Un altro utilizzo del NE555 Circuito di rilevamento degli ostacoli in

Un altro utilizzo del NE555
Circuito di rilevamento degli
ostacoli in un robot
Vediamo un altro utilizzo del NE555. vogliamo realizzare un robot in grado di seguire autonomamente
un percorso rilevando ostacoli sulla sua traettoria. Lo schema generale del sistema è il seguente
Un microcontrollore riceve informazioni da un sistema di rilevazione degli
ostacoli, ed in base ad esse modifica la traettoria seguita comandando le ruote
del robot.
Il circuito di rilevamento degli ostacoli è costituito da sensori PNA4602 della Panasonic che rilevano
radiazioni nel campo del infrarosso. Questo sensore ha una frequenza di lavoro di 38 KHz. Un led d
infrarossi deve emettere una radiazione ad infrarosso con questa frequenza, questa radiazione rimbalza
sull’ostacolo e raggiunge il sensore consentendo di rilevare l’ostacolo.
Di seguito abbiamo il circuito di pilotaggio del led. Un oscillatore basato su NE555 genera un’onda
quadra di frequenza opportuna che comanda un bjt il quale comanda l’accensioen e lo spegnimento
del
led
a
infrarossi
gereando
il
segnale
che
deve
rimbalzare
sull’ostacolo.
Il circuito è leggermente diverso da quello studiato come astabile, ma il funzionamento è identico. Con
il condensatore C1 inizialmente scarico l’uscita del NE555 si trova a livello alto poiché nel latch S=1 ed
R=0. il condensatore carica attraverso R1 che lo collega all’uscita Out fino a alla soglia di 2/3Vcc in
corrispondenza della quale l’uscita del NE55 commuta a zero facendo scaricare il condensatore e così
via.
Si avrà
T = t H + t L = 0.7(2 R1 )C = 1.4 R1C
1
f =
1.4 R1C
Scelto C da 1 nF, per ottenere una frequenza di 38 KHz dovremo avere
1
1
−6
R1 =
=
=
0
.
0188
*
10
= 18.8KΩ
3
−9
1.4 fC 1.4 * 38 *10 *10
Tale valore verrà ottenuto nel circuito mediante la resistenza fissa R1 ed il trimmer R2. la
resistenza R5 è una resistenza di pull up che serve per interfacciare un pulsante non
esplicitamente visibile nello schema che serve a portare il reste del NE555 a zero bloccando
così l’oscillatore.
Photo IC
PNA4601M Series
(PNA4601M/4602M/4608M/4610M)
Bipolar Integrated Circuit with Photodetection Function
For infrared remote control systems
Unit : mm
External parts not required
2.3
0.8
2.0±0.1
3-1.5±0.2
22.0 min.
Absolute Maximum Ratings (Ta = 25˚C)
Parameter
5˚
5˚
Adoption of visible light cutoff resin
Symbol
Ratings
VCC
– 0.5 to +7
V
Power dissipation
PD
200
mW
Operating ambient temperature
Topr
–20 to +75
˚C
Storage temperature
Tstg
– 40 to +100
˚C
Power supply voltage
R2.25±0.1
5˚
Extension distance is 8 m or more
2.25
5˚
8.0±0.2
5.2
Features
5.25±0.3
Not soldered 1.5
7.0±0.2
3.5
1.0±0.1
3-0.5 +0.2
–0.15
0.45±0.2
Unit
1
2
3
2-2.54
1: VOUT
2: GND
3: VCC
Main Characteristics (Ta = 25˚C VCC = 5V)
Parameter
Symbol
Conditions
min
typ
max
Operating supply voltage
VCC
Current consumption
ICC
Note 3
Maximum reception distance
Lmax
Note 1
8
Low-level output voltage
VOL
Note 2
4.7
5.0
5.3
V
1.8
2.4
3.0
mA
High-level output voltage
VOH
Note 3
Low-level pulse width
TWL
Note 1
High-level pulse width
TWH
Note 1
200
PNA4602M
PNA4608M
m
0.35
0.5
4.8
5.0
VCC
V
200
400
600
µs
400
600
µs
PNA4601M
Carrier frequency
10
Unit
V
36.7
38.0
f0
56.9
PNA4610M
kHz
33.3
Note 1) Fig. 1 burst wave, L = Lmax, 16 pulses
Note 2) Fig. 2 continuous wave, L ≤ Lmax
Note 3) Light shut off condition
Carrier wave : f0
400µs
Carrier wave : f0
400µs
Fig.1
Fig.2
1
PNA4601M, PNA4602M, PNA4608M, PNA4610M
Photo IC
Block Diagram
VCC
(20kΩ)
AGC
B.P.F
demodulator
PD
comparator
integrator
peak hold
,,
,,,
constant voltage
RL
VO
,,
amplifier
GND
Panasonic Transmitter Specifications
LED Transmission unit
Standard reception unit
10kΩ
10V
PNZ323B
10µF
20cm
V out
10kΩ
V out 55mV
10kΩ
GND
The light output of the LED transmission unit is adjusted so that the transmission output (V out) of the standard
reception unit will be 55 mV when the transmission waveform (duty = 50%) is output from the LED transmission unit. Here, infrared sensitivity (SIR) of PNZ323B is 0.53 µA when emission illuminance (H) is 12.45 µW/
cm2.
