Sensor for counting...

darrenj · Mar 20, 2006

I am looking for sensor to "Count" product..Now before anyone jumps in and says use a photoeye..thats what we have..however its not accurate enough...

We are counting Milk bags Don't know if the people in states have seen them but they are tied the same way a loaf of bread is tied..the problem is when we view from the side the end of the bag (After the twist tie) catches the eye giving it a false count..Now if i put a time delay in to "debounce" we could miss the next bag if the spacing is off.. We run into similar problems going from above. It would also be nice if the sensor could tell if the bag was ripped and send perhaps a "reject" pulse or something along those lines...

I guess what i am thinking is a vision system..any other ideas (Cost effective!!) out there..

D

russrmartin · Mar 20, 2006

Is the eye viewing from the horizontal postion, and looking at a bag that is full and lieing on it's side, or standing up or what. It would seem to me that this would be simple with some mechanical engineering. Perhaps use a flow of air to direct the empty part of the bag that is not holding milk out of the way of the eye, or something to that effect. Get creative.

CroCop · Mar 20, 2006

Are you using diffuse or retroreflective?

darrenj · Mar 20, 2006

CroCop said:
Are you using diffuse or retroreflective?

Tried both..reflective for side viewing and diffuse for top..The problem with the diffuse is positioning..Its very finiky!..To close and it counts the conveyor to far and it misses the bag..just right..catches the tail of the bag..i end up with the same as a side view..

darrenj · Mar 20, 2006

russrmartin said:
Is the eye viewing from the horizontal postion, and looking at a bag that is full and lieing on it's side, or standing up or what. It would seem to me that this would be simple with some mechanical engineering. Perhaps use a flow of air to direct the empty part of the bag that is not holding milk out of the way of the eye, or something to that effect. Get creative.

Yes its lying on its side..

Yes you are right it seems simple..However Nothing in life is easy!!

The air flow works to a point but not quite close enough...

They basically want balls on accurate..They either have bad counts or product going out the back door..before they go down the "back door" avenue they want to rule out 100% bad counts..

CroCop · Mar 20, 2006

How bout you flip it?
Sense the conveyor, and monitor for a change outside of sensing the conveyor?
Or if you have analog, do the same with an ultrasonic.

darrenj · Mar 20, 2006

hmmmm not quite sure what you mean..?

I can sense the conveyor but then how do i detect if a bag has passed under?

By using ultra sonic do you mean mesuring the distance from sensor to conveyor and then waiting for a change?

would i still not have the same problem with the tag end?

Thanks

d

CroCop · Mar 20, 2006

I assume the tage end still causes the sensor to change states, correct?
Does the signal go:
low high low high
conv bag tie end

The tag end has got to be a different signal from the conveyor (distance) so analog should read different enough to catch it.

darrenj · Mar 20, 2006

Thats the problem..Look at a loaf of bread..the tag end is random..sometimes its higher than the bag..sometimes the same and sometimes lower..an air blast (Unless its a stupid amount of air) will sometimes not make a difference becouse of where the tag is placed..if its placed tight then there is more "frill" at the end..easy enough to push by air..If its tagged loose then there is not much frill..harder to push away by air..

you are correct the sensor on a perfect bag goes low high low high..however on a bag not tied..or tied a little off center the sensor stays high then low when there is no bag then back to high..this throws off the sequence of counts and realy buggers things up!

CroCop · Mar 20, 2006

Then the analog (if it's capable of picking up the bag tie) should have enough play in it to smooth it out to one digital signal.

What about background suppression?

stupidav · Mar 20, 2006

I have use the Banner Vision Systems for simular situations. I works great once it is setup, although I would have the factory rep show and demonstrate it. In certian situations it could possibly tell if the bag is ripped (depending on the color of the bag verses the milk. In US the price runs about $800-$1000, + what ever kind of light you would need. It will give you a count, although I am not sure what you are displaying the count on, but it does have Discrete outputs that you could possible use as well for the counter.

I used this on looking at lollipops to both determine if the stick was there and to make sure that the plastic was wrapped around the stick and not open. I my case I used the discrete outputs to tell good from bad and I kept track of the total count, via PLC and Operator Interface.

dale1627 · Mar 20, 2006

Try a light screen. For $350 you get 70mm detection height at 5mm resolution. Cheap and effective. Tried to post a link but it wouldn't work. Check out light screens at www.automationdirect.com
Item code: BX80B-1P-0H (pnp receiver-$190)or BX80B-1N-0H (npn receiver-$190). Plus you will need Item code: BX80S-10-0H (transmitter-$160).
You could use two screens to tell if the bag was torn also. Just set a second set higher than the first. If the first screen sees a bag but the second doesn't, then in all likelyhood it is torn.

Dale

darrenj · Mar 20, 2006

i see what you mean but if i smooth out a midrange low that is actally a transition from one bag to the next i will screw up the whole count? The tag is also a problem now that you mention it..the ultrasonic..would it pick up the tag?? i guess it would...

BTW are you familiar with our "Bags" of milk??

D

darrenj · Mar 20, 2006

here are some pictures of our bags

darrenj · Mar 20, 2006

O.K...i give up!!! I uploaded some images..how can i get them to display??

Sensor for counting...

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