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Got 84 Servos? — Parallax Forums

Got 84 Servos?

ercoerco Posts: 20,259
edited 2011-11-21 10:43 in General Discussion
http://www.robot-electronics.co.uk/acatalog/Servo_s_and_Controllers.html ordering info
http://www.robot-electronics.co.uk/htm/sd84tech.htm tech specs

84-servo centipede robots, unite! OK, many can be used as digital or analog inputs too.

Comments

  • Ken GraceyKen Gracey Posts: 7,401
    edited 2011-11-08 23:57
    erco, maybe you can build this centipede. With 84 servos I'm wondering if the bot will be able to carry it's own power supply.
  • ercoerco Posts: 20,259
    edited 2011-11-08 23:58
    You're up late, trolling the forums, Boss! Get some sleep!

    Actually, I probably have over 60 of those cheapie 9g servos from Ebay China. At $1 each, how could I say no...
  • Ken GraceyKen Gracey Posts: 7,401
    edited 2011-11-09 00:00
    OK. I'm outta here for the night. I'll think about robots tonight. Better than that thread about Chinese manufacturing. . . that'll keep me up!
  • pedwardpedward Posts: 1,642
    edited 2011-11-12 16:10
    Heck, you can drive 32 servos per Propeller, why do you need that board?
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-11-12 16:43
    With Jazzed's TetraProp board you could control 120 servos and still have two pins on each Prop for communication with the outside world and to use for communication amoungst themselves.

    I added up how much it cost me to build one of Jazzed's boards. The grand total was $63. Not too bad to control 120 servos.

    Duane
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2011-11-13 00:00
    pedward,

    "Heck, you can drive 32 servos per Propeller, why do you need that board? " - actually you can drive about 144 Servos from one Propeller (and a few additional IC's) before your pin limited.

    A single COG can drive 48 servo's ... using 1 COG you can drive 144 Servos... There is a link I will find later that shows how this can be done with only One Propeller. The caveat is managing the power requirement. As long as you have an understanding of the power requirement for all of your servo's then this method will work fine.

    Reference to 144 Servo driver..
    http://forums.parallax.com/showthread.php?84187-Will-the-servos-Parallax-sells-work-from-a-pulse-directly-from-the-Propeller&p=583652&viewfull=1#post583652
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-11-13 15:53
    I haven't use a 74xxx573 IC before.

    I'm going to make sure and get a bunch with my next Digi-Key order.

    Oh, I'm also going to need some servos. And something for the servos to control.

    Maybe I'll use erco's centipede idea. I've also always wanted to make a snake with a bunch of servos.
  • ercoerco Posts: 20,259
    edited 2011-11-13 16:34
    I always get my techno butt kicked when all you SCHMART guys dogpile on. :)

    OK Duane, let's see your centipede, Pal!
  • pedwardpedward Posts: 1,642
    edited 2011-11-14 00:10
    I would throw out that the 74LS373 is possible easier to come by and is the same functional part. Also, if you used a 74138 3 to 8 line decoder, you could trim 3 lines, get automatic BCD translation in the multiplexing and add 2 zones to the same setup, using 11 lines to drive 64 servos. Furthermore, you could simply swap in a 4-16 line decoder and do 128 servos with 12 pins.

    I'm shooting from the hip, but if you decoupled the inputs of each servo with a small cap (just guessing .1uf or .01uf), you could probably get away with the smaller effective duty cycle, but higher multiplex rate to smooth out the latched outputs.
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2011-11-14 08:25
    pedward,

    Yes, the 373 is functionally equivalent to the 573, however the pin-out is different between the two. The 573 was chosen to optimize layout.
  • pedwardpedward Posts: 1,642
    edited 2011-11-14 09:56
    Beau Schwabe (Parallax) wrote: »

    The 573 was chosen to optimize layout.

    Sounds like someone has spent too much time routing ICs! :)

    I was just suggesting it because it's an older part number that could be easier to come by for hobby crowd, like in the junk drawer.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-11-14 14:46
    erco wrote: »
    OK Duane, let's see your centipede, Pal!

    erco, please don't use your Super Hypnotic Powers to make me build a robotic centipede. Your SHPs have already make me buy a bunch of robots and supplies. There's the Roboni-I(two of them), a Roomba, a bunch of purple NiMH batteries from China, all purchased after learning of their existance from one of your posts. I'm pretty sure there are more but your SHPs have made me forget them.

    Have mercy and let me finish some of the other projects you've ordered me to do before making me construct a robotic centipede.

    I'm still trying to obey your orders to match your odometery experiments. (I have hand-made many encoder disks as ordered.)

    Did you see the relay cell phone dialer I made? You are pleased to see your order to use relays in projects carried out, no?

    My comment:
    Maybe I'll use erco's centipede idea.

    was in responce to your SHPs used in the OP. I hope to delay this activity a year or two.

    Take pitty on your devoted minion and don't lay this additional burden on me?!
  • ercoerco Posts: 20,259
    edited 2011-11-14 15:14
    OK, fine. Whatever you do, DON'T build a centipede. In fact, I FORBID IT!

    Great use of relays in your cell phone dialer, BTW! :)
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2011-11-14 17:33
    Duane,

    Don't build it... :-) ... actually I would love to see something like that :-)

    Just remember ...
    "Naturally evolved systems often solve problems we are incapable of even formulating." - centipede
    "Engineering is an advanced form of agreement with reality." - attempting to build a centipede
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-11-15 15:51
    pedward wrote: »
    Heck, you can drive 32 servos per Propeller, why do you need that board?

    I assume people buy boards like this because it has all the convenient electrical connections for attaching all those servos, the various power taps for splitting up the power requirements of that many servos, and someone else's effort in doing the coding, so I don't have to. Having done numerous multi-servo projects in the past (though, honestly, nothing with more than 28 servos), I can say the wiring alone is a PITA. I'm always looking for premade boards that simplify servo hookup.

    Some of us want a corned beef sandwich without first corning the beef!

    Is it that Gerry didn't use a Propeller on his board? Given that it would be cheaper to use just one Propeller in place of all those PICs he'd probably be willing to entertain the idea.

    -- Gordon
  • ercoerco Posts: 20,259
    edited 2011-11-21 10:43
    Or a Ssssssssssnake, perhapssssss... http://www.snakerobots.com/S5.html
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