As a  logistics visualized supply chain management solution provider focusing on the field of wireless communication.

The wireless sensor monitoring technology developed by the company creatively integrates the three elements of “people”, “goods” and “warehouses” in the logistics supply chain into one platform, Achieve the visibility delivered the way you want.

The main device included 4 series :

*Goods monitoring

*Assets tracking

*Vehicle tracking

*Environmental monitoring

Website : www.aovx.com 

Email: info@aovx.com

In the tracker device, we need many electronic components, the capacitor is one of them.

Today, our hardware workshop's main topic is: learn the definition and functions of the capacitor.

Capacitor definition

If the capacitance is compared to a container, the capacitance C is equivalent to the bottom area S of the container, the voltage U is equivalent to the height h of the container, and the stored energy Q is equivalent to the volume V of the container.

As we know, energy Q is the amount of current flowing in a certain period of time. Conversely, current I am equivalent to the amount of charge per unit time.

Then the capacitor charging is equivalent to we put a certain amount of charge into the container. At the same voltage level U, the greater C is, the greater the energy Q stored in the container, so that a certain current will charge it, and the longer it will take to charge to full; on the contrary, in the same time, the greater C is, The smaller the voltage level installed in the container.

In the circuits we usually come into contact with, when we charge the capacitor container, we don’t keep the same amount of charge in the capacitor every time. The amount of charge loaded each time will gradually decrease exponentially over time. This also means that the capacitor charging current will slowly decrease over time.

take daily life for example. When water is poured into a container, it will splash out. As the water level gets higher and higher, more and more water splashes out. The amount of water poured into the container will gradually decrease. When the container is full, the water poured into the container will overflow. This means that when the current charged into the capacitor container is reduced to 0, the capacitor is already full.

Functions of Capacitor

*Remove Power Supply Ripple

Similarly，take daily life for example, if you pump water directly to irrigate the field with a high-pressure pump will splash a large wave, but it is much smoother to pump the water into the water storage tower and then flow into the field. Therefore This water storage tower acts as a capacitor.

Under the same load current, the larger the capacitance, the smaller the ripple. Under the same volume of water flowing out (load current), the wider the area of the water storage tower (the larger the C), the smaller the water level drop (the smaller the ripple). We can exaggeratedly imagine that a cup and a pond will flow out with the same amount of water at the same time, and the water level of the cup will drop much faster than that of the bottom cup.

The smaller the charge and discharge cycle of the capacitor, the faster the charge and discharge frequency, and the smaller the ripple of the capacitor. If the water flows out of the water storage tower is constant and we replenish water at a frequency once a day, the water level of the water storage tower is likely to reach the bottom (large cycle and large ripple); if we replenish water in a one-minute cycle, then the water storage tower The water level may not change much (fast frequency, small ripple). In addition, according to this example, it is not difficult for us to understand that in the same case of fixed ripple, the higher the frequency, the smaller the capacitance (the smaller the water storage tower can be built, and the cost-saving).

*Let AC signals pass and block DC signals 

In fact, this is also the principle of charging and discharging. DC can't charge and discharge capacitors repeatedly, but AC can charge and discharge capacitors repeatedly.

There is an example to illustrate, that is, the power-on reset circuit, the output voltage is lagging due to the charging of the capacitor, and the RC time constant is used to determine the delay time, that is, the time required for effective reset.

In the low-level reset circuit shown in Figure 10-1(a), after the power supply VA is powered on, the rising edge of the power supply will pass through R1 and pass through C1 to the ground at the same time. Due to the high harmonic components on the rising edge, the capacitive reactance of the capacitor is very low, so it can easily pass through the capacitor to the ground. At this time, the upper end of the capacitor shows a low level; VA charges C1 through R1 until After a certain period of time, the potential on C1 rises to a high level. This period of time since VA is powered on and the duration that Reset maintains the low level triggers a low level reset. After VA is powered on, it continues a DC voltage, so that the capacitor is not in the process of charging and discharging, so the capacitor has always maintained a high level state.

The high-level reset shown in Figure 10-1(b) is also the same. The rising edge of the power supply VA at the moment of power-on passes through C2, and C2 is equivalent to a short circuit to the high-frequency component of the rising edge, so VA generates a high voltage at the upper end of R2 through a capacitor During this period, C2 is continuously charged by the power supply through R2, and the potential on R2 continues to drop until the low level state is maintained. At this time, VA is a DC voltage and C2 is blocked.

*Decoupling Interaction

Generally, nF or uF capacitors (such as 104 capacitors) are placed nearby the power supply pins of IC chips. The reason is that when the chip is working, the switching function of its digital circuit will require a slightly larger current to float immediately. Coupling capacitor, this slightly larger current change will be drawn from the power supply, and there will be a larger current change on the power supply trace from the power supply to this chip. Due to the inductance characteristics of the wire, the current change will be produced on the wire inductance. The electromotive force is induced, which causes the voltage on the line to change. In this way, the power supply of the chip is not very stable.

Next workshop we will share about how to analyze the capacitor.

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Learn more about AOVX :

The wireless sensor monitoring technology developed by the AOVX  creatively integrates the three elements of “people”, “goods” and “warehouses” in the logistics supply chain into one platform, and conducts all-around data collection and analysis for personnel, goods, and the environment in warehousing and logistics monitor.

The core members of the company's team have been deeply involved in the field of wireless communications for more than 10 years. They all come from leading companies in the communications industry and have a solid foundation for the product application and deployment at home and abroad. Based on the in-depth understanding of the Internet of Things technology and rich experience in supply chain management, AOVX is committed to helping companies implement transparent monitoring and intelligent control of many links in the logistics and transportation process, creating an efficient logistics warehousing system while satisfying customers tracking service and information needs.

Email: info@aovx.com

Website : www.aovx.com