help with motors

[vishu412k]

can anybody tell me how to get more:
1.power Or
2.speed

out of a simple moter, ie , if its possible. i need to use the same robot for speed racing and then robotwars. for racing i'll need max possible speed, and for the wars....max possible power. is it possible to use the same motors.
in fact i would appreciate if someone could explain what power output of a motor depends on.

also, i need a little help in modifiying my robot. i need a new turning mechanism. i'm using differential spin between the motors to turn. can someone point a better method where i can CONTROL THE AMOUNT THAT MY ROBOT TURNS, RATHER THAN TURNING 90 DEGREES ALL THE TIME (eg. electromagnet, but again i can't seem to figure out how to control the amount i turn...like using a pot in place of a steering wheel :wink: .....).

 

[Nigel Goodwin]

can anybody tell me how to get more:
1.power Or
2.speed

out of a simple moter, ie , if its possible. i need to use the same robot for speed racing and then robotwars. for racing i'll need max possible speed, and for the wars....max possible power. is it possible to use the same motors.
in fact i would appreciate if someone could explain what power output of a motor depends on.

Increasing the voltage to the motor (which also increases the current) will provide higher speed and more power. It's common practice to run 12V motors at 24V, or even 36V, to increase power substantially, relying on the short term use to avoid burning the motors out. To increase the power ONLY, you would need to lower the gear ratio from motor to drive.

also, i need a little help in modifiying my robot. i need a new turning mechanism. i'm using differential spin between the motors to turn. can someone point a better method where i can CONTROL THE AMOUNT THAT MY ROBOT TURNS, RATHER THAN TURNING 90 DEGREES ALL THE TIME (eg. electromagnet, but again i can't seem to figure out how to control the amount i turn...like using a pot in place of a steering wheel :wink: .....).

I don't really understand what you are currently doing?, usually you have two motors, one driving the left wheels and the other driving the right wheels. If you slow down the left motor it turns left, if you slow down the right motor it turns right - depending how much you slow the motor, and how long for, sets how far it turns.

 

[vishu412k]

usually you have two motors, one driving the left wheels and the other driving the right wheels. If you slow down the left motor it turns left, if you slow down the right motor it turns right - depending how much you slow the motor, and how long for, sets how far it turns.

this is what i'm doing now, but the problem is.....
1.how do i slow the motor. currntly i'm stopping it completely while the other runs at full speed. this means each time i turn, the car turns s full 90

2.turning motion is quite jerky. controlling it is difficult.

i was hoping to use a solenoid and vary the currnt to it (using a pot), so that the magnet moves slightly if i increase the current only slightly....and so on,.....then i could somehow hook it up to an axle(i'll figure that out later :wink: ). problem is i've never used a solenoid before. i dont even know if this kind a mechanism is possible.

 

[Nigel Goodwin]

this is what i'm doing now, but the problem is.....
1.how do i slow the motor. currntly i'm stopping it completely while the other runs at full speed. this means each time i turn, the car turns s full 90

How far it turns depends on how long you stop the motor, it sounds like your control system is very primative? - even a simple toggle switch could make a pretty short break of power.

2.turning motion is quite jerky. controlling it is difficult.

i was hoping to use a solenoid and vary the currnt to it (using a pot), so that the magnet moves slightly if i increase the current only slightly....and so on,.....then i could somehow hook it up to an axle(i'll figure that out later :wink: ). problem is i've never used a solenoid before. i dont even know if this kind a mechanism is possible.

The way to do it is called PWM - don't mess about with solenoids and pots, it's not going to work like that!. There is lots of information about PWM all over the internet, a search will find you plenty of help.

 

[mayanktrehan]

First of all ,if ur in India which by looking at ur name i suppose so, whatever competitions u intend to go for do take into consideration the fact that 90% of the robots competing are going to only turn 90 degrees.
The only robot that i've heard does really cool stuff is the one built by D.P.S RK Puram in Delhi which has been winning the IIt tech fest for the past few years now .(but i have never had a chance to see their robot so i cannot comment ) So why take the the drastic step of changing the entire principle on which your robot works? Better still include better technology in a new robot and take both to the competitions and your chances of winning it will increase!
:wink:

 

[mayanktrehan]

First of all ,if ur in India which by looking at ur name i suppose so, whatever competitions u intend to go for do take into consideration the fact that 90% of the robots competing are going to only turn 90 degrees.
The only robot that i've heard does really cool stuff is the one built by D.P.S RK Puram in Delhi which has been winning the IIt tech fest for the past few years now .(but i have never had a chance to see their robot so i cannot comment ) So why take the the drastic step of changing the entire principle on which your robot works? Better still include better technology in a new robot and take both to the competitions and your chances of winning it will increase!
:wink:

 

[bmcculla]

I'd use a "drive by wire" sort of system. You should use H-bridges to drive each motor. This lets you drive the motor forward and backward and vary th power. You should also build a optical encoder fro each wheel so you can tell how fast its going.

About the drive by wire system. Rather than have your control inputs go strait to the motors you should have them go to a microcontroller. The microcontroller can figure out what you want to do and more precicely control the motors to do what you want. So instead of doing things like "right motor on" you could tell the microcontroller to turn the robot 30 degrees and the microcontroller controls the motors to make that happen. This would let you design a much more intuitive and easy to use control system for your robot.

 

[electronist]

I totall agree with nigel, instead of changing the hardware it would be better to change the software and go for pulse width modulation. This will help you in achieving precision turns and proper spped control of your DC motor.

 

[jafaeldon]

you could use motor driver chips to control both speed and direction(forward/reverse).

i use L298 controller for my robots. each chip could control two motors at a time. to control motor speed use PWM in the enable pin. it also has an option to stop the motor immediately (dynamic braking i suppose)!

for precise steering, i recommend using either servo or stepper motors.