pwm pulse width modulation tutorials

There are a number of occasions where you might need Pulse Width Modulation for regulating power to a number of devices .It could be your Motor or even a lighting device .Let me explain
PWM first .

It is the variation of duty cycle from 0 to 100 % .To put it in a smiple way

"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."

The following picture will give you a clear idea about it



It shows three different PWM's of 10% , 50% and 90% .
Notice: 100 % would become constant DC .

For instance take 10% duty cycle .You switch on the power for 10% of the time and switch it off for the remaining 90 % of the time .

Let me give you a practical example .Take a wave of frequency 1KHZ =1000 HZ .The time period of one wave as you know is 1millisecond .So a wave of 10% duty cycle will remain switched on for .1 millisecond
50% for .5 ms and so on .

You could achieve PWM by simple circuits like using a 555 timer .But the best part is you have built in pwm modules in PIC16f877A .Using which you can modulate the wave .For applications like motor control you can acheive smooth acceleration using these pwm modules present in the PIC .I will tell you about the coding and pic specifics in the next post .

next Tutorial -->

Robonics - My Robotics Start Up

Heyy People
It has been a while since I wrote something here. I have been busy all these days.. Busy with what ???? ..
Well I have been working hard to launch my own company. What does the company deal with ?
What other than robotics (my passion). Presently I am have developed and manufactured some development board, programmers and a few mechanical parts. I hope to extend my catalog to lots of other parts.

Company Name
I have named my company ROBONICS.
etymology: Robo from Robotics and nics from electronics constitute ROBONICS.This name was suggested by my friend gopi.. I liked it and so named it.Some of my friends accused me for the name not being jazzy ... I should have added an X or Z. Well I like to keep it clean and simple .. I am happy with this name.

Why I started this company ?

• One major reason being there arent any robotics company in Chennai , Hyd , Cochin that manufactures and sells kits. Of course there are many players in North India.
• Second reason being, all the kits that you get online are costly which are sold at a huge margin.So I wanted to provide kits for students that is cheap as well as easy to use .(Budget is always a problem for we robotists)
  

Wish me good luck for my business to succeed guys and gals .. For I need you to for this business to succeed.

Shop
There is an online shopping cart that you can use to shop for products. Some of the very useful products that I would like to recommend is

• PIC Development Board.
• Multi PIC Programmer

Please do check out the website guys ..and wish me luck again.

PCB designing Video Tutorial and Ebooks

Easy to use PCB designing Tutorial

PCB designing is no more a hard core designer’s job , even cons like us can design the PCB using this brilliant software “PCB WIZARD”. You need not be a wizard when you Have PCB wizard in hand.

Unlike most of the PCB designing software’s PCB WIZARD is very user friendly.
(I am telling this keeping in mind that I‘ve tried many other designing software’s).
.The coolest thing that I found in this software is you don’t have to design the PCB at all. It makes PCB for you. How cool is that?

You’ve to just draw the circuit (schematic diagram)



then select the option convert
“Design to Printed circuit board”



The software makes the PCB for you .This is done by auto routing .They even provide manual design mode for advanced users.


Autorouting in action watch the video .



No more you have to be a master knowing each and every spec of the electronic components the pins diameter the size of drill bit .Nothing nothing this software does it for you.


COMPONENT LIBRARY

But there are a few draw backs as well .When you choose the automatic conversion option It lets you down on the aesthetics part .But I don’t mind as far as it is done at the hobby level and if I can design PCB so easily why care about aesthetics.
And the component library is also not adequate .Especially L298 is missing .It also lacks SMD library.

They even have tutorials about etching PCB‘s .And more importantly they don’t have restriction on the size of the PCB.

Download it from here
If you are looking for Ebooks about designing here is the link .


Ebook-Tutorial-1
Ebook-Tutorial-2
Ebook-Tutorial-3
Ebook-Tutorial-4

Final designed PCB

You can select different view modes like prototype,solderside layout ,component side layout and silk screen layout .If you want to design a PCB to replace all your annoying soldered circuits boards which gives you head ache "PCB WIZARD " is the software for you .

How to build a sumo robot ?

How to build a sumo robot ?
Sumo wrestling is an interesting and thrilling event and it has a history and tradition behind it.Basically it may be held as an autonomous or wireless controlled event.So lets see the basics of building a SUMO robot.
CHOOSING A MOTOR
First deceide the motor you are going to use.Speed is inversely proportional to torque.So go for a slow speed motor that gives good torque.And then start building the chassis click here ---> > for more mechanical designs and ideas.
STEERING MECHANISM
Then build your chassis .And deceide the steering mechanism that you are going to use.Always go for differential steering than ackerman steering mechanism.Differential steering provides more manuverablity and easy control which is crucial.Incase you dont know what differential steering mechanism is I will explain you with the following diagram .



I'll explain you the steering mechanism

Both motors forward bot moves forward . If left motor is switched off or reversed bot and right motor is forwarded turns towards left ..and the other way for the right turn.This is very basic and most people know it.
INTERFACING RADIO CONTROL
Then you have to choose a radio control kit.it is always better to have two kits to avoid frequency interference.You can use RC kits stripped from old cars .Then you will have to use the signal from the receiver and drive your motors.If your are using big motors do not use the receicer to drive the motor directly .you might fry it.So you have to make a driver to drive the motor.A H bridge is usually used to drive the motor, relays can also be used.If you use relays you need not worry about voltage and current ratings of motor.
VERY VERSATILE H BRIDGE


Click on the image to see clearly .

This is a very versatile H bridge circuit.And D88O is a power transistor having a max current range of 3 A and voltage range more than 50 v and more amazing is is that it costs only 4 rupees in my backyard.So what happens is when D1 and D3 are switched on motor runs in forward direction and when D2 and D0 is switched on motor reverses its direction.
TIP
If you look at the RC kit you will find 4 controls forward ,reverse,left and right.So the easiest way to drive the robot is use the forward and reverse channel to control one and left and right to control another.Of course can make better controls by decoding the output but this is the easy way.
LOOKS CRAPPY BUT DAMN EASY!!!!


click on the image to see clearly .
RELAY BASIC IDEA
This is the circuit to drive the motors using relays.A relay has 5 pins 2 for the energising coil and 3 for contacts .There is one movable contact and two fixed contacts .And the movable contact is in contact with a default pin when the relay is not switched on .For more tutorials on how relay works> click here .
HOW THE ABOVE CIRCUIT WORKS
So here when when one transistor is switched on the movable contact moves and comes in contact with the +ve supply and since the other end is grounded the motor runs in one direction .And the viceversa happens when the direction is reversed .(Those protection diode is not needed this transistor can withstand much abuse)
AND AT LAST PS
PS:THIS CIRCUIT MAY LOOK COMPLICATED BUT ITS VERY EASY I'VE USED THIS CIRCUIT A LOT OF TIMES .YOU CAN USE 12 V OR 6 V SUPPLY.AND YOU CAN EVEN USE A 6 V RELAY IN CASE YOU ARE USING 12 V SUPPLY(its so versatile), AND NOTHING HAPPENS WHEN 6 V RELAY IS CONNECTED TO 12 V SUPPLY (thanks to back emf)...