Re: Group Design

From	Chris <xxx.syseng.yyy@gfsys.co.uk>
Newsgroups	comp.arch.embedded
Subject	Re: Group Design
Date	2020-08-08 00:00 +0100
Organization	Aioe.org NNTP Server
Message-ID	<rgkmep$1p70$1@gioia.aioe.org> (permalink)
References	(6 earlier) <041d35fe-f5a5-4b7a-a78b-291104e34220o@googlegroups.com> <rgi24o$1has$1@gioia.aioe.org> <cc6f131d-e8e7-387a-fe5e-907478e75062@electrooptical.net> <rgje0v$g3r$1@gioia.aioe.org> <92461a49-9c5d-414d-b3f3-e98ec68b974bo@googlegroups.com>

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On 08/07/20 15:12, Rick C wrote:
>

> Efficiency may be personally important to an engineer who wants to overdesign everything, but this device has a 2 amp motor running off the 15 volts and it is all line powered, so no need to squeeze every last joule out of the design.  We are measuring some low level signals that could easily be disrupted by the switching currents.  So adding that type of a noise source would only be done if actually required.
>
> Oddly enough most of the power used in the electronics other than the motor are in the LED back lights for the low power LCD displays.  I have thought of using a switcher for them, but even at the 250 mA power level it's just not worth the hassle of dealing with the noise.
>
> Hmmm...  maybe that is a bigger impact than anyone here is thinking.  The display is on all the time.  The motor only runs at high power about half the time.  So it's really more like 1 amp.  Now the ratio is more like 4:1.  We don't have good data on the motor current, so no one has paid attention to the battery time.
>
> There are so many holes in this net.  lol
>
> BTW, does anyone understand what Phil Hobbs is going on about???  Why does he talk in code?
>

If you are switching a 2 amp motor load, then you already have more
problems than a point of use regulator, in terms of supply load step
function. If it's a dc brush motor, perhaps permanent magnet, that
looks like little more than 0 ohms, or nearly a short circuit at rest,
so you will need to ramp that up to limit current. Once spun up,
power is more or less proportional to load, but unless the data
sheet has all the info, you will need to build a mechanical test rig
to define the motor characteristics. I would do that anyway, to get
a idea of what size motor is needed and optimise the circuit
to drive it.

There's quite range of ic's for motor control, with soft start,
current limiting etc. You could perhaps use a brushless moter and
again, some ic choice on how that's done. Advantage is zero
commutator noise to upset other things. You really can't just use a
relay to switch that motor.

 > BTW, does anyone understand what Phil Hobbs is going on about???
   Why does he talk in code?

Iirc, if he will excuse the comment, Phil is a scientist, Science is
about math and numbers, measurement accuracy, whereas electronics,
once you get the theory  under the belt, as more about experience,
knowing what works, what doesn't and not a little intuition...

Chris

Thread

Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-07 18:46 -0700
  Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-07-07 19:02 -0700
    Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-07 20:36 -0700
      Re: Group Design David Brown <david.brown@hesbynett.no> - 2020-07-08 09:31 +0200
        Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-08 07:08 -0700
  Re: Group Design Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-07-08 14:13 +0200
    Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-08 07:19 -0700
      Re: Group Design Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-07-08 18:57 +0200
        Re: Group Design Theo <theom+news@chiark.greenend.org.uk> - 2020-07-08 18:28 +0100
        Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-08 11:12 -0700
          Re: Group Design Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-07-08 23:34 +0200
            Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-08 15:20 -0700
              Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-07-08 23:00 -0700
              Re: Group Design Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-07-10 10:09 +0200
              Re: Group Design Chris <xxx.syseng.yyy@gfsys.co.uk> - 2020-08-07 00:01 +0100
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-06 17:37 -0700
                Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-08-07 03:06 -0700
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-06 21:50 -0400
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-06 19:12 -0700
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-06 22:27 -0400
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-06 19:36 -0700
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-06 23:39 -0400
                Re: Group Design Chris <xxx.syseng.yyy@gfsys.co.uk> - 2020-08-07 12:30 +0100
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-07 09:57 -0400
                Re: Group Design Chris <xxx.syseng.yyy@gfsys.co.uk> - 2020-08-08 00:37 +0100
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-07 20:29 -0400
                Re: Group Design upsidedown@downunder.com - 2020-08-08 08:59 +0300
                Re: Group Design David Brown <david.brown@hesbynett.no> - 2020-08-10 15:43 +0200
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-10 09:18 -0700
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-07 07:12 -0700
                Re: Group Design Chris <xxx.syseng.yyy@gfsys.co.uk> - 2020-08-08 00:00 +0100
                Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-08-07 20:30 -0400
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-07 17:57 -0700
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-07 17:56 -0700
                Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-08-07 18:10 -0700
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-07 19:43 -0700
                Re: Group Design Dimiter_Popoff <dp@tgi-sci.com> - 2020-08-07 20:42 +0300
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-08-07 13:48 -0700
      Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-07-08 14:11 -0700
      Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-07-09 04:25 -0400
        Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-09 11:37 -0700
          Re: Group Design Paul Rubin <no.email@nospam.invalid> - 2020-07-09 11:54 -0700
          Re: Group Design Tom Gardner <spamjunk@blueyonder.co.uk> - 2020-07-09 20:02 +0100
          Re: Group Design Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2020-07-09 15:31 -0400
            Re: Group Design lasselangwadtchristensen@gmail.com - 2020-07-09 15:36 -0700
              Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-09 18:36 -0700
                Re: Group Design Clifford Heath <no.spam@please.net> - 2020-07-10 16:17 +1000
                Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-09 23:36 -0700
                Re: Group Design Stef <stef33d@yahooI-N-V-A-L-I-D.com.invalid> - 2020-07-10 10:22 +0200
      Re: Group Design David Brown <david.brown@hesbynett.no> - 2020-07-09 14:40 +0200
  Re: Group Design John Speth <johnspeth@yahoo.com> - 2020-07-09 07:59 -0700
  Re: Group Design Don Y <blockedofcourse@foo.invalid> - 2020-07-09 18:33 -0700
    Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-09 19:01 -0700
      Re: Group Design Don Y <blockedofcourse@foo.invalid> - 2020-07-09 22:32 -0700
      Re: Group Design George Neuner <gneuner2@comcast.net> - 2020-07-10 17:36 -0400
        Re: Group Design Ed Prochak <edprochak@gmail.com> - 2020-07-14 11:09 -0700
          Re: Group Design George Neuner <gneuner2@comcast.net> - 2020-07-16 00:26 -0400
  Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-09 22:48 -0700
    Re: Group Design Don Y <blockedofcourse@foo.invalid> - 2020-07-09 23:53 -0700
      Re: Group Design Rick C <gnuarm.deletethisbit@gmail.com> - 2020-07-10 01:15 -0700
        Re: Group Design Don Y <blockedofcourse@foo.invalid> - 2020-07-10 02:22 -0700

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