[simpits-tech] Using real instruments

[Craig Rochester]

That's correct for the serial servo controller I'm using: 8-bit is a bit
rough for this.  I think a 12-bit controller,
1/4096 x 50,000' = 12' resolution would do it.  I don't know the limits of
PWM and servos regarding resolution...anyone want to jump in?

Craig R.

-----Original Message-----
From: simpits-tech-admin@simpits.org
[mailto:simpits-tech-admin@simpits.org]On Behalf Of Brian Sikkema
Sent: Sunday, January 26, 2003 9:19 PM
To: simpits-tech@simpits.org
Subject: RE: [simpits-tech] Using real instruments


Er, am I reading this wrong or do you only have ~300' resolution? I would
think that would be a tad... rough... might work for SPACECRAFT ;) but I
wouldnt want an aircraft altimeter that only showed me my altitude in steps
of 300'.

Brian


----Original Message Follows----
From: "Craig Rochester" <johncraigroch@msn.com>
Reply-To: simpits-tech@simpits.org
To: <simpits-tech@simpits.org>
Subject: RE: [simpits-tech] Using real instruments
Date: Sun, 26 Jan 2003 21:00:35 -0500

Rod, good point about the servo!

I haven't hooked my mod to my servo driven regulator yet, so I can't say how
it'll perform.  I do know I'm using a 8-bit controller so my resolution is
1/256 x 50,000' = 313'. So if the servo is "twitching" between digital bits
that's 300' of twitch.

Craig R.

-----Original Message-----
From: simpits-tech-admin@simpits.org
[mailto:simpits-tech-admin@simpits.org]On Behalf Of Rod Dale
Sent: Monday, January 27, 2003 12:20 PM
To: simpits-tech@simpits.org
Subject: Re: [simpits-tech] Using real instruments


I tried that - the normal movement of the bellows during vacuum operation is
so very small that one slight twitch or movement of the servo took me from
0ft to 9000ft !! If you could gear the servo right down it may work, but
servos have a habit of "twitching" which can cause big problems. You also
need to modify the servo so it's continuous rotation, with a method of
counting the rotations.
Rod

----- Original Message -----
From: Gene Buckle <geneb@deltasoft.com>
To: <simpits-tech@simpits.org>
Sent: Friday, January 24, 2003 7:14 PM
Subject: RE: [simpits-tech] Using real instruments


 >
 > > Ok, I bought the Altimeter.  I took it apart(a delicate task).  It
could
 > > definitely be driven by vacuum, but I'm going to try to modify it to be
 > > driven by pressure.  The ASTEK meter I have works by the expansion of
two
 > > sealed metal bellows expanding as the atmospheric pressure decreases at
 > > higher altitudes.  I'm going to drill a hole in each bellows, port
them,
and
 > > try pressurizing the bellows.  In theory this will be equivalent to
applying
 > > a vacuum to the outside.  If it works I'll post pics of the results.
 > > Otherwise...anyone interested in a ruined Altimeter? :)
 > >
 > You might also think about connecting a servo to the bellows and moving
it
 > that way.
 >
 > g.
 >
 >
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page.  Thanks!
 >

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