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LM324 Application: DC Speed Regulation System Circuit [FAQ]

  • Contents

I. Description

 

The LM324 integrated quad operational amplifier has the characteristics of wide power supply voltage range and low static power consumption, so it is widely used in various circuits. This article describes the application circuits of different functions formed by LM324 in the regulation circuit of the DC speed regulation system: zero blockade circuit, given integrator circuit, adder and limiter circuit. By calculating and analyzing the working principle of these unit circuits, their roles in the system and the key point voltages, the core role of the LM324 integrated four-ops in the regulating circuit is explained.

LM324LM324

Catalog

I. Description

II. LM324 Integrated Operational Amplifier

2.1 LM324 Pin Functions

2.2 LM324 Features

III.Overview of DC Motors

IV. Principles of DC Speed Regulation System Circuit

V. LM324 Application Circuit Analysis

5.1 Zero Blockade Circuit

5.2 Given Integrator Circuit

5.3 Voltage Comparison Circuit

5.4 Adder and Limiter Circuit

VI. Conclusion

FAQ

Ordering & Quantity


II. LM324 Integrated Operational Amplifier

2.1 LM324 Pin Functions

 

There are 4 operational amplifiers inside LM324, it has phase compensation circuit, working voltage range is wide, it can work with positive power supply 3~30 V, or positive and negative dual power supply ±1.5~±15 V. It's input voltage can be as low as ground potential, and the output voltage range is 0~VCC. The LM324 circuit symbol is shown in Figure 1. It has 5 lead pins, among which "+" and "-" are two signal input terminals, and "V+" and "V-" are positive and negative power terminals. "Vo" is the output terminal. Figure 2 shows the pin layout of LM324, and Table 1 shows the main parameters of LM324.

Figure1 LM324 circuit symbol

Figure1 LM324 circuit symbol

Figure 2 LM324 Pinout

Figure 2 LM324 Pinout

Table 1 LM324 Main Parameter

Table 1 LM324 Main Parameter

 

2.2 LM324 Features

 

(1) Wide operating voltage range of single power supply or dual power supply; single power supply 3V~32V, dual power supply ±1.5V~±15V

 

(2) Built-in phase correction circuit,  few external components

 

(3) High gain frequency compensation calculation

 

(4) Rated power supply voltage: +15V

 

(5) Short circuit protection output

 

(6) True differential input stage

 

(7) Low bias current: 100nA max

 

(8) Each package contains four operational amplifiers

 

(9) Has the function of internal compensation

 

(10) Common mode range extended to the negative power supply

 

(11) Industry standard pinout

 

(12) The input terminal has an electrostatic protection function

 

III.Overview of DC Motors

 

The DC motor uses a thyristor rectifier to rectify the alternating current into an adjustable direct current and introduces voltage negative feedback, current cut-off negative feedback, etc. to form an automatic speed stabilization step-less speed regulation system. In order to make the equipment work at a reasonable speed during the production process, most manufacturers need to use a speed-adjustable DC motor. The DC motor speed control system composed of integrated operational amplifier circuit LM324 is applied in the production occasions of DC speed control, with stable performance and can achieve the purpose of improving product quality.

 

IV. Principles of DC Speed Regulation System Circuit

 

The regulation circuit is the core of the speed regulation control circuit. The circuit is mainly composed of a zero blockade circuit, a given integral circuit, a filter type regulation circuit and a protection circuit. Its main function is to synthesize, adjust and amplify the voltage of the given signal, the current cut-off negative feedback signal, voltage negative feedback signal, phase loss signal and overcurrent signal, and the generated output voltage is used as the control of the integrated phase shift pulse trigger Voltage. By controlling the trigger pulse angle (phase shift angle), the output voltage of the thyristor rectification system is controlled.

 

V. LM324 Application Circuit Analysis

 

LM324 can be composed of the proportional amplifier circuit, proportional integral circuit, adder circuit and so on. Below we will analyze the specific application circuit of LM324 in the DC speed regulation circuit.

 

5.1 Zero Blockade Circuit

 

The function of the zero blockade circuit is to prevent the motor from crawling due to factors such as temperature drift of the components in the control circuit. The basic circuit is shown in Figure 3.

Figure 3 Zero blockade circuit

Figure 3 Zero blockade circuit

 

Since the feedback resistance R5=2 MΩ, the zero blockade circuit is similar to a voltage comparator. When UB=+15 V,

 

 

That is, the non-inverting input of the operational amplifier is 0.29V, and the inverting input is Ug'. The range of Ug' is -9.7~9.7V.

