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Suggestions on analog galvanometer ?

Discussion in 'General Electronics Discussion' started by Externet, Dec 24, 2018.

  1. Externet

    Externet

    707
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    Aug 24, 2009
    Unless better options you may suggest; am after a
    [​IMG]
    as I have to glue a 15mm x 10mm x 1mm mirror to its pointer. Will be driven by a 7555 triangle wave repeatedly at 1 Hz. Scale and housing is irrelevant, unnecessary. Am after the movement only.

    Do you see an alternative way to make such a tiny and light mirror to oscillate 45 degrees endlessly at this comparatively minimal power consumption ?
     
  2. Bluejets

    Bluejets

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    698
    Oct 5, 2014
    Because of the weight/mass of the glass, I seriously doubt the movement shown would support it or indeed move the way you want.
     
    davenn likes this.
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    9,137
    1,846
    Nov 17, 2011
    At 1 Hz you could use a hobby servo but not at the small power consumption. The same goes for a laser scanner unit.
    You'll probably experience overshoot and undershoot at the peaks and troughs of the triangle as such a meter is usually only very likely damped (if at all) and will not be able to stop and revert direction of trvale immediately.
    Consider using a highly reflective polished piece of metal (aluminum foil) to get rid of the glass part of the mirror.

    Would you be willing to share with us what you want to achieve with your construction? Someone may come up with an altogether different idea to achieve the same effect.
     
  4. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Ayyyyyyyy Caramba ! . . . . . . . parace ser, que es Externet . . . . . . . NO Internet . . . . pero . . . . Externet !


    You got answers ? . . . . . . then I'se gots questions . . . . a la Rat Shack


    I have to glue a 15mm x 10mm x 1mm ***** mirror to its pointer.
    Do you see an alternative way to make such a tiny and light mirror to oscillate 45 degrees endlessly at this comparatively minimal power consumption ?


    That's definitely achievable by the utilization of silver mylar mirror film . . . . with the end result being as LIGHT as a popcorn fart.

    How you know dat I know dat?

    Well that happens to be because my first Projection Tee Wee of circa 1980-1-2-3 ? ish times, happened to be a Zenith that had the internal tri color CRT's feeding into attached lenses and then had all 3 reflecting onto and then off of a surface silvered mirror.
    Their images then ended upon the surface of a Fresnel lens backed translucent screen, of which you viewed that projected image
    on its other side.
    To keep from being such a big behemoth, the units top screen lifted straight up out of the cabinet console base via 4 corner, motor driven lead screws and retracted down into the cabinet during turn off / non use.

    My next generation replacement was being a BitsuMishi, and upon my need for its first inspection of the insides of the unit, I was shocked.
    That HEAVEEEEEE . . . .and that's cajone busting EEEEEE's . . . . plate glass surface silvered mirror, was instead, using an aged and kiln dried rectangular HARDWOOD frame that had silvered mylar mirror film wrapped around it and multi i i i i i i i stapled to the periphery of the frame, and they surely then finally used warm air to shrink the film surface, to then being as tight as a drum skin.
    Looking into it, it seemed as optically flawless and as reflective as the prior GLASS mirror was.
    Should you have access to one of the later generation mirrors saved, and you only need the 1 mm width aspect, I am sure that there was at least a 3/8 inch surplus of film that was outward from the staples .
    A single edge razor blade should be able to let you reach in and extract meters of that width, and the basic whole mylar mirror would be unaffected.
    OR . . . . .you should find that optical quality mylar mirror film being available on E- bay or Amazon.

    I would have to lab analyze their resultant exact differentialities, since I do know that two conditions that you encounter with light transmissivity might show up.. . .e.g. . . . .
    Direct sunlight . . . versus same sunlight passing thru a pane of window glass . . . . are not the same.
    Sunlight passing thru an optical glass lens to start a fire at its concentrated apex is superior to the use of a plastic fabricated lens element.


    I have to glue a 15mm x 10mm x 1mm mirror to its pointer.

