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Ideas for powering Servos and stepper, from 11.5v battery? — Parallax Forums

Ideas for powering Servos and stepper, from 11.5v battery?

rwgast_logicdesignrwgast_logicdesign Posts: 1,464
edited 2013-12-28 00:50 in General Discussion
I have not posted much lately, not have I updated the thread on my string ray for those of you who may have been following it. I have just been fairly busy, and using any spare time to actually work on the Robot, I plan to do a huge update when I have more done. Anyways I am running two 8 cell NiMH packs, one for the motors and one for all the logic. Both battery packs are controlled by relays. Im just about done with all the bottom level guts of the stingray and realized I never accounted for powering my 5v stepper motors and servos, just the logic and the main motors!!

Servos and steppers can draw quite a bit of current when holding, so im wondering if anyone has a thought on how I can power them? The only thing I can really think to do at this point is to set up a 5v power rail running off a switching regulator that can handle 3 to 5 amps or so..... I dont really like this idea though... Is there maybe a way I could use a transistor and a voltage reference, or something a bit more simple I may be over looking?

2013-12-27 17.18.04.jpg
2013-12-27 17.18.04.jpg
1024 x 577 - 100K

Comments

  • kwinnkwinn Posts: 8,697
    edited 2013-12-27 19:57
    It can be done with a simple 3 terminal regulator, a power transistor, and heat sink hefty enough to handle the current/power requirements but that is very inefficient and makes for a short run time. That is why switching circuitry is used for this.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2013-12-27 20:30
    It sure seems like a switching regulator is simple enough as long as you don't have to build it yourself. That's what ebay is for. These should be good for a couple of amps. Erco posted links to beefier regulators a while back. I'll add a link if I can find his post.
  • ercoerco Posts: 20,256
    edited 2013-12-27 21:22
    Keep up with price drops, Duane. Those buck regulators cost just that now: http://forums.parallax.com/showthread.php/146544-DC-DC-Step-Down-Converter?p=1230541&viewfull=1#post1230541
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2013-12-28 00:50
    Wow thanks erco & Duane. I had no idea these were so cheap on ebay, I feel like ive wasted a lot of time slapping together switchers. Those prebuilt regulator packages are cheaper than buying the switcher ic they use!
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