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Topic: Servo Motors (Read 1 time) previous topic - next topic

jag3498

May 28, 2011, 06:31 pm Last Edit: May 28, 2011, 06:33 pm by jag3498 Reason: 1
Hi, I am very new to electronics and was wondering if servo motors such as this one http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/servo/List/0/SortField/4/ProductID/102/Default.aspx would work with Arduino without a motor shield. If they would work, I would like to buy 3 to make an autonomous robot. Also, how would I connect them and are there any possible locations that sell them, because shipping from that store is really expensive and I'm on a tight budget.

Thanks,
Jack

zoomkat

Servos can be used with the arduino (but need a seperate powersupply). Search the forum for servo to see hundreds of previous post to get up to speed on how they work.l with the arduino. Inexpensive servos can be ordered from sites like below.

http://www.hobbypartz.com/kahaoubrmo14.html

http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=9549
Google forum search: Use Google Advanced Search and use Http://forum.arduino.cc/index in the "site or domain:" box.

Terry King

Hi, Also look at:

http://xn--hgi.ws/YD-servos

These are already set up to run "Continuous Rotation" for Robot drive wheels.  Check shipping prices for where you are...


DISCLAIMER: I mentioned stuff from my own Shop...
Regards, Terry King  ..On the Red Sea at KAUST.edu.sa
terry@yourduino.com  LEARN! DO! (Arduino Boards, Sensors, Parts @ http://yourduino.com

jag3498

What is the differences between a continuous rotation servos and other servos?

Thank,
Jack

zoomkat

Quote
What is the differences between a continuous rotation servos and other servos?


http://www.google.com/search?q=continous+rotation+servo&hl=en&num=100&lr=&ft=i&cr=&safe=images&tbs=
Google forum search: Use Google Advanced Search and use Http://forum.arduino.cc/index in the "site or domain:" box.

AWOL

Quote
What is the differences between a continuous rotation servos and other servos?

One is a servo and one...isn't.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

jag3498

OK. I'm still confused. Would a regular servo work as a motor for a robot or would I need a continues rotation servo?

Thanks,
Jack

AWOL

It depends what you want the motor to do, and what compromises you're willing to make.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

jag3498

I want two motors to run two front wheel, being able to run at different speeds to allow turning, and be able to go backwards. And a third motor to turn a sensor or something.
Jack 

jag3498

Wait. So can continuous rotation servos keep turning and turning and turning, but regular servos can only turn 360 and then stop?

AWOL

Quote
but regular servos can only turn 360

Servos rarely manage 360 degrees.
180 or less is more normal.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

jag3498

But continues rotation servos can keep turning and turning? Also, how fast can they turn?

AWOL

Quote
But continues rotation servos can keep turning and turning?

They're not servos, because they have lost their feedback mechanism.
The fastest they can turn is the rating in their specification,  usually specified in degrees per second.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

jag3498

I think I am going to purchase this motor: http://www.sparkfun.com/products/9347. If I use two of these:http://www.sparkfun.com/products/341 to power it how could I keep the voltage at 6 volts?

cr0sh


I think I am going to purchase this motor: http://www.sparkfun.com/products/9347. If I use two of these:http://www.sparkfun.com/products/341 to power it how could I keep the voltage at 6 volts?


You're putting the cart before the horse.

For one thing, do you even know how much current one of those servos needs (running vs. stalled, as well), vs the mAh of the battery? If you don't understand this question, you'll probably end up with a robot that moves for about 5 minutes, then needs recharging.

In order to get 6 volts from a pair of those batteries, you would need some kind of voltage regulation scheme. In a pinch, a 7806 voltage regulator will do this, but you don't get much in the way of current output (about 1 amp - with a good heatsink); the 78xx family of regulators also aren't very efficient (and with such low battery mAh, you need as much efficiency as possible to extend your runtime). So now you're looking at a low voltage switching regulator (I know they make a 7805 equivalent form of these - so maybe a 7806 equiv also exists) - or building a buck converter, or something else.

Also - do you have a charger for those batteries - you can't just plug one of those up to anything to charge it (not unless you want a nice fire).

You'd be better off powering the servos from an 4-cell AA battery pack, running alkalines (for 6 volts) or NiMH (for 4.8 volts - or, if you can set up a 5-cell pack, you'll get 6 volts). This will give you the voltage you need, plus a greater mAh rating for longer run-time. You won't have to deal with voltage regulators, either. Run the Arduino off another pack separately...
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

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