motor speed control and pic

[laki101]

I have an 12v (about) 1-1,5A dc motor and I wont to control it with an pic. Beacause of the voltage and amperage I gues I must use an H bridge. And I am making one using 4 transistors.
Now I have no idea on how to make it possible for the pic to have speed control.

 

[birdman0_o]

Which PIC, use PWM. Which language are you coding in?

 

[laki101]

pic 16f877 (probably) , basic language

I heard about PWM but im not sure how to conect it with the transistors and how to programe the PWM

 

[birdman0_o]

Well, it's not that bad, read the data sheet, has everything you will need. The pic16f886 has a better PWM module, one meant for a full H bridge.

 

[laki101]

and I was thinking on making a H bridge with just 4 transistors could that do

 

[birdman0_o]

Yes, but I still suggest the 16f886, look at it's data sheet in the PWM section

 

[laki101]

well I can only get the 874,7,8 which is an older version of the 884,7,8 so I think it will just do fine

 

[birdman0_o]

Where are you from?
Yes of course it will work, but it will be slightly trickier, especially for turning.

 

[laki101]

I am from Serbia. I mean I could probably find here an 887 but in the shops I buy they have the 877 so I will have to do with that

 

[nigelwright7557]

PWM will sort of work but it wont react tightly without using some sort of PID technique.

 

[MikeMl]

I have an 12v (about) 1-1,5A dc motor and I wont to control it with an pic. Beacause of the voltage and amperage I gues I must use an H bridge. And I am making one using 4 transistors.
Now I have no idea on how to make it possible for the pic to have speed control.

Do you just want speed control with the motor only turning one way, or do you need to reverse the motor?
Are you trying to make a closed-loop speed control?
Does the motor have a provision for a tachometric speed signal (pulse rate proportional to shaft speed?

 

[laki101]

both directions

I have no idea whats a closed loop speed control

the motor is an really old wiper motor so it just has 3 wires slow speed, fast speed and - ,but it can speed in both directions when changing the polarities

 

[MikeMl]

Closed Loop speed control is a feed-back system where you command the motor to turn a given speed. There is a sensor attached to the motor shaft which gives a signal proportional to shaft speed. The actual shaft speed is compared to the desired (set) shaft speed, and the controller automatically increases or decreases the average current to the motor if it is running either slow or fast.

Sounds like you just want open-loop (no feedback, no sensor) control.

Do you want to use the HI/LO speed wires, or will you just use one or the other?

 

[laki101]

I just need an open loop and just to use the hi speed wire
so just like I would use a speed control circuit with a potentiometer to use the pic for that ,and one day to make the pic turn the motor based on the music ,but first just a pre-programed control sistem