this by a single decade counter chip with de-
mutiplxed output (10 seperate output changing state one by one) and
wire it for your desired sequence. why to use momory when U can build
this 3 or 4 bit memory by wires (hee hee...)... also U r not going to
program it very often, it will be one time JOB...

?

??? The pattern is not as simple as lights flashing in sequence, and the exact pattern may vary and have more than one light on at a time. I am making several of these circuts and?I have designed them to be programmable?by a user with no electronics knowlage. They can hook it to their computer and set a pattern for the lights using software I wrote. After the pattern is sent to the box, the computer can be disconected and the circut runs on its own. Curently, the circut controls LED's so I can see what was going on as I write the software.

OPTO-ISOLATOR is a great idea if u r willing to interface the DC
circuit with some other device... but if U want to make the whole
system stand alone, u can surely avoid them to make whole setup
cheaper...

---
Raj
--- In Electronics_101@y..., Jim Purcell wrote:
> yahoo,
>
> > I am working on a circut which uses a EEPROM made by Parallax to
> > animate a string of christmas type lights. I intend to have four
> > separate 120vac outlets that are switched on and off (dimming
would
> > be nice) by the EEPROM. Obviously, the outputs EEPROM can not
handle
> > much current at all.
>
> Memories of any kind are not designed to drive anything but other
circuits.
> In addition digital devices won't like AC. What you will need is a
triac for
> each AC device. In addition I would use opto isolators to couple the
> controlling signals to the triacs and probably buffers to control
the opto
> isolators.? An opto isolator is a device that uses some kind of
light source,
> usually LED's to turn on and off another device, like a transistor
or a
> triac, etc.? A buffer is a device that draws very little current
from the
> input device but can deliver larger current to the output device.
>
> Jim
>
> > I thought of using the EEPROM to control a small
> > relay and hook the contacts of the small relay to a coil of a
larger
> > relay to turn the light on and off, but I would like to use some
kind
> > of solid state circut to control the 120vac (that way I could
> > implement dimming). Any thoughts on how I can control the 120vac
with
> > a small current. Sorry I don't know the exact peak current the
> > outputs on the EEPROM can handle.
> >
> >
> > To unsubscribe from this group, send an email to:
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> >
> >
> >
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