Motor Speed Controllers

[konk25]

Hi,

Can someone tell me how can we control the speed of a motor? I want to use a sensor or something so that I dont have to control the speed manually.

There are things like motor controllers but I am not sure if that works.

Your help will be great.

Thank you.

[aeniug2]

You would have to have a sensor collect data to be interpreted by the code, which would control the motor speed/direction through a motor controller such as a jaguar.

[Brandon_L]

The jaguars that came in your kit are motor controllers.

If you use the electricity-is-water analogy, the jaguars are like your faucet. it controls the flow of electricity to the motors. With a sensor and the right programming, you can control motors however you wish.

Victors are also another option, they function just like a Jaguar but work better with certain motors.
Spikes are another option, but are just on/off/reverse with no speed control.

EDIT: Worth noting that any sensors you use DO NOT plug into the Jaguar directly. They would hook up to one of the cRio slots. through programming you then adjust the motor speed.

[apalrd]

There are physical motor speed controllers, such as Victors and Jaguars, which adjust the voltage applied to the motor in response to software commands.

If you need more precise speed control (closed-loop), you would need a sensor which measures speed (such as an encoder, or if the speed is high enough a high-speed light sensor and code wheel on the shaft/wheel to be measured), and either code on the robot to control the speed or a Jaguar which internally does closed-loop control, but requires the CAN bus.

[Ether]

Originally Posted by Brandon_L

EDIT: Worth noting that any sensors you use DO NOT plug into the Jaguar directly. They would hook up to one of the cRio slots. through programming you then adjust the motor speed.

You can plug an encoder directly into the Jag. The processor in the Jag has software to do closed-loop speed control. You must be using CAN bus instead of PWM to access this functionality.

[Brandon_L]

Originally Posted by Ether

You can plug an encoder directly into the Jag. The processor in the Jag has software to do closed-loop speed control. You must be using CAN bus instead of PWM to access this functionality.

^^Correcto.

I use pwm, sorry.

[Al Skierkiewicz]

Kishan,
If you intend to control the speed of a motor without operator intervention, you need some method of telling the software what speed you want the motor to turn at. You can just turn the motor on to some predetermined value and let it run. Many teams want the motor to change speed under certain conditions or shut off when a condition has been met. For that application you will need something that senses the speed the at which the motor is turning at and an additional sensor that will allow your software to determine whether the motor is running faster or slower than you want or it has driven the robot to the prescribed distance. Many teams use some form of rotary encoder on the drive system for instance, to drive the robot in autonomous. This can be a gear tooth counter, a rotating encoder or a digital pot connected to the motor shaft or wheel shaft. The same holds true for mechanisms like arms. The motor is driven under software until a sensor on the arm is satisfied.