## Measure Length,Width and height

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Hello

here is my qouestion

I have differnt size carboard boxes like image below

my objective is to measure the Length,Width and height using sensors or camera and send it via rs232.

what is the easiest and low cost method to do it?

many thanks

~ Chandana ~ a self learner

Last Edited: Tue. Feb 6, 2018 - 09:56 AM

How good? 1mm 1cm 1 inch.....

Do we know how it's placed, can it be moved (is it moving).

....

A set of digital calipers with a serial output port?

"This forum helps those that help themselves."

"How have you proved that your chip is running at xxMHz?" - Me

"If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

That sort of asks my question - does this have to be done "hands off" ?

Are these boxes moving past on a conveyor belt or something?

Are they in any random orientation?

If they were "lined up" then two dimensions could be taken with a grid of lasers and if the speed of the conveyor is know (monitored?) then the time taken to pass gives the other dimension.

As someone employed in vision engineering it's temping to suggest an optical processing solution. Because this is a "canned environment" presumably the floor and walls around the box could be covered in "checker board" which could aid the optical processing immensely When cars with cameras are having the cameras calibrated in the the factory they do so on such a grid. This kind of thing:

Oh and what is the budget? £1m, £10,000 or a tenner?

A 35E\$ Rpi + 45E\$ camera + 20 E\$ ("disk ", ethernet wire) might do the job, according to Clawson (one needs to install opencv/pyopencv, which is very easy; fixed background substraction and  detecting lines and corners is very trivial -tutorial parts ; bet google "line detector opencv will find it out"- then; if things are hidden (one box hids other box's corner, it gets far from trivial, however-)

.

Perhaps add an I2C ultrasonic sensor (AFAIK, it is supported by RPi); if reliable anough, might give an extra information...

Edited :

PC, even very old ones (making budget random and likely very low) can have OCV and webcams (advantages: one can find old PCs. and webcams everywhere; cons : if a checker board is printed on paper, might wear out/ get wet.)

Last Edited: Tue. Feb 6, 2018 - 12:07 PM

Lidar is becoming cheaper as technology moves forward. Using a scanning technique you can measure the box to within millimetres. Other possible techniques is if you can move the box in a given direction and measure the movement, then simple laser beam interruption is cheap. Ie: measuring length is simple on a conveyer belt by having a rotary encoder to measure belt distance. Move the box through a laser beam, noting the distance when it first breaks the beam and then when it clears the beam. Measure the height and width by using non contact distance sensors from the likes of Banner and Sick.
ST microelectronics have some nifty (and cheap) distance sensors thst are good for around 20cm -
http://www.st.com/en/imaging-and-photonics-solutions/vl53l0x.html

How about a lever connected to a rotary encoder? Move the box under a lever, box lifts the lever then measure the angle. If you know therange of sizes of the boxes, then a potentiometer would probably be accurate enough to infer the box size.
There’s also been some interesting work done with the Microsoft Kinect camera. I saw a university project that mapped the contours of a sand pit in near real time.

So many options.

Last Edited: Tue. Feb 6, 2018 - 11:51 AM

If you just want to distinguish several standard boxes,   simple light beams that get interrupted as the box moves past on the conveyor.    You don't need mm accuracy to detect different sizes.

Mechanical spring arms can line up the boxes as they enter the light beam station.

I doubt if cardboard boxes require precision measurement.

David.

Surely the OP knows all of the size data of his box population and perhaps there is one dimension that is not duplicated in the rest of the population. Measure that and it will automagically identify the member and a lookup will produce the other two dimensions.

Ross McKenzie ValuSoft Melbourne Australia

If you are having boxes made then get the manufacturer to put a barcode on them and use a simple reader.

"This forum helps those that help themselves."

"How have you proved that your chip is running at xxMHz?" - Me

"If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

Cat Skinning 101

Ross McKenzie ValuSoft Melbourne Australia