Resistors are common electronic components in circuits. They restrict the flow of electrons, thereby altering parameters such as current, voltage, and power. Resistors play a crucial role in electronic devices and circuits; therefore, understanding their function and working principle is essential. This article will detail the function and working principle of resistors.
The function of resistor
1. Limit current
The most basic function of a resistor is to limit the flow of current. The magnitude of the current is determined by the voltage and the resistance. According to Ohm's law, current equals voltage divided by resistance. Therefore, when the resistance increases, the current decreases, and vice versa. This is the most common application of resistors in electronic circuits.
2. Voltage divider
A voltage divider is a circuit composed of multiple resistors that divides a single voltage into several smaller voltages. The principle behind a voltage divider is based on the proportional relationship between resistors. When resistors with different resistance values are connected in series, the voltage is distributed according to their resistance ratio. Voltage dividers have a wide range of applications; for example, they can be used in the feedback circuits of amplifiers to generate feedback signals.
3. Filter
A filter is an electronic circuit used to remove noise or interference signals from a circuit. As a passive component of a filter, a resistor can be used to control the degree of attenuation. The RC circuit, consisting of a resistor and a capacitor, is the most common type of filter circuit.
4. Temperature sensor
Resistors can also be used to make temperature sensors. The resistance value of a resistor is related to temperature; when the temperature changes, the resistance value of the resistor also changes accordingly. This phenomenon is called the temperature coefficient of resistance. Various types of temperature sensors can be made using the temperature coefficient of resistance, such as thermistors and thermocouples.
5. Protect components
Resistors can also be used to protect other components in a circuit. For example, when a large voltage pulse is applied to a circuit, it may damage other components. However, if a resistor is placed in the circuit, it can limit the current, thus protecting other components from damage.
6. Correction circuit
Resistors can be used to calibrate circuits. For example, calibration is often required when measuring current or voltage to ensure the accuracy of the measurement results. Resistors can be used to correct the readings of instruments or measuring devices, thereby improving their accuracy.
7. Diverter
A shunt is a circuit composed of multiple resistors that divides a current into several smaller currents. The principle of a shunt is based on the proportional relationship between their resistances. When resistors with different resistance values are connected in parallel, the current is distributed according to their resistance ratio. Shunts have a wide range of applications, such as distributing current across multiple loads in a circuit.
8. Signal Conversion
Resistors can also be used for signal conversion. For example, when a circuit needs to convert a voltage signal into a current signal, a resistor can be used as a converter. By adjusting the resistance value, the magnitude of the output current can be controlled to be proportional to the magnitude of the input voltage signal.
9. Circuit attenuator
Resistors can also be used as circuit attenuators. In some cases, it is necessary to reduce the strength of the input signal to suit specific applications. A circuit attenuator is a passive electronic component that reduces the strength of the input signal to make it suitable for a particular application.
10. Circuit isolation
Resistors can also be used for circuit isolation. In some cases, it is necessary to isolate signals or energy in a circuit to avoid potential problems or damage. Circuit isolators are typically composed of resistors and capacitors and can effectively isolate signals or energy in a circuit.
Working principle of resistor
1. Basic Principles
A resistor is a passive component that limits the flow of electric current and converts electrical energy into heat or other forms of energy. The working principle of a resistor is based on the movement of free electrons within a material. As these free electrons move through the material, they collide with atoms or molecules, resulting in energy dissipation. The resistance value is determined by factors such as the material, length, and cross-sectional area.
2. Principles of Materials
The atomic structure of a resistive material affects its resistance value. Generally speaking, metals have high conductivity because their atomic structure contains free electrons that can move freely and are not affected by electric fields; while non-metals have relatively poor conductivity because their atomic structure lacks free electrons.
3. Calculation Principle
The working principle of a resistor is based on Ohm's law, which states that the relationship between current (I) and voltage (V) is linear, i.e., I = V/R, where R is the resistance value. The resistance value of a resistor is determined by the material, cross-sectional area, and length of the resistive element.
A braking resistor, also known as a dynamic braking resistor, primarily dissipates the kinetic energy of the braked mechanical system through a power resistor to brake the system. Why are braking resistors present in some servo motor drivers? Are braking resistors also needed in the motor drives of intelligent car models?
Braking resistors, also known as dynamic braking resistors, are mainly used to dissipate the mechanical kinetic energy of the mechanical system being braked through a power resistor in order to brake the mechanical system.
When a motor-driven mechanical system is braking, the motor transforms into a generator, converting the braking torque into electrical energy. If the motor's drive system lacks an inverter function (i.e., to convert the electricity back into primary energy and feed it back to the grid or battery), then the braking energy can only be dissipated through a power resistor. Otherwise, this energy has nowhere to go, leading to overvoltage and overcurrent within the drive circuit, potentially damaging the circuitry.
Essentially, when a small model car decelerates and brakes, its kinetic energy needs to be dissipated before it can stop.
The ways in which the kinetic energy of the model car is consumed include: the frictional resistance between the model tires and the ground, the transmission resistance from the model car motor to the wheels, the mechanical energy absorbed by the motor being converted into electrical energy and consumed in the drive circuit, and the conversion into electrical energy being recharged into the vehicle battery.
A mass block is added to the wheel of a model car to simulate the inertial mass of the entire vehicle during operation. The wheel rotation speed can be measured using an optical encoder on the gear. The following experiment will show the situation when the wheel decelerates.
The simplest way to decelerate a model car is to stop applying drive voltage to the motor. This means disconnecting the motor from the drive circuit. If the motor drive module has an enable pin, setting it to the closed state will cause the drive module's output port to exhibit high impedance, effectively disconnecting the motor from the circuit.
The mechanical kinetic energy of the model car can only be dissipated through friction with the ground and the resistance of the transmission system. Generally, frictional resistance is constant and independent of speed, so the wheel deceleration is a constant value. The car speed decreases linearly.
I. The concept of driver resistor
A driver resistor is a component used to drive a motor, typically installed between the motor's output port and the driver. The primary function of a driver resistor is to regulate the motor's drive current. When the motor load is light, the resistor is used to limit the current to protect the motor; conversely, when the motor load is heavy, the resistance needs to be reduced to increase the motor's output power.
II. The function of the driver resistor
1. Controlling motor torque
The driver resistor can control the motor's output torque by adjusting the motor's drive current. When the motor needs to generate high torque, the driver resistor reduces the current, thereby reducing the voltage across the motor, which in turn reduces the motor speed and increases torque.
2. Protect the motor
Driver resistors prevent motor overload and overheating. When a motor encounters an excessive load, the driver resistor limits the current to protect it from damage. Simultaneously, the driver resistor can also limit the current by increasing the motor's resistance, preventing the motor from overheating.
3. Improve motor operating efficiency
A driver resistor can reduce the motor's power loss and improve its operating efficiency by decreasing the drive current. When the motor's load decreases, the driver resistor reduces its resistance, thereby increasing the motor's output power.
III. Summary
Driver resistors are essential components in motor drive circuits. They control the motor torque by adjusting the drive current, protect the motor from damage, and improve its operating efficiency. Therefore, in motor control systems, correctly selecting and properly adjusting driver resistors can ensure the normal operation of the motor and extend its lifespan.
