Decreasing voltage to motor

[mollekake]

Hello all.
I am wondering about something.
I have this thing i'm working on, and i have motor.
I want to slow it down, which i assume i can do by decreasing the voltage output to it.
So my question is, how do i do that most effectively?
im going to connect it to a microcontroller and have it go at different speeds, depending on which pin i output to.
The microcontroller i have is a PIC16f1824 (my last one )

Any help is appreciated

 

[Arouse1973]

Use PWM for this. If you don't run the motor out you could have issues like increased current consumption which could damage the motor. You also reduce torque, it is better to operate a motor with full supply for a shorter amount of time.
Adam

 

[shumifan50]

If you don't fancy building it yourself, you can get motor speed controllers from many hobby shops or robotics sites. But it will depend on the size of the motor and its power requirements. I have also found that not all motors handle PWM well - some lose power quite quickly when the duty cycle decreases, some become very noisy.

 

[KrisBlueNZ]

http://www.robotroom.com/PWM5.html

 

[mollekake]

Thanks guys. Not used PWM before. Got any tutorials or good guides for a newbie on PIC PWM?

 

[shumifan50]

The PIC data sheets document it quite nicely.

 

[(*steve*)]

Talk about pushing him in off the deep end!

Here is an example circuit using a 555 to do what you want to do. I have some reservations about their circuit, but it may do what you want.

 

[shumifan50]

Some off-the shelf speed controllers:
http://www.technobotsonline.com/motor-controllers/variable-speed-motor-regulators.html

A selection of single chip H-bridge drivers. You will need something like this to handle the current to the motor.
http://www.technobotsonline.com/sem...r-and-drivers/h-bridge-and-motor-drivers.html

 

[BobK]

A selection of single chip H-bridge drivers. You will need something like this to handle the current to the motor.
http://www.technobotsonline.com/sem...r-and-drivers/h-bridge-and-motor-drivers.html

Only if the motor needs to be reversible. A single MOSFET will work otherwise.

Bob

 

[shumifan50]

Only if the motor needs to be reversible. A single MOSFET will work otherwise.

Bob

That is true. I did not stop to think. I have only used PWM for blind control and needed bi-directional control.

 

[Arouse1973]

That is true. I did not stop to think. I have only used PWM for blind control and needed bi-directional control.

You can also use the H Bridge as a motor break if you need to slow it down quickly.
Adam