12.3: shift register lab and introduction to motors

 

This week's lab is on shift registers, which allow us to expand the number of output pins we can use. The arduino has a limited amount, but by using a shift register and software, we can create more on a breadboard. These are the instructions we used: https://lastminuteengineers.com/74hc595-shift-register-arduino-tutorial/

A shift register is an integrated circuit package (IC), specifically, a dual inline package (DIP). It's like a train of binary that sends on or off signals to the pins in the line. Serial data is being input, and parallel data is being output. 

In software, "clocking" feeds data into one line of pins, and "latching" pushes the data over to the pins that control our desired outputs.  

Using an i loop to gradually push data to pins in a pattern that causes a desired output is an important aspect of the shift registers: in the two examples below, an i loop is what causes the pins to get turned on one by one.

the bitSet(); call causes the leds to turn on and stay on.

Motors

Motors are the principal way things could get moved around in our next project. Other ways might be something like pneumatics (airflows).

Types of motors

DC motor:

    draws a lot of power

DC gearhead motor

    slower, more powerful

    might use mechanisms like pulleys or belts for more complex motion (like reciprocal linear, which is going back and forth)

Intermittent rotary, such the geneva wheel:

    rotates a certain fraction of a full rotation at a time, with pauses between. 

Stepper Motor

   usually really powerful

   moves a specific distance

   harder to control and needs a driver

   4+ wires

Servo Motor

    moves to a specific position

    consumes lots of current

AC synchronous motor

    can be plugged into a wall

    very slow and easy to find, but not compatible with our arduinos because they run on DC.

Gears allow us to control the power and speed of motors, which have an inverse relationship. Oftentimes motors are much too fast and not powerful enough. Mechanical advantage allows us to use things like gears to shift the motor's potential from speed to power. 

A driving gear is attached to a motor; that gear interlocks with another gear: the driven gear. Power of the driving motor and relational quantities of gear teeth cause changes in speed and outputted power.

For example, a driven gear with half the teeth of the driving gear will double the speed:

Gears might also be stacked like this in a gearbox to slow the motor down and increase its power significantly.