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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 1st Nov 2017, 9:10 am   #1
Join Date: Feb 2006
Location: Marlborough, Wiltshire, UK.
Posts: 281
Default One shot timer

Sometimes a one shot timer is very useful, for example to control a heater or battery charger which you might forget to turn off. Another thread mentioned an old kettle with no automatic off for example.
This old idea ( not mine, I think I saw it on the SMVP0 website ? ) may not suit the kettle but is useful elesewhere.
Simply put, modify one of those plug in timers with the push in segments so that the "clock" motor is powered from the output side, not the input.
Then set the segments for the time reqd, turn the dial till it just comes on and away you go.
On the timers I have done, it was obvious what needed modifying once it was opened.

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Old 1st Nov 2017, 9:26 am   #2
Nickthedentist's Avatar
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 13,545
Default Re: One shot timer

Useful trick, Ken.

On the Smiths (etc.) ones with pins which are inserted in holes do programme the on/off times, you can of course just fit the pins in the OFF holes which has the same effect.

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Old 1st Nov 2017, 2:48 pm   #3
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Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 5,674
Default Re: One shot timer

That's quite cunning! And good because once it 'trips' the mains is removed from the supply-side of whatever you're powering.

I did have something similar a while back - a NiCd battery-charger with a charge-timer where the mains supply came through a relay. You put the batteries-needing-charging in the thing then pressed the 'start' button which briefly connected the batteries to the relay-coil which pulled-in applying mains and starting the countdown-timer as well as latching the relay. When charge was complete the timer de-energised the relay, cutting off the mains.

I forget who made this but I liked it because once the batteries were charged the mains was removed from the charger primary-side, unlike a lot of cheaper NiCd chargers where the priomary remains powered when the charge-cycle is complete.
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Old 1st Nov 2017, 9:47 pm   #4
Herald1360's Avatar
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 11,645
Default Re: One shot timer

I fitted my work desoldering bench with one of the pin type. It's simply used to stop stuff being left on overnight. There's an OFF pin at 6pm and that's it. When the kit is first needed (not necessarily every day), you simply use the manual ON override. If you forget to turn the individual tools off after use it all goes off at 6 and stays off till the next override. Not 100% idiot proof- the idiot may be working late- but a cost effective expensive bit preserver!
.=.( _---\__|___|_---_)
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Old 2nd Nov 2017, 3:35 am   #5
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 374
Default Re: One shot timer

Being somewhat forgetful and easily distracted at times, I built a timer unit that turns everything off if you don't hit a reset button every 30mins.

There is a warning buzzer that sounds a few minutes before everything goes off.

It was a project in one of the Oz electronics mags many years ago.

Haven't installed it since we moved some 8 years ago though - I forgot which box I put it in and there's way too many boxes.
Terry VK5TM
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