An ultra-low-power alcohol detection controller based on the MSP430 single-chip microcomputer. The instrument is installed in a car. When the driver enters the cab, it can automatically detect the alcohol concentration to ensure the safety of driving.

The system can control whether the car igniter is turned on or off according to whether the detected alcohol content exceeds the limit. If the car exceeds the standard, the driver cannot start the car. Therefore, the emergence of drunk driving is fundamentally eliminated. The system has the advantages of high cost performance, high degree of intelligence, and stable and reliable work.

System works <br> <br> alcohol sensor system uses ultra-sensitive, ultra-low power microcontroller system, a method to automatically detect alcohol concentration, the driver can be prevented from escape detection, to determine whether the driver is driving under the influence, a system The design is shown in Figure 1. The system can be placed in the dashboard of a car. When the driver starts the car, the detector is started and the engine is locked and the car cannot start. After the alcohol sensor is heated, the detection controller detects the gas signal detected by the alcohol sensor.

Since the alcohol content is proportional to the voltage signal generated after detection by the alcohol sensor, the determination of the alcohol content can be performed based on the voltage signal. The detected signal is amplified and filtered. It is converted into a digital signal by the built-in 12-bit ADC. The signal is processed by the MCU. Assuming that the alcohol content is not exceeded, the LCD display shows the current alcohol concentration, and the normal indicator lights up. , control relay does not work, the car starts;

On the contrary, an audible and visual alarm is performed to control the relay to cut off the power supply of the ignition device, and the driver cannot start the car and fundamentally realize the control of drunk driving. After the car is started, the controller immediately enters a low-power state, and only the alcohol concentration detection circuit has been operating. Once the driver drinks during driving, the controller immediately returns to normal operation.

System hardware design
1. Master control circuit design

The controller uses the MSP430FG4619 16-bit ultra-low power, high-performance MSP430 microcontroller series introduced by Texas Instruments. It is only 350μA in active mode and the maximum input leakage current is 50nA; its high degree of integration not only greatly reduces the failure rate, but also has obvious advantages in terms of cost, volume, and stability.

The MSP430FG4619 in the alcohol detection control system is used to determine the alcohol content in the gas and control the operation of the entire controller. System control circuit shown in Figure 2, including the crystal oscillator circuit, reset circuit and JTAG interface circuit.

2. Alcohol Alcohol <br> <br> detection circuit detection circuit is amplified by an alcohol sensor with high accuracy, the signal conditioning circuit, a filter circuit 12 and microcontroller built ADC and other components, as shown in FIG. The main function is to detect the alcohol content and determine whether it exceeds the standard.

The alcohol sensor uses the side-heat type semiconductor alcohol gas sensor MQ3. It has high sensitivity and good selectivity to ethanol vapor, fast response recovery, long-term life and reliable stability, detection range is 10 ~ 1000ppm, Especially suitable for the detection of drink drivers.

The signal conditioning amplifier preamplifier is implemented using the MAX4238 high-precision op amp produced by Maxim, which has a bias current of 1pA, a bias voltage of 2μV, ultra-low temperature drift, and good performance. The post-amplification is realized by commonly used OP07C operation amplification. The filter chip is implemented by MAX266, a switched-capacitor pin-programmable integrated filter produced by Maxim, and has better performance than the ordinary RC filter circuit.

A/D conversion adopts the 12-bit ADC with the maximum rate of 200KSPS that comes with the MSP430FG4619IPZ. Its voltage reference can be selected as an internal reference or an external reference, which saves the external ADC chip and greatly simplifies the design of the hardware while meeting the accuracy. Requirements, so it is very suitable for the design of this system.

3 light and liquid crystal display circuit

The indicator circuit has three indicators: red, green, and yellow. The red indicator is the power indicator and is on during operation. The green indicator is a warning indicator. The alcohol probe requires a certain amount of time for heating to achieve the desired sensitivity. The heating time is up and the green light is on. Said that the concentration can be detected; yellow light for the alarm indicator, the yellow light is off, that can drive; when the yellow light, that alcohol concentration exceeded, can not drive, while the higher the frequency of yellow light flashes, the higher the alcohol concentration.

The liquid crystal display circuit is used to display the concentration of the measured alcohol. The liquid crystal display circuit adopts LCM128645ZK, which is a low-power dot-matrix graphic LCD that can work under the condition of 3.3V power supply. The display format is 128 (columns)×64 (rows), with multi-function instructions, internal There is a Chinese character library that can work both in serial mode and parallel mode. It is easy to connect to a 16-bit microcontroller. The connection to the microcontroller in this system uses a parallel operation mode, as shown in Figure 4.

4. Relay control circuit

This circuit is controlled by the single-chip microcomputer P2.4, which is equivalent to the switch, controls the opening and closing of the ignition device, the lighting of the lights, and the sound of the speakers. It is a very important execution unit in the system. The circuit is simple. For reasons of space, this is not given here.

5. Alarm and keyboard circuit

Using the buzzer as an alarm, when the alcohol content exceeds the standard, a warning signal for prohibiting driving is issued; when it does not exceed the standard, the driving permission sound is issued. This is achieved by the P1.7 driver buzzer.

Because the microcontroller has enough I/O pins, the system's keyboard circuit uses a stand-alone keyboard, as shown in Figure 4. By using the interrupt mode, you can set the system parameters of the alcohol detection controller, such as the alarm concentration of the alcohol concentration.

6. Other circuits

The JTAG interface circuit is used to debug programs and upgrade system software. The power conversion circuit is used to convert the power supply system on the vehicle into the voltage required by the microcontroller and the chip used by the system. The monitoring reset circuit is used to ensure that the microcontroller is in a good state of operation, to prevent the program from running due to interference, and more reliable than the internal watchdog circuit.

Through the above design, the front end of the system can determine the alcohol content signal detected by the alcohol sensor and generate a corresponding control signal to control the ignition circuit of the automobile through the judgment of the single-chip microcomputer, so as to achieve effective control of drunk driving.

software design

The software part is modularly programmed according to system functions. Alcohol content detection, alcohol content exceeds the standard, alcohol content display, sound and light alarm and other functions. After the system is initialized, the alcohol sensor is heated to automatically enter the measurement state, and then the alcohol content voltage signal is collected and compared with the set precision concentration. If the concentration is higher than this concentration, the concentration is displayed, and the sound and light alarm is performed and the cutoff is performed. In the ignition circuit, the driver cannot start the car; if it is lower than this concentration, the measured concentration is displayed and the engine is started.

Conclusion <br> <br> car alcohol detectors for the prevention of traffic accidents situation and design. This article introduced the entire design through the description of various circuit functions and software workflows. As the system is installed in a car, automatic measurement, high degree of intelligence, low power consumption, has a good effect on prevention of drunk driving, and has a very good promotion value in practical applications.