Electronic Circuits and Diagram-Electronics Projects and Design

DC motor control circuit using NE555 Description. A simple DC motor controller circuit using NE555 is shown here. Many DC motor speed control circuits have been published here but this is the first one using NE555 timer IC. In addition to controlling the motors speed its direction of rotation can be also changed using this circuit. A PWM circuit based on timer NE555 is the heart of this circuit. NE555 is wired as an astable multivibrator whose duty cycle can be adjusted by varying the POT R1. The output of IC1 is coupled to the base of transistor Q1 which…

H Bridge Motor Control Given below is an H bridge motor control and  driver circuit using IC L298 Description : A bidirectional H bridge DC motor control circuit is shown here. The circuit is based on the IC L298 from ST Microelectronics. L298 is a dual full bridge driver that has a wide operating voltage range and can handle load currents up to 3A. The IC also features low saturation voltage and over temperature protection. In the circuit diode D1 to D4 are protection diodes. Capacitor C2 is the logic power supply filter and capacitor C2 is the supply voltage filter….

Description. The circuit shown below is of a DC motor driver circuit based on the IC TC4424 from Microchip. TC 4424 is a dual MOSFET driver that can be used in a variety of applications like SMPS, pulse transformer drivers, line drivers, motor drivers etc. The speed and of direction rotation of the motor depends on the logic levels of pin 2 and 4. The speed of rotation of the motor is proportional to the duty cycle of the PWM signal fed to pin 2. If the pin 4 is held at logic 0 the motor will run in the…

Description. The circuit given here is of a simple H bridge motor driver circuit using easily available components. H Bridge is a very effective method for driving motors and it finds a lot of applications in many electronic projects especially in robotics. The circuit shown here is a typical four transistor H Bridge. The diodes D1 to D4 provide a safer path for the back emf from the motor to dissipate and thus it protects the corresponding bipolar transistors from damage. Resistors R1 to R4 limit the base current of the corresponding transistors. Working of this circuit is very easy…

Description. Many electronic circuits related to fan speed controlling have been published here and this one is just another approach. The circuit diagram shown here is of 12V DC fan speed controller using the IC LM2941CT which is a low drop out 1A voltage regulator. The IC has a dropout voltage as low as 0.5 and has also many useful features like power supply reverse protection, thermal protection, short circuit protection etc. The maximum output current the IC can source is 1A. The 12V DC supply is connected between the Vin (pin4) and ground (pin3) of the IC. The load,…

Description. The schematic of an automatic cooler fan for audio amplifiers is given here. The circuit automatically switch ON the cooler fan whenever the temperature of the heat sink exceeds a preset level. This circuit will save a lot of energy because the cooler fan will be OFF when the amplifier is running on low volume. At low volume less heat will be dissipated and it will not trigger the cooler fan ON. The temperature is sensed using an NTC (negative temperature coefficient) thermistor R2. Junction of thermistor r2 and resistor R1 is connected to the inverting input (pin3) of…

Description. Here is the circuit diagram of a low voltage /low power DC motor speed controller based on the IC TDA 7274 from ST Microelectronics. The IC TDA 7274 is a monolithic integrated DC motor speed controller intended for low voltage/ low power applications. Built in internal voltage reference voltage, wide input voltage range (1.8 t0 6V), high linearity, 700mA output current, excellent temperature stability etc make this IC well suitable for almost all low power DC motor speed control applications. The motor to be controlled is connected between pin3 (Vs) and pin4 (output) of the IC. Resistor network comprising…

Description. Here is a simple circuit for controlling the speed of DC operated PCB drills. The heart of this circuit is the ICLM3578 which is a very efficient integrated switching regulator that can be used for applications like this. The LM3578 has separate inverting and non inverting feedback inputs (pin1 and pin2), 1V internal reference voltage source and a built in oscillator circuit. The IC can be configured to obtain up to 90% duty cycle. In the circuit, capacitor C2 is the timing capacitor which determines the frequency of the internal oscillator. The duty cycle depends on the sum of…

Description. The circuit diagram given here is of a stepper motor driver using MC3479 from Motorola. The MC3479 is specifically designed for driving a 2 phase stepper motor in bipolar mode and is available in standard DIP and surface mount packages.The IC is compatible to TTL and CMOS inputs and has selectable HIGH/LOW output impedance. The output can deliver up to 350mA each of two coils of a 2 phase stepper motor. The state change of the output occurs at the low to high transition of the input clock pulse. The new output will depend on old output and the…

Description. This circuit is designed as per a request made by Mr Vinoth from India. His requirement was a 12V/5A DC fan motor controller. I think this circuit is sufficient for this purpose. Quad 2 input Schmitt trigger IC CD4093 is the heart of this circuit. Out of the four Schmitt triggers inside the 4093, U1a is wired as an oscillator with adjustable duty cycle. The U1b, U1c, U1d buffers the output of the oscillator to drive the switching MOSFET Q1.The MOSFET drives the DC motor according to the switching pulse obtained from the oscillator. When R1 is varied the…