SparkFun Forums

[warcormc]

Sorry if this has already been answered. I guess I need a motor primer. Basically I need to program an arduino with ardumoto shield to move a two pieces of balsa wood. extremely light (like only a few ounces). Precision isn't that much of an issue. What motors/servos should I buy?

-mike

[esklar81]

mike,

You'll need to provide a bit more information for us to be able to help, such as:

1. dimensions of the pieces of wood
2. whether motion is linear or rotational
3. distance or angle to be moved
4. speed at which the pieces are to be moved
5. available electrical power
6. desirable precision and reproducibility (distance or angle)
7. whether open loop or closed loop control is desired

Eric

[warcormc]

right I was a bit vague. Basically the wood I'll be moving is actually a wooden gear moving a piece of balsa wood attached to another piece.

so for the first motor let's say
diameter of 3 or 4 inches.
rotational motion
complete rotation
no preference on speed.
available power is whatever is on board the arduino. (can't be more than 6V or so)
precision isn't too important so within 15 degrees or so.
open loop.

sorry if that too is vague.

[esklar81]

mike,

Is "complete rotation" a 360 degree swing, or do you mean continuous rotation (ability to turn an arbitrary number of rotations in one direction without any in the opposite direction)?

For a single 360 degree range and low power, a servo may be your best bet, as you get to send a position, rather than a speed.

For multiple rotations, I suggest you consider a stepper motor or use closed loop control (such as incorporating an encoder or detecting the endpoints of the intended motion). Using a conventional motor and open loop control of speed and duration is likely to get you increasing error with time. Error will also depend on consistency of the mechanical load on the motor and of the power supply.

Lastly, I discourage using power from the Arduino for moving anything. That way lie a host of electrical noise and voltage sag problems. Feeding the Arduino and the motor from a common power source is probably a better move. If you're using a 5 V Arduino, you should feed it at least 7 V.

Eric