Working with Arduino:
Lesson #3: Force Sensitive Resistors
EGN1007
Learning Goals
Learning Goals: The student will be able to:
1. Build a complete circuit using the Arduino microprocessor
2. Identify important electrical components in a circuit and explain their
use
3. Identify and apply specific elements in “C” code used to run a
program in conjunction with how a circuit is built
Force Sensitive resistors
An FSR is identical to a potentiometer, except rather that varying its
resistance relative to shaft position its resistance varies with pressure.
A force sensing resistor is made up of two parts. The first is a resistive
material applied to a film. The second is a set of digitating contacts
applied to another film. The figure shows this configuration. The resistive
material serves to make an electrical path between the two sets of
conductors on the other film. When a force is applied to this sensor, a
better connection is made between the contacts, hence the conductivity
is increased.
The schematic symbol is that of a
regular resistor with an arrow through
it. And “f” net to the arrow is indicative
of FORCE.
Let’s Begin
1. Place FSR on G5 & G6
2. Run a red wire from the 5V on the
Arduino to H5. This will supply the
FSR with 5V.
3. Run a wire from Analog 2 to H6.
4. Place a 10KW resistor(Br-BL-O) in
I6 and I12.
5. Place the LED on G15 and G16
with the longer lead(+) of the LED
in G15.
6. Place a 560W resistor on H16 and
H22. Notice that both the resistor
and LED share row 16
7. Run a red wire from Digital 9 port
on Arduino to H15.
8. Run a black wire from H22 to the
ground(GND).
9. Run a black wire from H12 to I22.
Programming our sketch
Let’s define 2 variables as integers.
These will tell us which ports our
LED and FSR are in.
Programming our sketch
Just like before we need to set our LED as an output.
We have a new piece of code here: Serial.begin ( )
Sets the data rate in bits per second (baud) for serial data transmission. So
basically we are going to transfer 9600 bits per second to the computer. Old
modems attached to our phone lines used to work at this speed. This was
considered FAST back in the day, until 14400 finally came out.
Programming our sketch
We begin by creating a variable
called “value” which will read the
value on the FSR and divide it by 4.
This will then be written to the LED
and ALSO sent as a piece of data and
displayed in a Debugger Window.
When “println” is used after the Serial command it takes the reading
from the FSR and displays it in a window(debugger) for inspection.
Compile, download, and test. Does the LED light up.
Your turn!
Using what you have learned in this lesson
AND the last lesson, write a short program
that is BETTER than the one we wrote. Hint:
Use the debugger to get the values you need
and use information previously learned. The
response from the LED should be a bit
smoother.
Write your code on the lesson worksheet and
explain your code.
Challenge
Can you write a program that lights more than
one LED using the FSR so that they light in a
sequence or other pattern?
Write your code on the lesson worksheet and
explain your code.