Holo Projector Servo Test

I’m definitely getting into the fun part of the project. I spent part of the evening trying to add a servo to the front holo projector. It was a little more tricky than I thought it was going to be. I’d seen photos and vaguely remember a setup on one of the tables at C4, but until tonight I didn’t understood the nuances of the angles and forces need to move something with a servo, so it was frustrating and fun at the same time.

Most people seem to use the same basic method to move pie panels, doors, holo projectors etc. And that’s to convert servo rotation into a linear movement using a push rod attached to the servo horn.

I’d bought some random mini servos from Tower Hobbies a while ago (Hi-Tec HS-55), and a push rod/linkage assembly from ebay. Problem was the servo was too small to fit the rod attachments. I managed to improvise and this is what I finally came up with

Please ignore the kinks in the rod, it really should be straight, but I’d tried to copy what I’d seen at C4 and got it totally wrong 😀

If I was to do this again I’d probably skip the pre-made assemble and make something in acrylic and parts from the local hardware store.

I also created a short video to summaries and demo the new setup.

As I explain in the video it’s not perfect, and I need to affix the servo more permantely to the dome rather than using velcro and I’m not entirely confident the linkage to the back of the HP will last very long.

The good news the Hi-Tec servo is definitely powerful enough to move the HP and will probably work for the pie panels as well.

I also need to decide if I’m going to add some code to my micro-controller to automate random movement.

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Posted by Chris on April 29th, 2008 in Dome, Electronics, Events, Legs | 14 Comments

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14 Responses

  1. Dan remarks on April 30th, 2008 at 5:12 am

    Instead of Velcro, you may want to look at teh quick lock fasteners from radio shack. They pull apart like Velcro but they can hold a lot more. If I remember correctly it was 20lb per square inch. I use to use them to hold network print servers to the sides of printer that did not have shelves and were suspended in mid air.

  2. Chris remarks on April 30th, 2008 at 11:28 am

    thanks. do you have a link to the product on the RS website? i took a look but couldn’t find it.

    cheers
    chris

  3. Dan remarks on April 30th, 2008 at 12:28 pm

    I looked for it, but couldn’t find it. i know I have some at home. I will get the part number for you.

  4. Dan remarks on April 30th, 2008 at 12:39 pm

    I think I found it…

    The part number I have used in the past is 64-2363. Not sure about the picture on their webpage, because it doesn’t really look like the stuff I have. It isn’t a hook and loop like Velcro. Both sides are the same, kind of like a ball on a stick. All the pieces put the same amount of force around each ball to hold it together.

    LINK

  5. Paul remarks on April 30th, 2008 at 3:09 pm

    You could also add another servo, mounted 90 degrees to the side, then linked into the other HP threaded hole to give you more lateral play. So one servo is up/down while the other is left/right.

    Assuming you have room for one more!

  6. Chris remarks on April 30th, 2008 at 3:56 pm

    I definitely have room and will be adding more servos to the dome. Side to side movement is not that great as the front holo housing is oval and restrictive. But I may still add an extra servo, especially if I drive it with some code rather than manually thru stick.

  7. Chris remarks on April 30th, 2008 at 4:12 pm

    Thanks Dan.

  8. Dan remarks on May 1st, 2008 at 4:49 am

    BTW, they are a 3M product. You may want to go to the store and look at them.

    I found another website about them which gives a closeup of what they look like.

    http://www.andybaird.com/travels/gertie/superlock.htm

  9. ShackMan remarks on May 1st, 2008 at 10:33 am

    Great work, as usualy, Chris. You make more progress on your upgrades/improvements than I’ll EVER make on my main assembly! 😉 ATM

  10. Chris remarks on May 1st, 2008 at 1:09 pm

    dan – i did pick some up last night, but man is it expensive for how much you get. i’m gonna try it out and then maybe shop around for a better price. 😀

    ATM – it helped that i took a week off to get ready for maker faire 😀

  11. Dan remarks on May 1st, 2008 at 1:26 pm

    I sent you an email about the stuff. See if it works for you. I am looking at getting a roll of the stuff at some point. It is cheaper by the yard. At 25 yards it is 50% off. I was thinking about trying the 250ct attached to the 400ct, the strongest bond. It might work for doors, maybe. it has a .23″ thickness when put together.

  12. Chris remarks on May 1st, 2008 at 6:36 pm

    i also found the same thing at Target today. The tape had 3M on it, but it was in Scotch brand packaging. Price was roughly $2.50 for a 4 x 3inch strips.

  13. Paul Novak remarks on May 13th, 2008 at 6:06 am

    Hi Chris,
    I have a general question about the servo setup. Does power only go to the servo when it is activated, or is there always power provided and it moves when a signal is sent? I was planning to build 12V in my dome through the slip ring and power everything from a busbar or fuse block, and want to make sure that plan is accurate.

    Thanks!
    Paul.

  14. Chris remarks on May 13th, 2008 at 1:31 pm

    my basic understand of servos is that power is always on, but the control signal triggers the electronics in the servo to turn the motor. sometime you’ll hear servos hum when they should be “off” because they’re active and not quite centered.

    did you see my servo boards where i dont route all the wires (power) to the dome, i just rebuild the 5v in the dome and send it onto the servos.

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