Page 2 of 2 FirstFirst 12
Results 11 to 14 of 14

Thread: General Scanning Galvo?

  1. #11
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
    Infinitus Excellentia Ion Laser Dominatus
    Join Date
    May 2007
    Location
    A lab with some dripping water on the floor.
    Posts
    9,890

    Default

    Quote Originally Posted by Ed Wesly View Post
    So it's possible that this is a '70's vintage device?
    Its a 1960s device modeled off a 1949 servo valve actuator. The design has been continually improved.

    Go over to the patent server and look at patents by Montagu assigned to General Scanning.

    Steve

    - - - Updated - - -

    Quote Originally Posted by Ed Wesly View Post
    So it's possible that this is a '70's vintage device?
    Its a 1960s device modeled off a 1949 servo valve actuator.

    Go over to the patent server and look at patents by Montagu assigned to General Scanning.

    Caution, Hours of fascinating reading may result.

    Steve

    - - - Updated - - -

    [
    Caution, Hours of fascinating reading may result.

    Steve
    Qui habet Christos, habet Vitam!
    I should have rented the space under my name for advertising.
    When I still could have...

  2. #12
    Join Date
    Nov 2005
    Location
    Chicago, IL
    Posts
    64

    Default

    Holy flying spot scanners, Batman! I didn't know this Monatagu cat was active in the mechanical television era! Lots of fascinating reading...

    Here's how far I have progressed, thanks to all your help! I have one of those $90 Chinese RGB lasers impinging on the scanner, and the Spectra=Physics mirror device whirring away.

    Click image for larger version. 

Name:	ScanSetUP.jpg 
Views:	27 
Size:	237.1 KB 
ID:	42465

    The bass speaker output of a cheesy Jensen sound system was amplified by a 386 run off a 9v battery. Surprisingly gives the deflection I need!

    Here is a picture of the scan. The RGB beam has passed through a low frequency diffraction grating to multiply the fun.

    Click image for larger version. 

Name:	Scan.jpg 
Views:	36 
Size:	429.1 KB 
ID:	42466

    The photo above was made as the mirror scanner was slowing down after it was turned off. When it is running, it is way too fast to make oscilloscope-like sweeps, even if I slow it down with a Variac.

    Click image for larger version. 

Name:	Motor.jpg 
Views:	25 
Size:	238.3 KB 
ID:	42467

    So my next question I need help on is how do I slow this motor down to a few hundred rpm? I was thinking of making a 555 pulsed circuit a la Forrest Mims and have that drive a solid state relay. Or am I barking up the wrong tree?

    Thanks for all the help!
    I know what I want and I know how to get it
    I want to destroy passersby! - Sex Pistols

  3. #13
    Join Date
    Apr 2007
    Location
    Costa Rica
    Posts
    523

    Default

    That is beautiful! You're gonna need some kind of SCR circuit to have speed control with that 60HZ AC motor. You could build something from designs found online or go to Harbor Freight Tools and look into a router speed control. A light wall rheostat might work but the motor may get hot or hum loudly. This kind of basic experimentation can yield just as much satisfaction as tinkering with more sophisticated (expensive) systems. Keep working at it and posting results!

  4. #14
    Join Date
    Nov 2005
    Location
    Chicago, IL
    Posts
    64

    Default

    I finally found the time to return to this project and finish it. What was needed was a way to slow down the supermarket checkout scanner to match its sweep rate to that of an oscilloscope set up to look at audio frequencies, like 1 millisecond per division, or 10 ms per sweep. Six facets on the scanner add up to 60 ms per rotation, or about 16 rpm, about a factor of 100 times less than the free-running 1550 rpm of the motor!

    Being dimly aware that toy train locomotives could be made to crawl by using Pulse Width Modulated DC, I decided to build a circuit to pulse width modulate the AC going to the scanner motor. Doing some research on-line I found that it was discussed, but no details except that it required kHz of modulation. So I built a circuit using a 558 quad timer as a fully adjustable pulse generator following The Forrest Mims Engineer’s Notebook on a Radio Shack Electronics Learning Lab to switch a solid-state relay. Surprisingly it worked!

    Here is the demo done in the electronics lab, with a Lionel toy train transformer supplying the sine wave to the vintage galvo scanner. The scanner could take all of the 12 Volts the transformer could deliver!

    Click image for larger version. 

Name:	LaserOScope.jpg 
Views:	23 
Size:	274.4 KB 
ID:	43529

    The motor does get hot, but I don’t run it that long, just enough for demos. I will include a fan when I get around to building an enclosure for it. Here it is sitting on legs purring merrily along with 20 mW of Compass 215M green with the galvo.

    Click image for larger version. 

Name:	Web.jpg 
Views:	29 
Size:	167.5 KB 
ID:	43530

    This laser scanner adds to the MWK two-axis scanner take-out from a Video Disc player I’ve had fun with for decades!

    Click image for larger version. 

Name:	ScanWallWeb.jpg 
Views:	21 
Size:	201.8 KB 
ID:	43531

    Thanks for all the help! This kept me busy and out of trouble!
    I know what I want and I know how to get it
    I want to destroy passersby! - Sex Pistols

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •