motor movement sensing

Hey everyone iam back for my second post...thanks a lot everyone for the replies for my first post,I really appreaciate it. Anyways I hve a new assignment. I have been told to use arduino uno in this project, although I dont think its required. But anyways to keep it simple, there is a conveyor belt, a conveyor belt is a belt which is used to transport material from one place to another, you guys must hve seen it in airports, anyways there is a conveyor belt which can move along both ways forward and backward. Basically I have to sense the movement of conveyor belt, so that when it moves in one direction it should give a HIGH signal or anything that sought and when it moves in reverse direction it should sense LOW signal or anything that sought.

I was thinking of attaching servo motor at the bottom of coveyor belt so that when it moves in one direction it could send HIGH signal to arduino uno and when the conveyor belt is reversed the servo motor wil be also be reversed in that case it can send a LOW signal to arduino uno, or something along that line. Any thoughts on this idea or any other idea would be really helpful. We also need to keep in mind that conveyor belt will be moving with the mains source voltage, and arduino only works in 5V.

Thanks

Why a servo? A simple encoder would be easier.

can you elaborate a little thanks

An encoder measures pulses, and depending on the pulses, the value calculated is either positive or negative. There are many example in the arduino playground, check them out.

A quadrature encoder would give direction. I don't see how you arrived at a solution involving a servo - can you explain your reasoning? Is there something you haven't told us?

actually i didnt come up with the motor idea..one my of colleagues did..he saw a video on youtube of this kind of mechanism and told me about it..he told me that he will post the video as soon as possible..possibly tomorrow or day after because he is not here currently...anyways i did read about encoders..rotary encoders I dont think would work in this case..because how will i attach the rotary encoder.to the conveyor belt.. quadrature encoder I will certainly look out for it..

any other ideas would be appreciable..thank you..

how will i attach the rotary encoder.to the conveyor belt..

with a wheel or knob pressed against the belt.

Hi, I think the use of servo was a mistake, just a motor connected to the belt will produce an output voltage when driven, the polarity different with direction of motor, and zero output for the most important output, Stopped. An encoder is more elegant, but it depends on costs..

Tom..... :)

... just a motor connected to the belt ....

Not sure how you just "connect a motor to the belt", easier said than done to be robust and reliable.

It may be easier to determine which way the motor which actually drives the belt is turning, rather than actually try to observe the belt itself.

If you want a non-contact method, there are small laser devices which can measure the speed and direction of things passing under them.

I suggest you tap into the mechanism that controls the direction of the drive motor - presumably there is a switch somewhere which selects the direction of travel. Sensing the position of the switch will be much easier than sensing movement of the belt.

cant i have some kind of push button activator..so that it when the belts moves in one direction the button will be pressed and signal will be send..and when it moves in other direction the button will be released...or smething along those lines..

There are lots of mechanical ways to approach it, but having no information about the mechanism we have no way to know which ones are practical. Doing it electrically via the existing control system would offer a much simpler and more reliable solution, though, if you have access to it.

Hi, I think the idea of observing the belt is the important part, if you monitor the motor or its control, you can have a broken or under tensioned slipping belt that will go undetected. So sensing the belt surface or a jockey wheel is the more favorable. A tacho or gen-motor or encoder connected to shaft of an undriven roller under the belt via flexible drive is probably as straight forward as you are going to get.

Tom... :)

there is nothng much to mechanism really...its just a conveyor belt..which has two belt cleaners perpendicular to belt at two opposite ends.when the belt moves in forward direction, one of the belt cleaners automatically comes down..and the opposite belt cleaner cleans it..when the conveyor belt moves in opposite direction vice versa happens..but i dont need to know all that.dats not my concern..

i just need a way to tell the workers working in head office that when belt moves in one direction, it should send a pariticular signal...so suppose its moving forward for 5hours..it sends a signal say HIGH.... through arduino RF modules..and then after 5 hours suddenly it starts moving backwards...then it should send a different signal either low..or negative current in case of motor..or somewhere along those lines...thats it..

Ok, what about this. Find out if the motor driving the belt is DC and not AC or 3 Phase. Because what you may be able to do is use Diodes connected to the motor wires to determine direction.

Say the belt is moving forward, the diode that is connected to the HIGH line will be outputting a voltage (with respect to ground), and assuming the LOW line is about ~0 Volts or ground, the other diode should be LOW; Reverse direction, the diodes reverse too.

riju:
there is nothng much to mechanism really…its just a conveyor belt…which has two belt cleaners perpendicular to belt at two opposite ends.when the belt moves in forward direction, one of the belt cleaners automatically comes down…and the opposite belt cleaner cleans it.

And there is your answer. Attach a magnet with a reed switch sensor to each of the belt cleaners. The movement sensing has already been done for you.

its an ac motor which is running the belt...

paul can you please elaborate..???

I think your colleague might have meant the servo motor that is really a DC motor with an attached quadrature encoder. these can be tiny toy ones or 3 phase 25 hp unit in industrial applications.

I have a bunch from an old printer. there is the simple DC motor, 2 wires and an attached encoder with multiple pins.

this unit can be wired as a generator to output a voltage relative to speed. and the encoder can output direction and speed.

As you mentioned, this has to be independent of all electronics, and for a multitude or reasons. reading the final device (belt) is the only way to know there is movement !

http://www.pololu.com/product/1217

found this. you can have the toy wheel ride on either the belt itself or one of the rollers.

riju: Paul can you please elaborate..???

Well, you said there are a couple of belt cleaners of which one comes down when the belt moves in one direction, and the other comes down when the belt moves in the opposite direction. So they already tell you which way the belt is moving, and you only have to attach a magnet to each of them with a reed switch sensor (as on a door for a burglar alarm) to know which one has come down and which way the belt is moving.

The job would seem to have been done for you already.