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Infrared Transmitter and
Receiver Block Design
3/29/05 Kevin Erickson
1
IR Transmitter
Block Architecture
Digital Audio
sampled at 44.1 kHz
ADC
Block
16 bit serial data
Infrared Emitter
Driver
16 bit serial data sent
via Infrared Emitter
0101010
The input is a
series of 0’s and
1’s from the
ADC block.
3/29/05 Kevin Erickson
The output is infrared
pulses of the 0’s and 1’s
sent to a photodiode in
the IR Receiver
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IR Transmitter Schematic
•5 Volt supply to operate
provided by transmitter
power supply block
•Digital audio data input
from ADC block
•D1 is an infrared
emitting diode
•R1 is a current limiting
resistor thru the infrared
emitter
•C1 is a speed up
capacitor
2 circuits needed
(left and right channel)
3/29/05 Kevin Erickson
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IR Transmitter
Key Component Selection
Components:
– Infrared emitter
• Ability to transmit 20 feet (high forward current)
• Fast switching time
– Current limiting resistor
• Power and heat dissipation
– Transistor
• Fast switching time
• Ability to handle short bursts of 1A
3/29/05 Kevin Erickson
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Infrared Transmitter
Key Components
• HDSL-4420 Infrared Emitter Characteristics
–
–
–
–
–
–
–
–
–
–
–
Peak Forward Current (pulse width 100μs): 500 mA
Continuous DC Forward Current: 100 mA
Power Dissipation: 100 mW
Transient Forward Current (10 ms Pulse): 1.0 A
Forward Voltage: 1.30 – 1.70 V
Reverse Voltage: 5 – 20 V
Series Resistance: 2Ω
Viewing Angle: 24° (±12°)
Peak Wavelength: 850 – 900 nm
Optical Rise and Fall time: 40 ns
Bandwidth: 9 MHz
3/29/05 Kevin Erickson
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IR Transmitter
Key Component Selection
• Current Limiting Resistor
– 20Ω carbon film resistor
– ½ Watt
R1  VCC  VF  VDS ( on)  / I F (Continuous)
R1

5  1.7  1.5V

100mA
R1  20
P  I F2  R
P  100mA2  20
P  200mW
3/29/05 Kevin Erickson
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IR Transmitter
Key Component Selection
• 2N7002 N-Channel Enhancement Mode FET
– ID Maximum Drain Current – Continuous 115 mA
– Pulsed 800 mA
– PD Maximum Power Dissipation: 200 mW
– VDS(ON) Drain-Source On-Voltage: 0.09 – 1.5 V
– ID(ON) On-State Drain Current: 500 – 2700 mA
– ton Turn-On Time: 20 ns
– toff Turn-Off Time: 20 ns
3/29/05 Kevin Erickson
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Infrared Transmitter
Bill of Materials
Manufacture ID
Number
Reference to
Schematic
Cost
Infrared emitter--880nm Peak emission
±12° Half angle
40ns Switching times
D1
$1.32
Kemet
C315C473M5U5CA
0.047 μf Capacitor
50 Volt
± 10% tolerance
C1
$0.36
2
Yageo
CFR-50JB-20R
20 Ohm carbon film resistor
½ Watt
1% tolerance
R1
$0.02
4
2
Yageo
CFR-25JB-1K0
1 kΩ Ohm carbon film resistor
¼ Watt
± 5% tolerance
R2
$0.02
5
2
Yageo
CFR-25JB-22R
22 Ohm carbon film resistor
¼ Watt
± 5% tolerance
R3
$0.02
6
2
Fairchild Semi
2N7002
N-Channel Enhancement Mode FET
Power MOSFET gate drivers
10ns Switching times
Q1
$0.50
Total
$2.24
Item #
Qty
1
2
Agilient
HSDL-4420
2
2
3
3/29/05 Kevin Erickson
Attributes
8
IR Receiver
Block Architecture
16 bit serial data sent
via Infrared Emitter
Photodiode
Transimpedance
Amplifier
16 bit serial data to
DAC block
Comparator
DAC
0101010
Photodiode receives
the infrared signal and
converts the light
signal to current
3/29/05 Kevin Erickson
The transimpedance
amplifier is needed to
convert the current into
an amplified voltage
Comparator is used to
create the 5 Volt logic
(0’s and 1’s) needed by
the ADC block
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IR Receiver Schematic
2 circuits needed
(left and right channel)
Transimpedance
Amplifier
Comparator
Photodiode
•D1 is a
photodiode
(λ=880-950nm)
3/29/05 Kevin Erickson
•U1 creates the
transimpedance
amplifier
•U2 is a 5V
comparator for 5V
logic.
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IR Receiver
Key Component Selection
Components:
– Photodiode
• Fast switching time
• Able to receive infrared signal 20 feet away
– Comparator
• 0-5 Volt logic output
3/29/05 Kevin Erickson
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Infrared Transmitter
Key Components
• HDSL-5420 Photodiode Characteristics
–
–
–
–
–
–
–
–
–
Short Circuit Current: 4.3 μA
PhotoCurrent: 3.0 – 6.0 μA
Power Dissipation: 150 mW
Forward Voltage: 0.8 V
Series Resistance: 2000Ω
Viewing Angle: 28° (±14°)
Peak Wavelength: 850 – 900 nm
Optical Rise and Fall time: 7.5 ns
Bandwidth: 50 MHz
3/29/05 Kevin Erickson
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IR Receiver
Transimpedance Amplifier
Typical ISC = 4.3μA from
photodiode spec. sheet
ISC
Vout  I SC  R1
Vout  4.3A 1M  4.3V
3/29/05 Kevin Erickson
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Infrared Receiver
Bill of Materials
Reference to
Schematic
Cost
Item #
Qty
Manufacture ID
Attributes
1
2
HSDL-5420
875nm Peak emission
±14° Half angle
7.5ns Switching times
D1
$1.08
2
2
LM741CN
General purpose op-amp
U1
$1.08
3
2
LMV331
5 Volt Comparator
5V logic output
U2
$1.60
4
2
CFR-25JB-1M0
1 MΩ Ohm carbon film
¼ Watt
± 5% tolerance
R1
$0.02
Total
$3.78
3/29/05 Kevin Erickson
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