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Old July 19th, 2018, 09:56 AM   #1
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_Dock_ is offline
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Lightbulb Laser distance measuring (Time of Flight)

Has anyone used any of the laser distance measurement sensor, specifically time of flight type? Im thinking about trying one of these to do some positioning. The applications I have to use them are not best suited for an encoder. Right now we are using discrete with prox sensors and it can be a bear to get setup in the field.

If so, what were your thoughts? pros, cons, issues? I plan to use I/O link so I can read the actual value instead of using the discrete outputs. I will have a little more flexibility there. Just a little nervous as Ive never used any type of laser measuring device, ive always used encoders.

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Old July 19th, 2018, 11:18 AM   #2
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We have used this technology from Sick, Banner and Allen-Bradley. I know Keyence also has this available but we haven't tried them yet.

Our current favorite is the Sick DT35. We use this for incoming roll diameter measurement as well as rough positioning of accumulator carriages. If you are looking at them as prox replacers they would certainly be able to handle that. If you are going to use I/O Link you should be able to get millimeter resolution out of it.

The only real issue I have run into with them is that they seem to be surface color sensitive. I have no idea why this would be the case with a time of flight device but it seems to be. Also keep in mind that the specified maximum range is with a bright white target. If you are shooting at darker targets your maximum range will reduced due to lack of return light.

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Old July 19th, 2018, 12:02 PM   #3

thingstodo is offline
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+1 on Sick and Banner

We're using a retro-reflective tape on our Banner installs.

The older SICK units we have work from 0 - 25 meters with white gloss paint as the target. We clean them when the signal gets intermittent ... but it is feedback to operations on a position and they are controlling the position. No bad things happen if the sensor goes offline.

Last edited by thingstodo; July 19th, 2018 at 12:03 PM. Reason: typo
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Old July 19th, 2018, 12:09 PM   #4
John Morris
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Used this to fact check an encoder for a trolley placement.

It will pretty munch measure the diameter of a nat's ***

loop powered 24 vdc

set up programming is free, and there is plenty of support.
"When nothing is going right, go left."

"Even a fish wouldn't get into trouble if it kept its mouth shut."
(I should probably look into this)
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Old July 19th, 2018, 12:12 PM   #5
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I would recommend a Laser system over limit switches
I have been recommending and using them for years Fast install and very accurate.
For best results I recommend you use reflective target.
The brand would depend n the distance you want to measure and the resolution you are looking for.
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Old July 27th, 2018, 07:53 PM   #6
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_Dock_ is offline
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Thanks for the responses. I feel a little more at ease to hear that others have had success. I’m confident in our abilities to make it successful but still Leary of the hardware.
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Old July 27th, 2018, 09:11 PM   #7
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I’ve used the Keyence LR-T and was very impressed with it. My application was not a distance measurement application so cannot speak to that. I had to use a time of flight since I was detecting products of varying color, emissivity, shape (inconsistent round edges), and transmissiveness. The TOF sensors are very impressive and I wouldn’t hesitate to try one if I needed distance measurement and could set up ideal or semi-ideal conditions.

I would not expect accuracy better than 1-3mm though. If you need a better accuracy than that over a long distance I would look to a cable encoder or mounting an encoder wheel to the device that is moving.
Anything is possible, when infinite resources are available.
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Old July 27th, 2018, 09:26 PM   #8
Peter Nachtwey
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What kind of accuracy to you get?
Think of the frequency of the counter required to get 1mm resolution.
The rise time of the detected signal will cause a lot of variation.
"Living is easy with eyes closed, misunderstanding all you see...." Strawberry Fields Forever, John Lennon
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Old July 28th, 2018, 07:53 AM   #9
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roxusa is offline
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What is your min/max distance, I am currently using:
OPT2011 Wenglor photoelectric laser sensor, diffuse, 50 x 50 x 20mm, Class 1 laser light emission, 0.05-3.05m sensing distance, 18-30 VDC operating voltage, NPN/PNP, 0-10 VDC or 4-20 mA analog output, 4-pin M12 quick-disconnect.
Automation Direct $300
if you are going to assume, assume you're wrong.
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Old July 28th, 2018, 05:06 PM   #10
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We started using these a few years ago and have been very satisfied. If you have a very dusty or steamy environment, you could have problems with false reflections. The lens is reasonably tolerant of crud but that's another thing to consider. Grease the connector threads in a caustic washdown environment.
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