When this pushbutton is pressed, it is in its active state. If you think of GND as a “low” voltage, and 3.3 V as a “high” voltage, a pushbutton that sends a 3.3 V high signal when you press it is considered active high. When a pushbutton is not pressed it is in a 0 V, low resting state.
In these activities, you will write scripts to control the servo motor directly. In addition, you will also incorporate the pushbutton circuits from earlier activities for servo control and the LED circuits as indicators.
The focus of this chapter was calibrating and testing the servos, and building indicator lights to monitor the servo signals. In addition to some hardware setup, many concepts related to electronics, programming, and even a few good engineering concepts were introduced along the way.
Hardware Setup
Electronics
Let’s test Kirchhoff’s current law by verifying the current into a node is equal to the sum flowing out. We can do this by connecting another green LED circuit to the ammeter.
Both LED circuits will conduct about 5 mA. If both of them are connected to ground through the ammeter, the sum of the currents flowing through the 20 Ω resistor should be about 10 mA.
In this activity, you will connect the LED circuit to a micro:bit I/O pin and use a script to turn the light on and off. You will also use the script to adjust the on/off rate and number of times it blinks. Last, but not least, you will calculate the timing of the lights. The three most common ways to quantify timing are called period, frequency, and duty cycle.
Imagine that your cyber:bot is navigating a course, and there’s a dark or shady area at the end, such as a cardboard box garage. Your robot’s final task in the course is to stop inside that dark area. Or, perhaps you want the robot to search for and stop under bright light. There’s a simple phototransistor circuit you can use that lets the micro:bit module know it detected bright or dim light by comparing the ambient light to some specified level.
Imagine that your BOE Shield-Bot is navigating a course, and there’s a bright light at the end. Your robot’s final task in the course is to stop underneath that bright light. There’s a simple phototransistor circuit you can use that lets the Arduino know it detected bright light with a binary‑1, or ambient light with a binary-0. Incandescent bulbs in desk lamps and flashlights make the best bright-light sources. Compact fluorescent and LED light sources are not as easy for the circuit in this activity to recognize.
Build a smart robot with this step-by-step tutorial for using the Robotics Shield Kit from Parallax and your own Ardunio Uno, Duemilanove, or Mega.
Teaching robotics in a school or club? Check out each Chapter Summary to see what STEM skills and concepts your students will soak up.
In this tutorial's activities, the pushbuttons you add will be used to control the lights from LED Lights. You will also use the alligator clip probes to test continuity between pushbutton terminals and voltages at key points in pushbutton circuits.
