Introduction:

As a beginner in the PCB field, have you ever looked at a circuit diagram and thought, “Oh my god! Am I completely clueless? Why can’t I understand these diagrams? Why am I even taking this course?”

I think many people experience the same confusion. When faced with dense, crisscrossing lines, it’s hard to know where to begin. The truth is, circuit diagrams are not as complex as they appear. The key is not to be intimidated by their appearance. Common circuits we encounter daily include electronic circuits, amplification circuits, crystal oscillators, and power circuits. Below are some circuit diagrams you might encounter in everyday life.

Figure 1:

Note:
①
The numbers in【】in this circuit diagram represent the signal path.

②
》
in this circuit diagram represents the signal pattern.

③
《》
in this circuit diagram indicates a bidirectional signal pattern.

Let’s start by examining the circuit diagram above. It represents the electronic compass and accelerometer in a smartphone, which functions similarly to a physical compass. Smartphones use this to determine their location. The circuit diagram below is slightly more complex. If the electronic compass is malfunctioning, we would first check whether the voltage circuit is operating normally. If the voltage is fine, we would next verify the I2C bus signal, which can help us determine whether there is an issue with the U801 chip.

Figure 2:

IR (infrared) technology is now widely used in electronic products due to its convenience, simplicity, and practicality. It is an essential feature in smartphones, remote controls, smart TVs, and many other devices. This circuit is composed of the IR control chip U802, power supply chip U808, and the IR LED diode.

If there is an issue with the IR system, we would first check the voltage output of the U808 power supply chip. If this is normal, we would then examine the signal from the U802 control chip. If all signals are functioning correctly, the last step is to check if the IR LED diode is damaged.

My approach to understanding circuit diagrams is to break them down into manageable sections instead of attempting to understand the entire diagram at once. With the right strategy, circuit diagrams are far easier to comprehend than they seem at first.

Figure 3:

EMMC (embedded MultiMediaCard) is the storage memory found in smartphones, with capacities like 16GB, 32GB, 64GB, 128GB, and so on. The circuit here is relatively simple. If there’s an issue with this circuit, we would first inspect the power supply circuit, then analyze the signal circuit, focusing on the EMMC and CPU ICs. Typically, if the CPU is malfunctioning, it’s not cost-effective to repair it due to the high cost of replacement.

Figure 4:

The Sensor-GYRO in a smartphone is a device that detects and maintains orientation based on the conservation of angular momentum. This function is essential and plays a critical role in smartphones.

Figure 5:

Hall Effect Switch: When a metal or semiconductor with current is placed perpendicular to a magnetic field, a potential difference between the two ends of the material is generated. This phenomenon is known as the Hall Effect. For instance, a magnetic disk in a phone case causes the screen to turn off when the case is closed.

Figures 6 & 7: