Design and implementation of solar quartz clock

Batteries are closely related to our lives and work. For example, quartz clocks (pointer type) used in homes and offices generally use No. 5 batteries as power sources. According to relevant statistics, China's annual battery production is about 15 billion pieces, making it a major producer in the world, and its annual consumption is about 5 billion pieces, making it a major consumer in the world, and there is a trend of increasing. For many years, a huge number of waste batteries have been discarded with garbage in my country, and the treatment methods are either incineration or landfill.

Everyone knows that the five metals that pose the greatest threat to the natural environment are chromium, cadmium, copper, lead, and mercury, of which batteries account for three of them: mercury, lead, and cadmium. If burned, they pollute the atmosphere; if landfilled, they pollute the soil and are harmful to crops; if they pollute water sources, they are harmful to aquatic organisms (fish and shrimp, etc.). According to information: a small button battery can pollute 600,000 liters of water, which is equivalent to the amount of water a person drinks in his lifetime; a No. 1 battery rots in the ground, which can make one square meter of land lose its use value and cause permanent pollution.

Humans cannot live without the earth, nor can they live without food. These toxic heavy metals enter the human body through various channels (breathing through the nose and mouth, eating vegetables, fish and shrimp, etc.), and are difficult to eliminate after long-term accumulation. The medical community has confirmed that mercury can seriously harm the human nervous system, especially children; cadmium can cause osteoporosis, bone deformation, bone pain, etc., and cause liver and kidney damage; lead is the most difficult to excrete after entering the human body, and it interferes with kidney function and reproductive function. It can cause abnormal behavior and low IQ in children.

Since the harm caused by used batteries to humans has become an indisputable fact, how do other countries in the world deal with it? In some Western countries in Europe (such as Germany), used batteries have long been classified as hazardous and toxic waste. Battery dealers must recycle them through the "collecting old and selling new" method, and they must not be discarded in nature at will.

In my country, although a few environmentalists have learned from the experience of some Western countries and advocated the classified collection of used batteries, on the one hand, the government has no clear regulations on the disposal of used batteries, and on the other hand, people have a low level of awareness of the harm of used batteries and do not pay enough attention to it; they are not enthusiastic about the collection of used batteries and the number of participants is small. This paper proposes a green, environmentally friendly and energy-saving power supply that replaces traditional No. 5 batteries with solar panels, supercapacitors, and charge pumps (LM2788-2.0) as core components. It is applied to quartz clocks, avoiding the pollution of the environment by used No. 5 batteries from the source, and will play a positive role in protecting the environment and keeping our green home.

1 Component Description

The circuit is composed of four core components: solar panels, super capacitors, charge pumps, and Schottky diodes.

(1) The solar panel is made of polycrystalline silicon, with dimensions of 60 mm in length, 44 mm in width, and 3 mm in thickness; output electrical parameters: operating voltage 5.5 V, operating current 60 mA, and rated power 0.33 W, see Figure 1.

(2) The supercapacitor parameters are 120F/2.3V. Its characteristics are fast charging, long life, high efficiency, large capacity, and good temperature adaptability. In addition, each link of production, use, storage, and disassembly is pollution-free, as shown in Figure 2.

(3) Charge pump LM2788-2.0 is an 8-pin step-down charge pump DC/DC converter. Input 2.6V~5.5V, output 2.0V. The main features of this converter are: output voltage accuracy: 2.0V±5%, output current up to 120mA; maximum conversion efficiency up to 90%; low power consumption, working current 32μA; with shutdown control, power consumption is only 0.1μ in the shutdown state; overheating and short circuit protection, see Figure 3.

(4) The Schottky diode 1N5819 is characterized by large current (1A), low voltage drop (0.3V), and high withstand voltage (40V), see Figure 4.

2 Circuit Working Principle

Hang the quartz clock in a brightly lit place indoors. See Figure 5 for the circuit schematic.

During the day, indoor light diffuses on the solar panel, generating current, which is converted by the charge pump LM2788-2.0 to output a voltage of 2.0V; after being isolated by the Schottky diode 1N5819, it supplies power to the quartz clock on the one hand and charges the supercapacitor on the other hand (the upper limit of the voltage across the capacitor is Uh=Uout-Ud1=2.0-0.3=1.7V). At night, the solar panel does not generate current, and the electric energy stored in the supercapacitor supplies power to the quartz clock. The function of the Schottky diode D1 is to prevent the electric energy stored in the supercapacitor from flowing back into the charge pump and the solar panel when the solar panel is not generating electricity (at night or on cloudy days).

According to the national standard for quartz clocks: the working voltage range of quartz clocks is generally 1.25~1.70V; the average power consumption current of the measured quartz clock jump second (intermittent) quartz clock is about 125μA. When the supercapacitor voltage drops from 1.7V to 1.25V, the amount of electricity that can be released is △Q=CUh-CUL=C(Uh-UL)=120×(1.7-1.215)=54C; if this amount of electricity is output according to the average current I=150μA, it will take time t=△Q/I=54/(150×10-6)=3.6×105s=100h to be consumed. Through calculation, the time is guaranteed to ensure the backup power for the quartz clock to work at night. The modified quartz clock is shown in Figure 6.

The specifications or models of components used in the circuit schematic are shown in Table 1.

3 Circuits highlight the green theme

The design of the quartz clock using green energy closely grasps the theme of green, environmental protection and energy saving, and effectively solves the harm of ordinary batteries to human body, soil, water source, etc. Its features are as follows:

(1) Energy acquisition is green

As we all know, sunlight is inexhaustible. Converting sunlight directly into electricity to replace batteries as the energy source of quartz clocks is conducive to slowing down the rate of global warming and environmental degradation, and reflects that low-carbon life starts from small things around us. It is better to practice half a step than to advocate verbally.

(2) Energy storage is environmentally friendly

Alkaline batteries have the shortest service life, and rechargeable batteries (lithium-ion, nickel-metal hydride) have a shorter service life (several hundred cycles). Supercapacitors have the advantages of large capacity, long service life (nearly a million cycles), maintenance-free, economical and environmentally friendly.

(3) Energy use is efficient

The energy storage of rechargeable batteries (lithium-ion, nickel-metal hydride) is through the process of electrical energy → chemical energy → electrical energy, and the conversion efficiency is low. The supercapacitor selected in this circuit is a new type of energy storage device. It does not undergo chemical energy conversion, so it is of course highly efficient and energy-saving. In addition, the traditional voltage reduction method of obtaining the required working voltage by dividing the DC power supply voltage also has low conversion efficiency. This circuit uses the charge pump LM2788-2.0 to manage the power supply, which improves the utilization rate of electrical energy and also reflects energy saving.

4. Realize Value

According to the sixth national census in 2010, there are more than 400 million households in 31 provinces, autonomous regions and municipalities, and most of them use quartz clocks for timekeeping. According to conservative estimates, there are at least 400 million quartz clocks in households across the country, consuming 800 million ordinary batteries each year. If quartz clocks in 100 million urban households use green energy, the protection of the environment is obvious. Because this circuit is low-cost, it has certain promotion and use value.