The maximum reception distance under these specifications is an assurance that TWH and TWL values will be
within the tolerance ranges when 16 consecutive pulses of an optical output equivalent to the maximum reception distance are transmitted by the above transmission unit (The maximum reception distance is measured in
the dark without external disturbance noise.)
2
PNA4601M, PNA4602M, PNA4608M, PNA4610M
L max — Ta
100
Relative sensitivity S (%)
100
80
60
40
80
60
40
20
20
0
– 20
VCC = 5V
Transmitter : Standard LED
Transmission unit used
0
20
40
Ambient temperature
60
80
100
Ta (˚C )
Spectral sensitivity characteristics
100
80
60
40
20
0
33
35
37
39
41
43
Carrier frequency (kHz)
* The peaks for PNA4601M, PNA4608M,
and PNA4610M are all f0.
0
600
700
800
900
Wavelength
1000 1100 1200
λ (nm)
Directivity characteristics
0˚
10˚
20˚
100
90
80
70
60
50
40
30
20
Relative reception distance (%)
Relative reception distance L max (%)
120
B.P.F frequency characteristics
(PNA4602M)*
Relative sensitivity S (%)
Photo IC
30˚
40˚
50˚
60˚
70˚
80˚
90˚
3
PLASTIC INFRARED
LIGHT EMITTING DIODE
QED233
QED234
PACKAGE DIMENSIONS
0.195 (4.95)
REFERENCE
SURFACE
0.305 (7.75)
0.040 (1.02)
NOM
0.800 (20.3)
MIN
0.050 (1.25)
CATHODE
0.100 (2.54)
NOM
0.240 (6.10)
0.215 (5.45)
0.020 (0.51)
SQ. (2X)
SCHEMATIC
NOTES:
ANODE
1. Dimensions for all drawings are in inches (mm).
2. Tolerance of ± .010 (.25) on all non-nominal dimensions
unless otherwise specified.
CATHODE
DESCRIPTION
The QED233 / QED234 is a 940 nm GaAs / AlGaAs LED encapsulated in a clear untinted, plastic T-1 3/4 package.
FEATURES
• = 940 nm
• Chip material =GaAs with AlGaAs window
• Package type: T-1 3/4 (5mm lens diameter)
• Matched Photosensor: QSD122/123/124
• Medium Emission Angle, 40°
• High Output Power
• Package material and color: Clear, untinted, plastic
• Ideal for remote control applications
 2001 Fairchild Semiconductor Corporation
DS300338
10/31/01
1 OF 4
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PLASTIC INFRARED
LIGHT EMITTING DIODE
QED233
ABSOLUTE MAXIMUM RATINGS
QED234
(TA = 25°C unless otherwise specified)
Parameter
Operating Temperature
Symbol
Rating
Unit
TOPR
-40 to +100
°C
Storage Temperature
TSTG
-40 to +100
°C
Soldering Temperature (Iron)(2,3,4)
TSOL-I
240 for 5 sec
°C
Soldering Temperature (Flow)(2,3)
TSOL-F
260 for 10 sec
°C
IF
100
mA
Continuous Forward Current
Reverse Voltage
VR
5
V
Power Dissipation(1)
