Download Lab8A- Ping

California University of Pennsylvania
Department of Applied Engineering & Technology
Electrical / Computer Engineering Technology
EET 215: Introduction to Instrumentations
Lab No.8-( Part 1 of 2)
Distance Measurements Using Ultrasonic Sensors.
Names:
1.
2.
3.
Signature:
Date
Instrumentation Amplifier
Objective of the Experiment
The main objective of this experiment is to understand the operation of a basic ultrasonic sensor and
the triggering circuitry.
Learning Outcomes
Students will demonstrate:
-
The ability to design, construct, and troubleshot astable and a monostable multivibrators.
Ability to relate the timing diagram to the basic understanding of the two multivibrators
The ability to develop a linear relationship between pulse width and distance measurements
The ability to interface to to a DAQ system to display distance measurements.
Introduction
This experiment I divided into two parts:
Part -1 (Today’s experiment) is astable multivibrator circuit
Part-2 (next week’s experiment) is the triggering circuit and the ultrasonic transmitter/receiver
interface.
Triggering Circuit.
This circuit is composed of two stages. The astable (free running) multivibrators. This part provides a
clock timing to the monostable (one-shot) circuit.
A-
Astable (Free Running ) multivibrator
Source:
http://www.electronics-tutorials.ws/waveforms/555_oscillator.html
This circuit provides an output according to the following equations:
t1 = high time = 0.693(R1+R2)C1
t2 = low time = 0.694 R2C1
T = period = t1+t2
f= 1/T
B-
Monostable (One-Shot) multivibrator
This circuit provides a single pulse once a negative edge trigger is applied to the input(pin-2). The
duration of the pulse is determined by the components R1 and C1 as follows:
tON = 1.1 R1C1
The negative edge trigger is a result of the signal from the free-running multivibrators and a wave
shaping circuit (to be shown later.)
Components Needed:
-
555 timer
-
200KΩ resistor
-
47KΩ resistor
-
0.1uF cap
Experiment
Close LABVIEW and turn the power to the board off
For better connections and less errors. Connect one of the busses on your breadboard to 5V and the
other to GND.
A-
Build the free-running multivibrator circuit shown:
VCC
5V
R1
200kΩ
8
VCC
R2
47kΩ
4
RST
7
DIS
6
THR
2
TRI
5
CON
OUT
GND
1
C1
0.1µF
3
BCalculate the anticipated high and low times as follows:
t1 = high time = 0.693(R1+R2)C1
t2 = low time = 0.694 R2C1
T = period = t1+t2
f= 1/T
thigh
(ms)
tLow
(ms)
T
(ms)
f
(Hz)
CTurn the breadboard power on and monitor the Timer’s output on Ch0 (use the BNC connector)
DLaunch the ELVIS instrument launcher and on the score of Ch0, monitor the output. (The output
is on pin 3 of the timer.) You should see a waveform similar to the one below. Ensure that the settings
on the scope are correct. (may refer to previous labs if needed.)
E-
From the Scope, record the high and low times
thigh (measured)
(ms)
tLow (measured)
(ms)
F- Are the measured and calculated values close ? -----------------------
G-
Monostable Multivibrator (One-Shot) and interface circuit (Next Week.)
Instructor approval of experiment completion: