Motor control

testikle

Hi Guys,

doing a project and am trying to figure out the most basic way to operate it.

Basically dc motor is used to turn a cog,it gets feedback from a position sensor,if the position sensor moves the dc motor activates and turns the cog in that direction(one way is fine)

whats the easiest way to control this,software programme,PLC,DAC,

Is there such a thing as an off the shelf PID controller for this application?

Appreciate any help or info

Thanks

TPM

Some more information on exactly what you need to do would help. the accuracy, distance you need to rotate.
It could be as simple as the position switch engages a relay which starts the motor switching the position switch then stopping the motor.

testikle

cheers for the reply

the cog will have to rotate 360 degrees(6 inch cog) and the position of the cog will be determined by the position of the external feedback sensor

accuracy is not very important once the motor turns the cog if the sensor is moved

limit switches wouldnt be any use as it needs to be a closed loop system whose feedback is from the sensor

hope ive explained ok

Bruthal

How does the sensor move compared to the cog?

On a radio control servo for example, the servo output shaft turns a potentiometer to get position feedback.

testikle

Hi Robbie

the cog moves in the same direction as the sensor,

e.g crane sits on top of movable cog,as wind direction changes so does the wind sensor the crane rotates to face the direction of the sensor automatically through the feedback of the potentiometer(wind meter)

just wondering whats the simlest way to demonstrate this as its only a simulation.

thanks once again

brightspark

is this a college project? what is your budget?

Bruthal

A servo connected to a pulse generator would be one way. Turn a pot connected to the pwm generator which generates between 1ms and 2ms for the servos left and right movements. A full rotation servo can be used, or else gear up a standard one by 4 to 1 or so.

I actually did a similar setup on a child`s electric ride on tractor before, a joystick to proportionally operate the steering.

I made the pwm generator for it from a 555 timer chip which is a simple enough circuit.

Since a servo already has a pot on its output shaft for position feedback, this would be a closed loop position sensing setup.

Maybe the project requires you use a standard dc motor?

testikle

Hi Lads,

yeah its a college project,how 200-300 to spend,

no specifics e.g dc motor,all i need in control loop,servo might be better alright

Bruthal

testikle wrote: »

Hi Lads,

yeah its a college project,how 200-300 to spend,

no specifics e.g dc motor,all i need in control loop,servo might be better alright

Yea servo`s are easy to make a manual controller for, using them 555 timer chips. They turn about 60 degrees each way for standard servos, but 360 degree servos can be got, and then get a potentiometer and some gears to turn that into a 360 degree rotation to match the servo.

That would probably be the simplest. 360 degree servos can be got from hobbyking.com amongst other places. They also have servo testers that move the servo manually with the turn of a dial.

2011

My classmate did this for a college project also using a Texas Instruments microprocessor. Speed feedback measurement was via an optical pickup and the microprocessor counted the pulses from this device to determine the speed. Speed control of the DC shunt motor was achieved with 0 to 10VDC pulse width modulation. The speed set point was via a pot and as far as I can recall it used PID controll.

It worked very well anyhow.

DublinDilbert

I would guess that the crane would turn quite slowly cause of the gearing. They don't accelerate very fast.

I would say 2 relays wired up in a forward / reverse set up would work fine. You could control these relays from a PLC or even an Arduino...

Something like this would work:-
http://talkingelectronics.com/projects/H-Bridge/images/ReversingRelay-3.gif