We show how to build a pan and tilt for your camera using stepper motors and an Arduino.

Servomotor vs. Stepper Motor in a Servo Mechanism

Servomotor:

A servo is a device that uses a motor with few poles (4-12+) along with some kind of feedback to move a shaft to a particular position.
In the case of the servos we're accustomed to using, a simple potentiometer connected to the gearing allows us to put a servo in a particular position.

Stepper Motor:

A stepper motor is built on a multi-phase motor, with a large number of poles, (50-100+) that moves in "steps"
These steps are made by pulsing the various phases of the motor to achieve rotation
Stepper motors are usually NOT used with feedback, instead counting on their inherent angular position (created by the way the coils and magnets are laid out in the can) to "step" to particular positions.

Pro/Cons:

Stepper motors offer more torque at low speeds AND offer "holding torque" because of its inherent angular position.
Stepper motors tend to be cheaper
Stepper motors can be used without a position encoder
Stepper motors lose as much as 80% of their initial torque at 90% speed
Stepper motors are slow and not good at accelerating an opject
Because they have no positional feedback, it's possible to miss a step
Stepper motors suffer from vibration and resonance problems (annoying whine)

Now... let's take a look at OUR Stepper Motor!

28BYJ-48 Motor + ULN2003 Driver

Important Specs:

What does this tell us?

This will work on the same 5V power source we're using for the Arduino
A "stride angle" of 5.625 gives us 64 steps for a full rotation of the shaft. (360 / 5.625 = 64)
It is down-geared 64 times: That means the motor shaft has to spin 64 times for every time the stepper shaft rotates once.
This means we have 4096 steps for full rotation of the stepper shaft: (360 degrees / (5.625 / 64) = 4096)

OK... let's build!

Parts List:

Arduino of your Choice

Stepper Motor and Driver

5V Power Supply

Breadboard

What's What?

Let's put it together!

That's It!

Let's Program!

These show notes have been truncated due to length. For the full show notes, visit https://twit.tv/shows/know-how/episodes/209

Hosts: Fr. Robert Ballecer, SJ and Bryan Burnett

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