In the modern market competition, many information and entertainment resources make some emotional customers have an impulsive buying desire in a short period of time, while impulsive buying occupies a considerable part of product sales (the annual national impulse consumption has exceeded 4). Billion dollars), it naturally becomes the focus of corporate marketing activities. For today's advertising market, merchants are often not sure about the actual utility of advertising placed on media such as TV broadcast newspapers. In actual shopping situations, the more information (such as promotions) is provided, the direct potential purchase desire of customers. The stronger. Shopping car advertising is one of the forms of advertising.
At present, there are some supermarkets in China and abroad. In the car advertising, the posters are displayed on the shopping cart to instantly display the latest information (such as discounted goods) in the store. This method has the advantage of being highly visible to the customer. However, its shortcomings are also obvious. The posters attached to the shopping cart are prone to being outdated or damaged, so it is often necessary to re-create new posters, which not only increases the manpower and material resources. Waste, and technically too crude, and the interaction with customers is not strong. In order to solve this problem, a shopping mall advertising machine was designed here.
1 hardware and software design
1.1 Overall hardware module In order to reduce power consumption and speed up the design process, a dual-core structure is adopted: the main MCU functions as a switch and controls audio and video playback from the MCU (decoding chip).
The main MCU selects STC's low-cost chip STCllF01-3V3 (low supply voltage) compatible with the 8051 microcontroller. Select a 4 MHz crystal and ground the case with traces as short as possible to reduce electromagnetic emissions.
The decoding part selects the low-cost chip AM7211 of North Actions. It supports CF, SD/MMC, MS, XD card, built-in 16 MB SDRAM, supports USB OTG function, and supports multiple audio and video formats. FLASH selects SAMSUNG's 2 GB large-capacity NAND FLASH K9F2G08UOM for storing advertising information in audio and video formats. The overall circuit diagram is shown in Figure 1.
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1.2 Power Module The power supply module is shown in Figure 2. This solution uses a single 4.3 V rechargeable battery. The battery voltage is converted to each part of the chip, and the AM7211 itself integrates DC/DC to output 1.8 v and 3.3 V. In order to reduce power consumption, enhance endurance. When the shopping cart is stationary, the main decoder chip circuit and all audio and video circuits are turned off. In Figure 2, the switch chip is implemented using a VMOS tube.
1.3 Battery voltage detection module Because the nickel battery voltage is too low, it will cause permanent damage. Therefore, it is necessary to detect the battery voltage. This module consists of voltage comparator LM358, compares the reference voltage and battery voltage, and inputs its comparison value into the MCU. If the battery voltage is lower than the reference value, all audio and video will be turned off, and a low-voltage alarm signal will be generated to remind the staff. Replacement battery.
1.4 Audio Module The audio IC selects the OCA7188, which is a dual-bridge audio amplifier that drives a 4 Ω speaker at 2.7W when the supply voltage is +5 V. It has low power consumption 
Port, therefore, when the shopping cart is at rest, the MCU reduces power consumption by controlling the shutdown of the OCA7188 (off current is about O.04μA); when the chip is turned on, there is a corresponding circuit inside to avoid excessive “POP†sound. In addition, the chip package QFNl6 (4 mm × 4 mm × 0.75 mm) and SOPl6 two forms, the package is small, suitable for portable devices, the circuit shown in Figure 3.
1.5 LCD backlight driver module LCD module uses Shanghai Tianma's 5-inch display with a resolution of 320×240, which can clearly display pictures and videos. It is 54 pin cable with external interface, which corresponds to MCU motherboard. The signal connection is OK. Since the battery voltage is 4.3 V, it cannot meet the needs of its backlight power supply, so use the BOOST circuit to raise the voltage to the required voltage of the backlight, as shown in Figure 4.
1.6 Vibration Detection Module After the shopping cart is stationary or the customer leaves the shopping cart for a certain period of time, the vibration sensor sends a trigger signal to the main MCU. The main sensor senses that the shopping cart is at a standstill and sends a high-level shutdown decoder chip, which greatly reduces the Power consumption; when the shopping cart is pushed, the vibration sensor re-triggers the main MCU, emits a low level to turn on the decoding chip, and automatically loops the advertisement.
The vibration detecting component selected in this design is a low-cost mechanical vibration type. After being vibrated, the spring ball is subjected to amplitude reduction vibration for a long time, and the vibration is easily detected by the detecting circuit. The vibration output switch signal, the output impedance and the resistance value of the matched output are determined. According to the input impedance of the detection circuit, it can be made into a high-impedance output mode, as shown in Fig. 5.
2 Conclusion This study proposes a new design scheme for shopping cart car advertising machine. The prototype of this solution has been sent to the customer, and the customer has a strong interest in the product. The program has high cost performance and strong applicability, and is suitable for promotion in some large and medium-sized supermarkets.
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