Understanding the TSOP-1738 IR Receiver
What is the TSOP-1738?
The TSOP-1738 is a miniaturized IR receiver module that consists of a photodetector, amplifier, automatic gain control, bandpass filter, demodulator, and output stage integrated into a single package. It is designed to receive modulated infrared signals with a carrier frequency of 38 kHz, which is commonly used by many remote control systems.
TSOP-1738 Pinout and Package
The TSOP-1738 comes in a 3-pin through-hole package with the following pinout:
| Pin | Name | Description |
|---|---|---|
| 1 | OUT | Output signal |
| 2 | GND | Ground |
| 3 | VS | Supply voltage (2.5V to 5.5V) |
The package dimensions are approximately 6.0 x 4.7 x 5.6 mm (L x W x H), making it compact and easy to integrate into various circuit designs.
Operating Characteristics
The TSOP-1738 has the following key operating characteristics:
| Parameter | Value |
|---|---|
| Supply Voltage | 2.5V to 5.5V |
| Current Consumption | 0.35mA to 1.5mA |
| Carrier Frequency | 38 kHz |
| Reception Range | Up to 45 meters |
| Output Logic | Active low |
| Operating Temperature | -25°C to +85°C |
These characteristics make the TSOP-1738 suitable for a wide range of applications and ensure reliable operation under various conditions.
Connecting the TSOP-1738 in IR Receiver Circuits
Basic Connection Diagram
To use the TSOP-1738 in your IR receiver circuit, follow this basic connection diagram:
+3.3V/+5V
|
|
|‾|
| | 1kΩ
|_|
|
|
TSOP-1738 |
OUT ---*--- To Microcontroller/Arduino
GND ------- GND
VS -------- +3.3V/+5V
In this diagram, the OUT pin is connected to a microcontroller or Arduino input pin through a 1kΩ current-limiting resistor. The GND pin is connected to the ground, and the VS pin is connected to a 3.3V or 5V power supply, depending on your system requirements.
Pull-up Resistor Configuration
Since the TSOP-1738’s output is active low, you may need to use a pull-up resistor to ensure a stable high level when no IR signal is received. Here’s how to modify the basic connection diagram to include a pull-up resistor:
+3.3V/+5V
|
|
|‾|
| | 1kΩ
|_|
|
|
TSOP-1738 |
OUT ---*--- To Microcontroller/Arduino
|
|‾|
| | 10kΩ
|_|
|
GND
GND ------- GND
VS -------- +3.3V/+5V
In this configuration, a 10kΩ pull-up resistor is connected between the OUT pin and the power supply. This ensures that the output is pulled high when no IR signal is detected, providing a clear distinction between the idle state and the active low state when an IR signal is received.
Filtering and Decoupling
To minimize noise and ensure stable operation, it’s a good practice to add a ceramic capacitor (0.1μF to 1μF) between the VS and GND pins of the TSOP-1738. This capacitor helps filter out high-frequency noise and provides local decoupling for the IR receiver.
Additionally, you can add a small capacitor (10pF to 100pF) between the OUT pin and ground to filter out any residual carrier frequency components and improve the signal quality.
Here’s the updated connection diagram with the filtering and decoupling components:
+3.3V/+5V
|
|
|‾|
| | 1kΩ
|_|
|
|
TSOP-1738 |
OUT ---*--- To Microcontroller/Arduino
|
|‾|
| | 10kΩ
|_|
|
=== 10pF to 100pF
GND
GND ------- GND
|
=== 0.1μF to 1μF
|
VS -------- +3.3V/+5V
Interfacing with Microcontrollers and Arduinos
Arduino Example
Here’s a simple Arduino sketch that demonstrates how to read IR signals using the TSOP-1738:
#include <IRremote.h>
const int IR_RECEIVE_PIN = 2;
IRrecv irrecv(IR_RECEIVE_PIN);
decode_results results;
void setup() {
Serial.begin(9600);
irrecv.enableIRIn();
}
void loop() {
if (irrecv.decode(&results)) {
Serial.println(results.value, HEX);
irrecv.resume();
}
}
In this example, we use the IRremote library to simplify the process of decoding IR signals. The IR_RECEIVE_PIN constant defines the Arduino pin connected to the TSOP-1738’s OUT pin.
