PWM-Speed-Motor | Electronic Project Circuits

Posts Tagged ‘PWM-Speed-Motor’

A Simple PWM Circuit Based on the 555 Timer

One of the most fundamental problems in robotics is DC motor speed control. The most common method of speed control is PWM or pulse width modulation. Pulse width modulation is the process of switching the power to a device on and off at a given frequency, with varying on and off times. These on and off times are referred to as “duty cycle”. The diagram below shows the waveforms of 10%, 50%, and 90% duty cycle signals.

When the circuit powers up, the trigger pin is LOW as capacitor C1 is discharged. This begins the oscillator cycle, causing the output to go HIGH.

When the output goes HIGH, capacitor C1 begins to charge through the right side of R1 and diode D2. When the voltage on C1 reaches 2/3 of +V, the threshold (pin 6) is activated, which in turn causes the output (pin 3), and discharge (pin 7) to go LOW.

When the output (pin 3) goes LOW, capacitor C1 starts to discharge through the left side of R1 and D1. When the voltage on C1 falls below 1/3 of +V, the output (pin 3) and discharge (pin 7) pins go HIGH, and the cycle repeats.

Pin 5 is not used for an external voltage input, so it is bypassed to ground with an 0.01uF capacitor.

Note the configuration of R1, D1, and D2. Capacitor C1 charges through one side of R1 and discharges through the other side. The sum of the charge and discharge resistance is always the same, therefore the wavelength of the output signal is constant. Only the duty cycle varies with R1.

The overall frequency of the PWM signal in this circuit is determined by the values of R1 and C1. In the schematic above, this has been set to 144 Hz.

Read More Source: http://www.dprg.org/tutorials/2005-11a/index.html
Thank you.

Be the first to comment - What do you think? Posted by admin - November 15, 2007 at 9:14 am

Categories: Motor controller Tags: 555 pwm circuit, motor control, PWM-Speed-Motor

Three channel fan speed controller for PC

Three channel fan speed controller for PC

Jos van Eijndhoven have designed a 3 channel fan motor controllerbased on PIC 16F676 microcontroller. Mcu reads temperature from sensors and outputs PWM modulated signal to each output so the speed of fan is controlled accordignly. Three on board potentiometers controls the start up temperature for each channel. The speed of fan is controlled linearly according to temperature and drops slowly when temperature goes down fast to avoid instability. For the output transistors BUZ72 are selected and temperature sensor is LM60. PIC code is written in C and compiled to hex using free CC5x compiler.

Read More Source:http://jos.vaneijndhoven.net/fancntl/index.html
Thank you.

Be the first to comment - What do you think? Posted by admin - October 2, 2007 at 2:48 pm

Categories: Circuit com, Electronic Control Tags: Motor controller, pc fan speed control, PWM-Speed-Motor

How to make an H-bridge

An H-bridge is a type of circuit that you can use to get a reversible DC motor to spin both clockwise and counterclockwise.

In other words, this circuit allows you to quickly reverse the direction a motor is spinning by using a switch or controller chip to change its direction.

I’m going to show you how to make the simplest and most reliable form of H-bridge that I know how to make. I must warn you that this is by no means the best H-bridge design and, in fact, it has a couple shortcoming which I will explain later.

Although, should you never have made an H-bridge before or simply need a circuit that can reverse the direction of a motor’s spin, then this circuit is a quick and easy solution.