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Light switch warning indicator

M

M.Joshi

Jan 1, 1970
0
Franc said:
I am trying to design an audible/visual indicator that beeps every 5
minutes when a light switch is turned on.

The complete circuit has to fit behind a light switch plate and so a
transformer cannot be used.

This can't be done unless you have a neutral at the switch position
When
the switch is on there is no potential difference between th
terminals
therefore no power source.

What about using a dimmer switch set to about 90% duty cycle? The
circuit could grab some power during the 10% off time.

- Franc Zabkar


This is not being built for a blind person - This light switch ofte
gets left switched on all the time as it controls a light outside.

It already has a neon light on it which seems to dim when the light i
switched on?

If I build the circuitry into a separate box next to the light switch
is there an easy way to sense when the switch is on/off
 
D

Dave Plowman (News)

Jan 1, 1970
0
If I build the circuitry into a separate box next to the light switch,
is there an easy way to sense when the switch is on/off?

In the UK lighting switches are usually single pole, so if that's also the
case in the US change to a double pole one and use one pole for the
sounder.
 
M

Mr Fixit

Jan 1, 1970
0
Dave Plowman (News) said:
In the UK lighting switches are usually single pole, so if that's also the
case in the US change to a double pole one and use one pole for the
sounder.

--
*If at first you don't succeed, redefine success.

Dave Plowman [email protected] London SW
To e-mail, change noise into sound.
why not use one of the movement sensor type lights
 
F

Franc Zabkar

Jan 1, 1970
0
This is not being built for a blind person - This light switch often
gets left switched on all the time as it controls a light outside.

It already has a neon light on it which seems to dim when the light is
switched on?

The neon is probably wired across the switch contacts. When the switch
is off the neon sees the full mains potential. When the switch is
closed the potential is zero.
If I build the circuitry into a separate box next to the light switch,
is there an easy way to sense when the switch is on/off?

Here's my suggestion:
http://www.users.on.net/~fzabkar/WarnLight.JPG

- Franc Zabkar
 
J

James Sweet

Jan 1, 1970
0
US light switches are electrically identical to UK switches, single
pole. The exception being the "4 way" switch which is placed between two
SPDT "3-way" switches in the rare occasion that a light needs to be
controlled from more than two locations.
 
D

Dave Plowman (News)

Jan 1, 1970
0
US light switches are electrically identical to UK switches, single
pole. The exception being the "4 way" switch which is placed between two
SPDT "3-way" switches in the rare occasion that a light needs to be
controlled from more than two locations.

Same as the UK, then. However, over here, identical looking switches are
available in double pole for things like water heaters, and using one of
those to also switch the sounder would IMHO be the simple way.
 
M

M.Joshi

Jan 1, 1970
0
Dave said:
In the UK lighting switches are usually single pole, so if that's als
the
case in the US change to a double pole one and use one pole for the
sounder.


US light switches are electrically identical to UK switches, single
pole. The exception being the "4 way" switch which is placed betwee
two
SPDT "3-way" switches in the rare occasion that a light needs to be
controlled from more than two locations.

Same as the UK, then. However, over here, identical looking switche
are
available in double pole for things like water heaters, and using on
of
those to also switch the sounder would IMHO be the simple way.

--
*If love is blind, why is lingerie so popular?

Dave Plowman [email protected] London SW
To e-mail, change noise into sound.


Using a double pole switch is an excellent idea - provided that the tw
poles are isolated.

Are these available in standard switch backplate fittings as the wate
heater ones tend to be slightly deeper?

I don't really want to go to the hassle of changing the existing ligh
to a PIR sensor type. Also, the neighbour's back door is very close s
it would trigger every time they stepped outside
 
D

Dave Plowman (News)

Jan 1, 1970
0
Using a double pole switch is an excellent idea - provided that the two
poles are isolated.

Not much point in them if they're not. ;-)
Are these available in standard switch backplate fittings as the water
heater ones tend to be slightly deeper?

In the UK they'll fit a 25mm deep box - but not IIRC a plaster depth one.
Although this might vary with make.
 
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