Super Mario

I want to build my first line following robot.
I ordered my first PIC and programmer, and I got tutorials which were really good for my level , and I have some electronics knowledge.

Now I need to know about motors , can anyone explain to me in breif how exactly the motors will work in mechanical point of view , for example,how many motors I will need and how to make the robot move right and left..etc , and should I start learning about motors starting from the basics or is it okay to start with a specefic type ( i hear ppl talking about stepper motors)?

Thanks

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andy257

Hi there,

sorry to hijack your post but could i ask where you got information on programming PIC. I wish to learn how to do this also.

cheers

andy

pike

In response to andy: Head over to www.winpicprog.co.uk from there you can find tutorials on learning how to program PICs.

Servo motors are motors that have steps inside them, that means you have to pulse electricity to the motor at different wires. This allows you to control the position of the shaft very acurately.

say i have a servo motor with 60 steps: 360 degrees/60 steps = 6 degrees in motion per step. To make to motor run a full revolution i need to pulse 60 times to the motor.

The only thing that i see servos can do in a car is control the steering mechanisms. everything else can be powered by a normal DC motor.

you could use the skid-steering method of steering, which is much easier. Military tanks use this form of steering because it allows a lot of traction.

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Super Mario

Thanks for the info pike!

Andy here's a site I found that I think it's good for absolute beginners (like me)

http://www.mstracey.btinternet.co.uk...al/picmain.htm

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falleafd

pike,

you got mistakes, the servo motors have two typical types which are DC servo and AC servo.

A DC motor is the most popular motor in robotic applications. Servo mechanic structure is just a DC motor and an encoder fixed together.

Servo motor is a close loop motor. You need to use PWM to drive a servo. you may use some chips like: TA7288A, L293, L293D, L298, ...


The motor you say is a Stepping (Step or Stepper) motor. Stepping is a open loop motor, the smallest full step is 0.72 deg/step. However, you may drive it at half step mode, or microstep mode to make it nearly continously run. The suitable chips for stepping may be ULN2003A, ULN2803....

http://www.cs.uiowa.edu/~jones/step

mario,

But normally, for beginner, you should try with simple DC motors.

To drive a small robot, there are many model of wheeled mobile robots. However, you can use NEWT model, which is easy to drive the robot, with 2 active wheels. Active wheels, that is, the wheels are connected to motors. An the 2 wheels are on opposite sides.

At first, you should solve the kinetics, and understand how to drive a robot. There are many simple robot projects, especially on linefollowing. However, my data was lost, and I don't remember the usefull URLs. But you may check in this forum, people discussed much bout it.

You can firstly build a line follower with basic PIC 16F84, it's very easy, and you can build your own IR sensor to detect the line. You need only 2 pins of PIC to detect IR sensor. Try it, and good luck.

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pike

my mistake....sorry.

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ivancho

There are some simple fact that you need to know about motors.... There are 3 basic types of motors:
-Simple DC Motors
-Stepper Motors
-Servo Motors.

You sould research those, "simple" DC motors will run at high RPMS... that means that you are going to need to lower those RPMS to gain some torque. Torque is the force need to move somthing. So a DC motor will need some gearhead to lower the RPMS and increase the torque.... but how much torque you need depends on how heavy it is that you are trying to move. This motors have 2 wires where you connect power to, and depending on the polarity the motor moves in certain direction.

Stepper motors like mention before are motors that rotate in steps. They normally have 4 wires and can be either bi-direcetional or unipolar. Stepper motors are more difficult to "drive" out of all of the motors, mostly because it need precise stepping frequency. They also need to be ramped to speed, and the faster they go the less torque they have, and the slower they go the more torque they have.

Servo motors are DC "geared" motors with a feedback and electronics included..... These motors have 3 wires: 2 for power and a signal wire that will move the servo one direction or the other depending on the pulse width you send. The way this motors work is they move a potentiometer, each time they rotate, the electronics inside read the value of the potentiometer and see if the motor is located at the position where the siganl is commanding it to go. The siganl you send to the stepper is between 1ms and 2ms... 1.5msec being in the dead center. (Research on servo motor to make sure you understand what I mean)

Servo motors are the easiest to use, if you where to modify it for continous rotation. For U$13 you have a DC gearhad motor with some known torque and the electronics needed to drive them, all in a compact packet. And the control of thise motors is by far the quickest and simplest of all.

To turn a 'bot all you do is drive a wheel faster than the other one. The robot will tunr toward the wheel that is moving slower. IF you where to have one wheel stopped and the other running you will accomplish a 360 degree turn. That is the easies way to make a robot turn. Most of the robots will have 3 wheels one caster and the other two motorized.

Good luck

Ivancho

mr.engineering

i read all the thread...and i got that to build an easy moving robot,easy in rotating also,use servo motors is the best,right?

i have a question to ask.....do i need a motor for each wheel


if i have a 4 wheeled robot or 2 wheels,do i need a motor for each,or i can control both by one motor


thanks in advance


really great thread,i got alot out of it

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ElectronikCid122

well lets say u have 2 motor s. one which will make it got forward and backwards and 1 which will make it go left and right. now to make them go forwards backwards left right the polarities of the motors switch. and im pretty sure thts done by a speed controller servos or maybe even a relay

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pops

Any way... how to control two motors ie varying their speed to turn left or right, opposite direction to circulating along it self...

Please give me full depth... am a NEW one...

Thanks...

Sceadwian

The most common method to control the speed of a DC motor (like RC car motors) is using an H-bridge, it's basically 4 transistors or Mosfets in an h configuration that allow controlling which leads are connected to the power or ground lines. There have been exaustive posts in the forums here and Wikipedia should have some information about them but I'm not sure as I can't access it right now. Any Google for h-bridge will give you everything from basic theory to advanced circuits.

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dknguyen

Best tutorial I've found on H-bridges so far:

http://www.modularcircuits.com/h-bridge_secrets1.htm

Has good diagrams and goes over the basics as well as other "little" side issues like flyback diodes, and high side. It also goes over the different kind of switching methods available.

William At MyBlueRoom

I like the Tamiya gearboxes, not too hard to find and about the price of a single servo motor. The Dual Gearbox pictured below is what I'm using in my upcoming robot chassis (Mongoose)

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rikaldrey

@ William At MyBlueRoom

Where did you get your tamiya gearbox? Do I need to buy a certain tamiya toy to get that gearbox or I can buy the gearbox only? Please guide me as I am a noob also.

One more thing, where can I fine servo motors? can I buy them also? Do I need an h bridge to drive a servo motor? Thanks in advance.

blueroomelectronics

I've found the gearboxes available at many hobby stores.

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