Day 9: (Wed Sep 29, Week 5) Photointerrupter in Action

Notes for 2021-09-29.

New Assignments

1. New assignment, due next class: Exercise: Reactive Marble Run Tile.

Agenda

1. Summary electrical theory review.

2. Introduce new assignment.

3. Demo of reading a switch with a Pico.

   • 3.3V vs 5V circuits

4. Oscilloscope demo.

5. Sample code walkthrough: digitalio, logic levels, state machines, hysteresis.

6. Sample CAD walkthrough.

7. Sensor lead extension and heatshrink demo.

8. Hand out a few more parts from the F21 Course Kit (1931, 6049, 482).

9. In-class sketching, prototyping, and individual design review.

Supplementary Video

• Electrical Theory Introduction: https://youtu.be/d5HxmQHCO48

• Kirchhoff’s Laws, Ohm’s Law: https://youtu.be/hnbD_D4ljOE

• Resistors and Voltage Dividers: https://youtu.be/j8rvBSPiiUI

• Switch and LED Circuits: https://youtu.be/lY3ckgUBEbg

• Reflective Photointerruptor: https://youtu.be/atuFgbVYVsA

• Resistive Circuits in Tinkercad: https://www.youtube.com/watch?v=mX5L67WcWec

Photointerrupter Circuit

A photointerrupter circuit includes a current-limiting resistor for the LED and a bias resistor for the phototransistor.

Raspberry Pi Pico diagram of pin functions.

Essential Lab Equipment

Solderless breadboards are our workhorse for electronics prototyping. Each short row of five holes connects together by an internal metal clip and forms a single circuit node. Each long bus row is a node. Please disregard the +/- bus labels on your breadboards.

Three-channel lab power supplies.

Digital multi-meter (DMM).

Digital oscilloscope. For more details, please see Oscilloscope Guide.