In the setup() function, we initialize the serial communication and enable the IR receiver using irrecv.enableIRIn().
The loop() function continuously checks for incoming IR signals using irrecv.decode(&results). If a signal is received, the decoded value is printed to the serial monitor in hexadecimal format, and irrecv.resume() is called to prepare the receiver for the next signal.
Other Microcontrollers
The process of interfacing the TSOP-1738 with other microcontrollers, such as PIC, AVR, or STM32, is similar to the Arduino example. You’ll need to configure an input pin to read the TSOP-1738’s output signal and use appropriate libraries or custom code to decode the received IR data according to your specific microcontroller and programming environment.
Applications and Projects
The TSOP-1738 IR receiver can be used in a wide range of applications and projects, such as:
- Remote-controlled devices (e.g., robots, drones, home automation systems)
- IR communication systems
- Wireless sensor networks
- IR-based proximity and obstacle detection
- IR-based data transmission
By incorporating the TSOP-1738 into your projects, you can add IR remote control functionality, enable wireless communication, or detect objects using IR signals.
Troubleshooting and Tips
- Ensure that the TSOP-1738 is properly connected according to the pinout and connection diagrams provided.
- Verify that the power supply voltage is within the specified range (2.5V to 5.5V) and is stable.
- Use appropriate current-limiting and pull-up resistors as described in the connection diagrams.
- Include filtering and decoupling capacitors to minimize noise and improve signal quality.
- Ensure that the IR transmitter and receiver are within the specified reception range and have a clear line of sight.
- Use reliable and well-documented libraries for your specific microcontroller or programming environment to simplify the IR decoding process.
Frequently Asked Questions (FAQ)
1. What is the maximum distance at which the TSOP-1738 can receive IR signals?
The TSOP-1738 has a reception range of up to 45 meters, depending on factors such as the strength of the IR transmitter, ambient light conditions, and any obstructions between the transmitter and receiver.
2. Can I use the TSOP-1738 with 3.3V microcontrollers?
Yes, the TSOP-1738 is compatible with both 3.3V and 5V microcontrollers. The VS pin can be connected to either a 3.3V or 5V power supply, as long as it is within the specified operating voltage range of 2.5V to 5.5V.
3. What is the purpose of the pull-up resistor in the connection diagram?
The pull-up resistor ensures that the TSOP-1738’s output is pulled high when no IR signal is received. This provides a clear distinction between the idle state (high) and the active low state when an IR signal is detected, making it easier for the microcontroller to interpret the received data.
4. How can I filter out ambient IR noise in my environment?
To minimize the impact of ambient IR noise, you can:
- Use the TSOP-1738 with a 38 kHz carrier frequency, as it is less common in natural and artificial light sources.
- Ensure that the TSOP-1738 is not directly exposed to strong IR sources, such as sunlight or incandescent bulbs.
- Use shielding or physical barriers to block unwanted IR signals from reaching the receiver.
- Implement software filtering techniques, such as checking for valid IR protocols or using a specific encoding scheme for your application.
5. Can I use multiple TSOP-1738 receivers in the same circuit?
Yes, you can use multiple TSOP-1738 receivers in the same circuit, as long as each receiver is connected to a separate microcontroller input pin. This allows you to create multi-channel IR communication systems or enable IR reception from different directions.
By following this comprehensive guide, you should now have a solid understanding of how to connect and use the TSOP-1738 IR receiver in your circuits. Whether you’re building a remote-controlled robot, a home automation system, or any other project that requires IR communication, the TSOP-1738 is a reliable and easy-to-use solution.
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