Re: Battery powered switch

From: John Crighton (john_c_at_tpg.com.au)
Date: 08/20/04 

Date: Fri, 20 Aug 2004 14:29:29 GMT

On Thu, 19 Aug 2004 12:42:10 -0500, James
<ltffekblpddw@mailinator.com> wrote:

>John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote in
>news:0syYdzD7OOJBFwTc@jmwa.demon.co.uk:
>
>> 2. Buy a short-range radio transmitter and matching receiver, the
>> receiver being configured for very low current consumption when idling.
>> You would need to add a relay or FET to do the on/off switching, as for
>> option 1.

>>Thanks John,
>
>Any thoughts as to where I can find a receiver like this?
>
>James
>

Hello James,
following on from John Woodgate's suggestion, perhaps you
could buy a wireless push button door bell from your local
hard ware shop. Find one for nothing, look around garage
sales, car boot sales, junk shops etc.
Open it up and silence the ding dong part if you like.
Fit a relay to give a contact closure when the remote
push button is pressed. A momentary contact closure
is fine also.

Use the momentary contact closure to operate a toggle circuit
or flip flop circuit so that you get another relay to switch on or
switch off.

Press the bell push button and your radio switches on and stays on.
Press the bell push button and your radio switches off and stays off.
A push on/ push off arrangement.

Have a look at some of toggle circuits from Terry Pinnell's site
http://dspace.dial.pipex.com/terrypin/Images/ToggleMoment.gif
http://dspace.dial.pipex.com/terrypin/Images/SimpleToggle.gif

Here is another on/off latch at the bottom of the page.
http://www.discovercircuits.com/PDF-FILES/4013oneshots.PDF
The output is on pin 13.
Have a look at the circuits on Terry's site and see how pin 13
can be made to switch a transistor to switch a relay, similar to this
http://dspace.dial.pipex.com/terrypin/Images/RelayToggle.gif

Maybe you could power your radio from an old car battery
that you can find for free lying around. Something that is no
good for starting cars but will work for months powering
a radio. A brick sized sealed lead acid battery would be
neater and cleaner if you can find one. Do some scrounging
that is what we hobbyists are good at. :-)

Regard,
John Crighton
Sydney