PD
200
mW
Peak Forward Current
IFP
1.5
A
1. Derate power dissipation linearly 2.67 mW/°C above 25°C.
2. RMA flux is recommended.
3. Methanol or isopropyl alcohols are recommended as cleaning agents.
4. Soldering iron 1/16” (1.6mm) minimum from housing.
5. Pulse conditions; tp = 100 µs, T = 10 ms.
ELECTRICAL / OPTICAL CHARACTERISTICS
PARAMETER
TEST CONDITIONS
DEVICE
Peak Emission Wavelength
IF = 20 mA
ALL
Spectral Bandwidth
IF = 20 mA
ALL
IF = 100 mA
ALL
Emission Angle
IF = 100 mA
ALL
Forward Voltage
IF = 100 mA, tp = 20 ms
ALL
IF = 100 mA
Reverse Current
VR = 5 V
Radiant Intensity
IF = 100 mA, tp = 20 ms
Temp. Coefficient of
PE
Temp. Coefficient of VF
(TA =25°C)
MIN
TYP
MAX
UNITS
—
940
—
nm
—
50
—
nm
TC
—
0.2
—
nm/K
—
40
—
Deg.
VF
—
—
1.6
V
ALL
TCV
—
-1.5
—
mV/K
ALL
IR
—
—
10
µA
10
—
50
27
—
—
QED233
SYMBOL
PE
2
1/2
IE
QED234
Temp. Coefficient of IE
Rise Time
Fall Time
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IF = 20 mA
IF = 100 mA
ALL
TCI
—
-0.6
—
ALL
tr
—
1000
—
ALL
tf
—
1000
—
2 OF 4
mW/sr
%/K
ns
10/31/01 DS300338
PLASTIC INFRARED
LIGHT EMITTING DIODE
QED233
QED234
TYPICAL PERFORMANCE CURVES TBD
Fig. 1 Normalized Radiant Intensity vs. Forward Current
Fig. 2 Forward Voltage Vs. Ambient Temperature
2.0
IF = 50mA
Normalized to:
IF = 100 mA
TA = 25˚C
tpw = 100 µs
1
VF - FORWARD VOLTAGE (V)
Ie - NORMALIZED RADIANT INTENSITY
10
0.1
0.01
1
10
100
1.5
IF =10mA
1.0
IF Pulsed
tpw = 100 µs
Duty Cycle = 0.1%
-20
IF - FORWARD CURRENT (mA)
0
20
40
60
80
100
TA - AMBIENT TEMPERATURE (˚ C)
Fig. 3 Normalized Radiant Intensity vs. Wavelength
Fig. 4 Radiation Diagram
1.0
NORMALIZED INTENSITY
IF =20mA
0.5
0.0
-40
1000 1500
IF =100mA
110
100
90
80
70
120
60
130
0.8
50
140
0.6
40
150
30
0.4
160
0.2
20
170
0
800
850
900
950
1000
180
1.0
1050
10
0.8
0.6
0.4
0.2
0.0
0.2
0.4
0.6
0.8
0
1.0
λλ(nm)
Fig. 5 Forward Current vs. Forward Voltage
1000
IF - FORWARD CURRENT (mA)
TA = 25˚C
100
10
1
1
2
3
4
VF - FORWARD VOLTAGE (V)
DS300338
10/31/01
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PLASTIC INFRARED
LIGHT EMITTING DIODE
QED233
QED234
DISCLAIMER
FAIRCHILD SEMICONDUCTOR RESERVES THE THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE
TO ANY PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT
ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT
DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE
RIGHTS OF OTHERS.
LIFE SUPPORT POLICY
FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD
SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical
implant into the body,or (b) support or sustain life,
and (c) whose failure to perform when properly
used in accordance with instructions for use provided
in labeling, can be reasonably expected to result in a
significant injury of the user.
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2. A critical component in any component of a life support
device or system whose failure to perform can be
reasonably expected to cause the failure of the life
support device or system, or to affect its safety or
effectiveness.
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10/31/01 DS300338