Intro to Sensors
Class Information
Format: 2 weekday evening sessions, 2 hours each
Most Recently Taught: July 18 & 25, 2012
Instructors: Christalee Bieber & Daniel Bergey
Description: Sensors help us hear what the world around us has to say. In this class you will build circuits that measure temperature, light, and motion. We will cover voltage and current control, and use transistors and op-amps (amplifiers) to drive LEDs and lightbulbs. Our examples will all be analog, but the techniques are also useful for connecting sensors to microcontrollers.
Bring your own project ideas, or use ours to start. Each session will have time to work on your project with help from instructors. No electronics background is required. All ages welcome; students 13 and under should be accompanied by an adult.
Learning Objectives
Upon completing this course, students should be capable of:
- designing & analyzing circuits containing sensor elements
- finding key information on electronic components' datasheets
- using transistors and op-amps to control voltage and current in sensor circuits
- reading circuit schematics & resistor values
- building example circuits on breadboards
Class 1 Outline (PDF)
Class 1 Handout (PDF)
- Introductions, orientation (20 min.)
- backgrounds & interests
- brainstorm about sensor types, applications
- overview of Class 1, Class 2 topics
- orientation to handout
- Switches & resistors (20 min.)
- Activity: basic lightbulb circuit example
- Activity: add a switch
- Concept: introduce circuit notation, key symbols
- Concept: how does current flow in a network? what is voltage?
- Activity: add different-valued resistors, potentiometers
- Concept: V=IR, P=IV, series & parallel circuits
- Sensors are mostly switches or resistors (20 min.)
- switches: photodiode, knifethrow, push button, tilt switch, beam-break, reed switch
- resistors: thermistor, photoresistor, potentiometer, load cell
- (but some aren't): windspeed, rainfall, relative humidity, oxygen ppm
- Activity: pick a reed switch or push button to put in your circuit
- brief show & tell/knowledgeshare
- Note: Some students built circuits which light up when the switch closes, and some turn off.
- Hands-on with more circuits (50 min.)
- Activity: practice building sensors in Fig. 2, 3a
- Concept: transistor pinout & schematic
- Concept: matching resistor values to sensors
- Wrap-up (10 min.),
- Clean up, have students put their names on breadboards for next class
- What did we learn?
- What didn't work?
- Extra Topics (as time allows)
- revisit sensor types with an individual project focus
- LEDs & directional components
- practice circuit diagrams, math
Class 2 Outline (PDF)
Class 2 Handout (PDF)
- Introduction (15 min.)
- orientation to handout
- brief review of Class 1
- BJT Power Amp (30 min.)
- rules transistors follow in circuits
- VE = VB - 0.6V
- ICE = h * IBE (h ~ 100)
- Review: voltage follower circuit
- Activity: current source circuit
- Input Conditioning (10 min.)
- read the documentation for I-V curves
- Concept: think about the range of inputs you're going to get (e.g. temperature), and outputs you want (what are you driving?)
- Op-Amps (55 min.)
- how to insert DIP components into breadboards
- Concept: open-loop vs. closed-loop configuration
- Op-amp multiplies the difference between its inputs. But we never use them open-loop.
- Activity: tuning gain with resistors
- Activity: comparator to subtract constant voltage
- Concept: why build these complex circuits?
- Wrap-up (10 min.)
In addition to the handouts, datasheets for each major component were made available for students to consult during class.
Items Needed
Pedagogical Notes
Example circuits and transistor & op-amp concepts were developed with reference to the following text, particularly Chapters 2 and 4.
Horowitz, Paul, and Winfield Hill. The Art of Electronics. 2nd ed. Cambridge University Press, 1989. ISBN: 978-0521370950.
Source Files (ZIP)