Download California University of Pennsylvania Department of Applied

California University of Pennsylvania
Department of Applied Engineering & Technology
Electrical / Computer Engineering Technology
EET 215: Introduction to Instrumentations
Lab No.11
Opto-Interrupter
(IR Emitter and Photo Transistor Pair)
Names:
1. Stephen Gilliland
2. Brandon Basista
3.
Signature:
Date
Box Sorting System
The main objective of this experiment is to understand the operation of a basic Opto-interrupter and
pule measurements using LabVIEW
Learning Outcomes
Students will demonstrate:
-
The ability to design, construct, and troubleshot a basic infra-red emitter detector
Ability to interface to a data acquisition system and perform measurements.
Introduction
Infra-Red emitter detector pair is used to sense whenever an object is blocking the light beam.
In this experiment, we will assume that different size boxes are traveling on a conveyer belt. The belt is
moving at a constant speed. The longer the light is blocked, the longer the resulting pulse width
becomes.
For our purposes, we will simply place a sheet of paper between the emitter and detector for a few
seconds. (between a fraction of a second and about 20 seconds.)
- Basic information needed:
1- the experiment is set up so that any duration less than 0.5 seconds results with an indication of a type
0 box.
2- The duration that a box blocks the beam is rounded to the nearest integer.
3- The goal is to experiment with opto-interrupters, however, the sorting process is used to bring more
fun into the experiment.
Opto-Interrupter
A- Refer to this link
http://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/H22A1,2,3.pdf
Questions:
1On the Emitter side (diode): What is the absolute maximum continuous forward current ?
60mA
2On the Detector side (Output transistor), what is the maximum power dissipation?
150mW
3For the H22A1 interrupter, what is the forward current IF for the ON state 5mA and the
Saturation State 30mA (found in the table)
4Draw the equivalent circuit as seen under “Package Outline “ and label pin numbers according
to the figure shown on page -1 of the datasheet.
B- Circuit Design
Refer to the figure below to determine resistor values.
- IR Emitter side (Diode):
Calculate RD for IF = 25mA. Assume VD = 1.7 Volts and the supply is 5V
RD = 132Ω
- Photo-detector side (photo-transistor):
Calculate RC so that VCE = 0.2V and IC= 4.8mA
RC = 1000Ω
Components Needed:
-
Opto-interrupter
-
1KΩ resistor (Use for RC)
-
330 Ω or 220 Ω resistor (use for RD)
-
Paper
Experiment
A- Build the circuit shown above with the values given in the list of components
1- launch the ELVIS instrument launcher and monitor the Source Analog input 0 (AI0) on channel 0.
Set the vertical scale to 1V/Div. Make sure that the Enable check box is checked.
2- Run the scope and monitor the signal swing high and low as you place and remove the paper between
the emitter and detector.
3- Does this part work fine? Yes, it does. If NOT, must fix the problem before proceeding. Otherwise
the experiment will not work.
Questions:
Why does the output swing to High when the paper is placed in the slot to block the IR light ?
The emitter acts as the base for the transistor on the detector side of the Optical Switch, when the
optical connection is interrupted the transistor is no longer in saturation and a voltage appears across
VCE
Why does the output swing to low when the IR beam is not blocked?
Because there is a base voltage which saturates the transistor. This causes a 0.2V drop across VCE.
----------------------------------------------- ---------------------------------B- Once Part –A works fine, the circuit is ready for the LabVIEW interface.
1Turn Off the scope of the instrument launcher (so that no data acquisition channel or device
conflict occur.)
2-
Turn off the ELVIS board.
3-
Download the VI for this lab from the course’s page (Lab11 VI)
4As was done with previous experiments, set up the DAQ to acquire voltage at analog input 0
(AI0) using the following settings: Of course, you may need to delete the DAQ and added again.
5- Reconnect the DAQ to the rest of the items in the block diagram.
6-
Turn the board’s power ON.
7here.
Run the VI (note, do not click on the continuous run icon, just click on the Run arrow as shown
8- study the performance as you place a sheet of paper in the slot of the opto-interrupter for different
time durations.
9- Comment on your observations.
When the optical connection was blocked a high signal of 5V was displayed. This remains high as long as
there was something interfering with the optical connection.
Final note,
in a sorting system, servomotors or stepper motors may then be activated to move boxes of different
sizes to proper bins.
Instructor approval of experiment completion: CHECK