Using a reflective near-infrared sensor and a voice recording and playback component, a car reversing collision avoidance voice prompt device was studied. When a car is reversing, as long as there is a person or object within a certain distance from the rear of the car, a portion of the infrared light signal will be reflected back by the person or object. This signal is received by a photosensitive receiver tube installed in the same row as the transmitter tube and converted into an electrical signal of the same frequency. After amplification, demodulation, shaping, comparison, and processing by the internal circuit of the module, a control signal is output at the output terminal to control the voice recording and playback component to work, informing the driver that there is a person or object behind the car. Since the near-infrared sensor and the voice recording and playback component are both integrated structures, they are low in cost, simple in wiring, have strong shock resistance, accurate in measurement, and stable and reliable in operation, making them suitable for installation and use in automobiles.
introduction
With the continuous development of science and technology, and the emergence of new technologies, materials, processes and devices, people have conducted in-depth research and development on infrared optics. In order to achieve automation, save manpower, improve efficiency, increase equipment functions, ensure safety, protect the environment, and save resources and energy, infrared sensors, which resemble human eyes, play a particularly important role. As early as 1972, televisions using infrared remote control were introduced. Especially after 1990, near-infrared sensors were successfully applied to various fields. Near-infrared sensors use 940nm light waves as a carrier for transmission and reception.
This paper studies a car reversing collision avoidance voice prompt device. It utilizes a reflective infrared transmitter and receiver module (TX05D) as an object recognition sensor. When a person or obstacle appears behind the car while reversing (e.g., when parking close to a wall, turning around in a narrow space, etc.), the voice recording and playback component can issue a warning that someone or an obstacle is behind the vehicle, alerting the driver (due to blind spots in the rearview mirror). This improves vehicle safety. The voice prompt system uses a voice recording and playback component that can record and play audio 100,000 times repeatedly. The stored audio can be preserved for 100 years after power failure. It offers good sound quality, low cost, and simple wiring, providing great convenience to users. The power supply uses the car's 12V battery and a 6V voltage regulator, making it both economical and convenient. The device's features include:
It has strong anti-interference ability, stable and reliable operation, voice prompts, and a measurement distance of 1.2m, making it suitable for installation and use in automobiles.
1. Module Structure and Working Principle
1.1 Reflective Near-Infrared Sensor TX05D
The TX05D's appearance and wiring are shown in Figure 1. It has an integrated structure, making it very convenient to use. All circuits are soldered into a single 46mm×32mm×17mm plastic box (excluding the mounting bracket D). The side of the box features a status indicator light and a sensitivity adjustment hole. A red LED indicates the near-infrared sensor's operating status; it is normally off and illuminates when there is a reflective object. The sensitivity adjustment hole adjusts the reflection detection distance; clockwise adjustment increases the distance, and counter-clockwise adjustment decreases it. The TX05D uses a 1.5m double-core shielded cable as its output lead. The red wire is the positive power supply, and the white wire is the output. The shielding wire (copper mesh D) is connected to the negative power supply. Within the effective detection range of the near-infrared sensor, if a person or object is present, the voltage on the white wire at the output is high; if there is no reflective object, the output is low. In practical applications, if the lead length is insufficient, it can be lengthened as needed.
The TX05D operates at a voltage of 5~12V, with a maximum voltage of 15V. Its operating current is 5~20mA, with a maximum of 30mA. The detection distance is 1.2m. The TX05D works by emitting a 38kHz modulated infrared signal from its internal infrared emitter. When someone enters (or an object is present) within the effective detection range, a portion of the infrared signal is reflected back. The infrared receiver converts this reflected signal into an electrical signal of the same frequency, which is then amplified, demodulated, shaped, and compared before being output as a high-level signal. Because the TX05D uses modulation technology and imported compensated anti-interference devices, it effectively mitigates interference issues to some extent.
1.2 Voice Recording and Playback Component IDD1110/1420
The ISD series voice recording and playback components use the state-of-the-art ISD series monolithic voice processing integrated circuit chip from ISD Corporation of the United States as their core, incorporating memory, a noise-canceling microphone preamplifier and automatic gain control circuitry, a dedicated voice filtering circuit, a clock oscillation circuit with extremely high temperature stability, and all voice processing circuitry. It achieves full surface mount miniaturization, excellent sound quality, and robust durability.
The ISD series voice recording and playback components can be used in various one-piece voice messaging, voice alarm, and voice prompt devices. This component can retain information for a long time even when the power is off, and the recorded content can be easily modified. The component is compact, has a wide range of applications, and is extremely convenient. The component operates at a voltage of 4.5~6.5V, with a typical quiescent current of 0.5mA and a working current of 25mA. Recording and playback times are 10~20 seconds. It permanently stores information for 100,000 recordings and can retain data for 100 years. It is easy to use, requires no programming or system development, and allows for easy modification of recorded and played-out content. Recording is done with a standard electret microphone, and playback is done with an 8~16Ω speaker.
2. Wiring diagram for car reversing collision avoidance voice prompt system
The wiring diagram is shown in Figure 2. It consists of a near-infrared sensor, a voice recording and playback component, and a power supply. In Figure 2, IC1 can be a 7806 integrated voltage regulator, IC2 is a TX05D near-infrared sensor (Tianjin Texin Electronics Factory), IC3 is an ISD1420 voice recording and playback component (recording and playback time is 20 seconds), and KS is an HRM2H relay. All other components are provided by the manufacturer and do not need to be purchased. In actual application, the TX05D is installed in the middle of the rear of the car, with its transmitter and receiver facing backwards. The -12V lead is connected before the reversing lights. This way, when the car reverses, the circuit automatically powers on and operates along with the reversing lights.
3. Operation process
3.1 Recording
When the power is connected, the circuit automatically enters power-saving preparation mode. Press and hold the REC recording button to enter recording mode; the recording indicator light (LED) will illuminate until the memory is full or the REC button is released. Recorded content can include phrases such as "Driver, please note there is someone behind the vehicle; there is an obstacle behind the vehicle."
3.2 Playback
There are several playback modes. Touching the PE (playe) button initiates playback until it ends. Alternatively, pressing the PL (playl) button initiates playback until it ends or the playl button is released. The L terminal of the voice recording and playback component can also be connected to VCC; pressing the PL (playl) button initiates loop playback, and releasing it stops it. This system uses loop playback. When a person or object is behind the vehicle, IC2 (TX05D) outputs a control signal, transistor VT (9013) conducts, and relay KS (HRM2H) closes its working contacts. One switch connects VCC to the L terminal, while another switch short-circuits the PL (playl) button to ground, causing the voice recording and playback component to loop. When the person or object leaves, IC2 outputs a low level, VT cuts off, KS releases, and the normally open contact closes, stopping the playback.
