Page 2 of 2 FirstFirst 12
Results 11 to 17 of 17

Thread: Analog scan rotator

  1. #11
    Join Date
    Mar 2008
    Location
    Sydney, Australia
    Posts
    315

    Default

    Hi imobscure, thanks for the info, this makes sense now. I will obtain the sin/cos signals from the crossed polarisers, then use the analog multipliers.

    Hi mixedgas, thanks for your kind offer. I am planning to use the analog calculation, because i think even 100us ADC-LUT-DAC delay would cause 3.6 degrees error at my target 6000 rpm, which is not acceptable.

    I will let you know if it works!

    weartronics

  2. #12
    Join Date
    Aug 2008
    Location
    St. Louis, MO
    Posts
    45

    Default

    You could use an angle encoder to clock a look up table to feed the sin/cos signals to your image rotator circuit. The home brew might work, but it I doubt it would work all that well at first, and the time to get it smooth would be daunting...

  3. #13
    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

    see attached zip

    there is NO delay, as these are MULTIPLYING DACS, they have the equavalent of a analog multiplier built in!

    will have to repost as I get:

    rotator.zip:
    Your file of 4.95 MB bytes exceeds the forum's limit of 4.00 MB for this filetype.

    Steve

  4. #14
    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

    resized file:


    ditch the cmos 4052 switch, they tend to fail with latchup problems, all it does is provide a inverted or non inverted x or y signal depending on the upper two bits.

    switching time is less then 1 microsecond on the dacs, but the signal path is true analog, so no delays

    Steve
    Attached Files Attached Files

  5. #15
    Join Date
    Apr 2007
    Location
    Costa Rica
    Posts
    523

    Default

    Quote Originally Posted by imobscure View Post
    You use the 4 quadrant analog multipliers to do the multiplication in the rotation formula. The sin/cos signale are classically (i.e. in my laserium days) provided to the circuit from a joystick moving in a circle. It could also be generated by a quadrature osc. or a look up table - I used to use a military surplus sin/cos potentiometer at one point - of course I haven't seen any of those for 25 years...
    I have a handful of NOS Bourns 50K sin/cos potentiometers - continuous rotation, no stops. PM me if you're interested. I'll see if I can find them - we can work something out.

  6. #16
    Join Date
    Dec 2007
    Location
    Stockholm, Sweden
    Posts
    551

    Default

    Thanks, that was a good and simple design!

    /d

    Quote Originally Posted by mixedgas View Post
    resized file:


    ditch the cmos 4052 switch, they tend to fail with latchup problems, all it does is provide a inverted or non inverted x or y signal depending on the upper two bits.

    switching time is less then 1 microsecond on the dacs, but the signal path is true analog, so no delays

    Steve

  7. #17
    Join Date
    Mar 2008
    Location
    Sydney, Australia
    Posts
    315

    Default

    Hi Steve, thanks for the design, that is interesting! Kind regards, weartronics

Posting Permissions

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