i need to calculate the time taken for a rotating wheel to stop, i.e i need the time from start of rotation to stop of rotation. I've to use IR sensors for this. I can stick a black or sort of strip, mark etc.
Can u plz help me out in this?
You need to publish what you have so far.
P.S. How will you know when the disc has stopped moving?
Thanks for the reply.
Ive thought of using the IR sensor. i thought of using black strips on the wheel, so that as and when the wheel rotates, IR Sensor detects it and counts it.
Dashingstar:
Thanks for the reply.
Ive thought of using the IR sensor. i thought of using black strips on the wheel, so that as and when the wheel rotates, IR Sensor detects it and counts it.
But how do you know the black strip is no longer passing the IR Sensor? After all, as the wheel slows the time between two successive black strips passing the sensor will get longer and longer and longer and longer. You will only know the wheel has stopped when the time between two successive black strips passing is infinite. Are you willing to wait that long?
Yea true! But i donno what to do. I want to calculate the time until the wheel stops rotating. Can i use a newton disc for this approach? As the disc rotates, it turns white which is sensed by the IR sensor. So untill the sensor reads 1 ill call timer? can this be done? Please tell if there is any other way..Thanks:)
The IR sensor detects IR and not visible light.
I really don't know how you can solve this since to be sure a disc has stopped you need to wait an infinite time. In your position I would ask my teacher how I should define 'stopped' in this context. Once you have this information then you can start your design.
its like i just turn the disc and it starts rotating. as soon as it starts rotating a timer should be called and as soon as it stops, the timer should be stopped
Dashingstar:
its like i just turn the disc and it starts rotating. as soon as it starts rotating a timer should be called and as soon as it stops, the timer should be stopped
We seem to be going round in circles. You need to define how to measure when "as soon as it stops" happens. Without that you cannot do your project.
Dashingstar:
its like i just turn the disc and it starts rotating. as soon as it starts rotating a timer should be called and as soon as it stops, the timer should be stopped
For simplicity, suppose you have a sensor that produces one pulse for every revolution. While the disc is rotating the Arduino can detect each pulse and measure the time from one pulse to the next.
But when the disk is moving very slowly there may be many seconds between one pulse and the next even if the disc has not actually stopped.
I have a program to control the speed of a small electric motor and my program assumes the motor has stopped if the time between pulses exceeds 60 millisecs. Because of the load on my motor it will almost certainly be stopped rather than moving even slower than that so it is safe to assume the motor is stopped without actually knowing for certain that it is.
You will need to make a similar judgement about your disc.
...R
good solid stuff from Robin. Then google 'rotary encoder', understand principle of how they are used and see if that gives you any ideas.
Dashingstar:
its like i just turn the disc and it starts rotating. as soon as it starts rotating a timer should be called and as soon as it stops, the timer should be stopped
What if the disc stops and the IR sensor is 'blocked'?
What if the disc stops and the IR sensor is *not *'blocked'?
123Splat:
good solid stuff from Robin. Then google 'rotary encoder', understand principle of how they are used and see if that gives you any ideas.
Rotary encoder background still won't deal with the fundamental problem of deciding what defines the disc as being stopped.
stowite:
Rotary encoder background still won't deal with the fundamental problem of deciding what defines the disc as being stopped.
That's what I was trying to convey and why I said in Reply #8 that judgement would be required.
...R