    I can't perceive the three given dimensions . . . . . but seem to want to assign the 1mm to being a thickness dimension AND is also being the silvered surface.
    You will need to provide a rough sketch, as to how the mirror attaches to the meter pointer.
    Somehow I want to perceive of you wanting to duplicate some lab equipment which I have seen and used, in which it had a high intensity focused light slit that reflected off a d'arsenoval or taut band meter movement that projected that light slit image upon a translucent screen that you viewed from the other side. With some additional mirror bouncee--bouncee inside of the unit, you could get some fanta a a a a a a aster r r r r r rrific effective pointer length.
    You could press a finger into the meter support and faintly see it quiver to your heartbeat.
    The contrast of light on the translucent screen was a shortcoming in a well lit room . . . . . IMAGINE the use of a RED laser beam for illumination, instead !.

    I don't get the triangular waveform drive either . . . . . or else, considering that the meter pointer is limited to swinging 90 degrees of a 360 degree possibility.
    Could it be that you are combining a static fixed DC "trim" voltage and the triangular wave DC superimposed , so that the static DC voltage establishes meter "zero" center while the added / subtracted triangular transition extremes then give you a 45 degree swing, both directions from meter zero center, at that specified 1 Hz rate .

    BTW . . .with that being a Chinee meter movement, and not Triplett or Simpson, is its scale being
    1 ma or 100 ua full scale . . . . . . . . . . . or with my experience of choice galvanometers, with them being on down as low as 10 ua.

    Thaaaaaassssit . . . . .

    73's de Edd . . . . .
    . . . . . . . . . . . .





    ***** . . . relevance

    Here is a likewise, differently perceived situation . . . . . involving dimensional perspective . . . . .

    Two engineer trainees were standing at the base of a flagpole, looking at its top. A woman walked by and asked what they were doing.
    "We're supposed to find the height of this flagpole," said one, "but we don't have a ladder."
    The woman took a wrench from her purse, loosened a couple of bolts, and laid the pole down on the ground. Then she took a
    tape measure from her pocketbook, took a measurement, and announced, "Twenty one feet, six inches," and walked away.

    One engineer shook his head and laughed, "A lot of good that does us. We ask for the height and she gives us the length ! "
     
    Last edited: Dec 24, 2018
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  5. Externet

    Externet

    707
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    Aug 24, 2009
    Thank you, fellows.
    The first plan is to bend the pointer back crossing the pivot center and glue the mirror there. It is actually glass, first surface, gold coated, flawless optical quality perhaps (corrected) only 0.5mm thin ~half a penny thin. Nearly unobtanium, got 200 pieces. Cannot weigh it.
    Installing the mirror NOT at the pointer end as a 'flag' that would impair the movement on air resistance and momentum/inertia effects, but instead, in a manner similar to a carburetor 'butterfly', where mass is balanced on the mirror center line coaxial to the movement axis.
    A poor sketch follows, but may give some visual idea.
    A mylar type mirror may be lighter; but poor optics and distorted reflection due to its flexion is undesired. Will project a moving laser dot onto a far target.
    Yes, minimal power consumption is the driving force of this plan that should run on a single 18650 for 24 hours minimum, and other minor circuits powered from it.
    Another correction, may be about 2 Hz.
    Agree that 'galvos' are not a choice. A scanner moves too fast (bought and dissected one); its springy stiffener is not modifiable.

    Angle of sweep, undershoot and overshoot can be compensated with timing and amplitude of the driving triangle/sawtooth wave. I hope.
    Keep ideas pouring in...

    P1010803.JPG


    Edited. Only 45 degrees of the pointer movement of its ~90 degrees capability will be moving the mirror.

    [mod note: image resized]
     
    Last edited by a moderator: Dec 24, 2018
  6. 73's de Edd

    73's de Edd

    2,649
    1,076
    Aug 21, 2015
    NEVER . . . . would have interpreted that, with the sole initial info supplied.
    I don't think that you will have any success in the degree of reforming required to the original pointer needle of that unit.
    Probably, will need just a stub of the original needle and a conjoining of the aluminum support wire / or balsa of the added on mirror support mechanics.
    I also agree on its balancing out, as being respective to meter center pivot axis.
    Still think that your suggested mirror mass will be too great . . . I would still be leaning towards the lighter, optical quality mylar mirror film.

    73's de Edd . . . . .

    upload_2018-12-24_11-57-37.png
     
    Last edited: Dec 24, 2018
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