Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: electrically operated valves
Message-ID: <1989May12.155045.21724@utzoo.uucp>
Organization: U of Toronto Zoology
References: <23526@shemp.CS.UCLA.EDU> <11170007@hpfcdj.HP.COM> <2011@randvax.UUCP>
Date: Fri, 12 May 89 15:50:45 GMT

In article <2011@randvax.UUCP> lacasse@blaise.UUCP (Mark LaCasse) writes:
>what I would like and can't find are PROPORTIONAL valves
>of some sort.  Something like a gate value with a stepper
>motor attached...

Good proportional valves are probably much more expensive than simple
on-off valves, since the market is much smaller.  As was suggested a
while ago when this came up, one thing you can do is combine several
on-off valves in parallel, with flow restrictors, to build a hydraulic
digital-to-analog converter; it's not true proportional control but it
might be close enough.
-- 
Mars in 1980s:  USSR, 2 tries, |     Henry Spencer at U of Toronto Zoology
2 failures; USA, 0 tries.      | uunet!attcan!utzoo!henry henry@zoo.toronto.edu