On Mon, 12 May 2014 07:48:48 +0100, N_Cook wrote:

You used to be able to get neat simple "timer" buttons for stairway
lights, on for the duration of climbing a flight, but should work for
DC. They must have had a piston in a cylinder with a spring return. You
pressed down on the button to expel the air from the cylinder, a flap
valve closed and then air would probably be admittted along a long
capilliary tube , coiled up somewhere inside. Gave timing on of about 1
minute

Argh. Do they still make such timers? I used to use Agastat brand
pneumatic timers back in the 1960's. Agastat is now TE Connectivity:
http://www.te.com/en/home.html
It looks like they still make pneumatic timers:
http://www.te.com/catalog/bin/TE.Connect?C=15003&M=FEAT&P=173197&U=&BML=10576,16 354&LG=1
Amazing. Thanks for the memory jog.

Also, if you're into retro timers, there's also the thermal time delay
relay, usually built inside a vacuum tube envelope.
http://diyaudioprojects.com/Tubes/KT88-Push-Pull-Tube-Amp/6NO30-Thermal-Delay-Relay-Vacuum-Tube.jpg
http://www.ebay.com/sch/i.html?_nkw=6n030+delay

While these have both been replaced by the 555 timer and digital
equivalents, they're still fun to play with.
https://www.youtube.com/watch?v=ku91Yg2lJmk


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558