 

When Ug'<UA, that is, Ug'<0.294V, UB=+15V, diode VD3 turns on, UO1=14.7V.

 

When Ug'>UA, that is, Ug'>0.294V, UB=+15V, diode VD3 is off, UO1=0V.

 

5.2 Given Integrator Circuit

 

The function of the given integrator circuit is to change the abrupt signal into a continuous and slowly changing signal to prevent the sudden addition of the given signal from causing the output voltage to rise, causing the motor to overcurrent. The basic circuit is shown in Figure 4.

 

Figure 4 Given integrator circuit

Figure 4 Given integrator circuit

 

The given integrator circuit is composed of voltage comparison circuit Ug', C5 integrator circuit and a feedback circuit. The given voltage is filtered, and then after the anti-interference correction network composed of R10, R11, and C6 without delay, it acts on the buffer composed of IC1B, R11, Rp6 for buffering. Adjusting Rp6 can change the integral constant (integration time), and then output through the integrator composed of IC1D, C7, C8, etc. and finally output the C02 voltage through the calibration network again.

 

When Ug'≤0, UA=-15V. Due to the function of diode VD6, U02=UUg'+0.7V, and the adjustment range is -9.7~+9.7V.

 

When Ug'≥0, UA=+15V. Due to the feedback resistor R18, U02=Ug', and the adjustment range is -10V to 0V.

5.3 Voltage Comparison Circuit

 

The basic circuit is shown in Figure 5.

Figure 5 Voltage comparison circuit

Figure 5 Voltage comparison circuit

 

This circuit is a hysteresis voltage comparator, input signal Ub3=Ub1+Ub2.

 

 

When Ub3<-0.29V, UB=+15V, Ub4=14.3V, when Ub3>-0.29 V, UB=-15V, Ub4=0V. The function of the hysteresis loop is anti-interference, and the loop width of the sub-circuit is only about 0.6V.

 

5.4 Adder and Limiter Circuit

 

(1) The role of the adder: the role of the filter regulator is to output voltage U01 to the zero-blocking circuit, output U02 to the given integrator circuit, output voltage U03 to the voltage negative feedback circuit and current cut-off negative feedback circuit, and amplify the integrated voltage Uk of the output voltage U04 of the protection circuit to obtain the control voltage Uk to control the control angle of the trigger pulse, thereby controlling the output voltage of the thyristor DC drive device. The adder and limiter circuit is shown in Figure 6.

 

Figure 6 Adder and limiter circuit

Figure 6 Adder and limiter circuit

 

(2) Analysis of the working principle of the adder: The circuit is an adder composed of an integrated operational amplifier and a non-polar capacitor composed of capacitors C9 and C10 in reverse series, which plays a filtering role in the circuit. The control voltage is:

 

The function of the limiting circuit is to limit the maximum output value of the UK voltage by adjusting the potentiometer Rp1, and adjusting the potentiometer Rp2 can limit the minimum negative output value of the UK voltage. Adjusting reasonable positive and negative limiting voltages can control the minimum control angle αmin and the minimum inverter angle βmin.

 

 

VI. Conclusion

 

The four-op-amp LM324 integrated circuit is used with resistors and capacitors to achieve various functions in a certain circuit connection. The four-op-amp LM324 integrated circuit plays a core role in the entire circuit. In the circuit operation, when the given voltage is less than 0.3 V, the thyristor DC drive device has no output voltage. When the given voltage is greater than 0.3 V, the thyristor DC drive device can drive the DC motor with a normal output voltage to achieve the purpose of driving the motor speed.


FAQ

  • What is lm324?

LM324 is a Quad op-amp IC integrated with four op-amps powered by a common power supply. The differential input voltage range can be equal to that of the power supply voltage. ... Generally, op-amps can perform mathematical operations.

  • Which is the difference between lm324 and lm339?

The LM324 has a complementary output while the LM339 is open collector. In the complementary output, current can flow in either direction as required (either source or sink) while the open collector output can only sink current.

  • What is op-amp used for?

Operational amplifiers are linear devices that have all the properties required for nearly ideal DC amplification and are therefore used extensively in signal conditioning, filtering or to perform mathematical operations such as add, subtract, integration and differentiation.

  • How does an op-amp work?

  • What is lm324 used for?

LM324 IC Applications

The applications of IC LM324 include the following. By using this IC, conventional op-amp applications can be implemented very simply. This IC can be used as oscillators, rectifiers, amplifiers, comparators etc.

  • What is the function of a temperature controller?

A Temperature Controller is a device that is used to control a heater or other equipment by comparing a sensor signal with a set point and performing calculations according to the deviation between those values.

 

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