Sensor advice needed

I need a kind of a light curtain, measuring the width of passing object (that is, the number of interrupted beams).
Output signal format is not critical at this point.
The maximum object width will be ~16"/400mm, the resolution of 3/8"/10mm is sufficient.
The device does not have to be safety rated.
It must be a serially produced device with reasonable delivery time.
The cost matters

Any suggestions will be highly appreciated.

You could use an LVDT possibly if there is one particular spot you can beam down and to get the height of the object.

If you are doing it side to side, you could use a pair of LVDTs and take the difference.

Banner I think makes these now, but the Valuscan light curtains from STI do exactly what you want, and I think they still offer the same features under the Omron umbrella.

http://www.stiscanners.com/measuring_light_curtains/valuscan_VS6500.html

We used these with both serial and analog outputs. Their analog modules, out of the box, new were scaled 0.000 to 10.000vdc +-0.001vdc every time. This was an outstanding product ten years ago, and probably still is.

On the bench I used Hyperterminal to set them up serially, and they can be configured to count holes, set a value for highest or lowest beam blocked and more.

EDIT: And they can be configured to output a serial stream representing the beam pattern if that is what you need on the other end of the serial stream, and you can probably then confugre an ascii message to automatically configure the VS6500 with the controller.

DamianInRochester said:

You could use an LVDT possibly if there is one particular spot you can beam down and to get the height of the object.

If you are doing it side to side, you could use a pair of LVDTs and take the difference.

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OOPs..... Please substitue LVDT from above with LDS. I really meant laser displacment sensor.

Sergei Troizky; said:

It must be a serially produced device with reasonable delivery time.

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Wait, did you mean unique serial numbers for some sort of standards compliance? Or serially as in habitually over a long period of time like a cereal killer?

I thought you meant serially interfaced, which is slick with the ValuScan.

cereal killer?

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yes honey bunches of oats are my favorite victims LOL

Nah, Raisin Bran, and Honey Nut Cheerios. I have always said, Raisin Bran should come in five gallon buckets, now at Sam's I buy the dual box which is close to that. I am like Jethro Bodine the cereally connected cereal killer, or worse...one box of family size corn flakes would last two days here, and I eat Braum's Oatmeal raisin cookies by the dozen and two gallons a week of their delicious milk.

OkiePC said:

Wait, did you mean unique serial numbers for some sort of standards compliance? Or serially as in habitually over a long period of time like a cereal killer?

I thought you meant serially interfaced, which is slick with the ValuScan.

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I meant an item produced in quantities and with reasonable delivery time.

Sergei Troizky said:

I meant an item produced in quantities and with reasonable delivery time.

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Why not use a simple photoswitch with an encoder on the belt that conveys the product (I assume it's on a conveyor). If the belt speed is consistent, an encoder won't even the necessary. Let's say the belt speed is 15FPM. If the sensor is blocked for 4 seconds, the object is one foot long.

Sergei Troizky said:

I meant an item produced in quantities and with reasonable delivery time.

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Not sure about quantities, but they have been around a long time (valuscan).

Are you wanting to snapshot the length of a box after it is at a certain point traveling along the length of a conveyor without stopping?

If they are nice and square the through beam (fast) registration eye and high speed encoder counter are a good idea. I saw one done with an encoder wheel that dragged across the top of the cases to measure them quite accurately on a jerky conveyor, and when the case passed under it, it tilted up, making the z-marker input on the counter card with a plain microswitch on the bracket. All those boxes were the same size though.

I think to profile length with the valuscanner, you would want to get the relay board and configure it to trigger when a certain beam is blocked, and then take a snapshot of the analog signal configured for the number of beams blocked by the largest object. The length to order might be tricky in that layout depending on the gap size to avoid having to mask out leading or trailing edges. The serial stream is pretty slick too. I remember setting it to stream to hyperterminal and watching the binary pattern on the screen scroll by as I waved my hand and products through the curtain. It is quite fast, accurate, and just cool. It would not be hard to count the bits blocked and the gaps too in ladder logic from a digital stream, except it starts as ascii...still not too bad though and you then have all the information from the curtain at your disposal.