Arduino Forum

Using Arduino => Sensors => Topic started by: nmlfreitas on Oct 09, 2012, 07:18 pm

Title: Measure distances in mm
Post by: nmlfreitas on Oct 09, 2012, 07:18 pm
Hello guys
I'm not new with arduino and electronics, but i have a question that i need to ask to people that know a lot more then me.
I want to use a sensor with arduino to measure from 0.8mm to 6 or 8mm. I have a machine that is always working with wood sheets and i need to read the thickness of the sheets with the machine working, do you think it can be done with CNY70 optical sensor?
If not is there another sensor that can do it?

Thanks guys
Title: Re: Measure distances in mm
Post by: CrossRoads on Oct 09, 2012, 07:19 pm
Got a link tothe CNY70 datasheet?
Title: Re: Measure distances in mm
Post by: pylon on Oct 09, 2012, 07:57 pm
What accuracy do you need/expect? Is the surface of the sheets always the same (color, smoothness, etc.)?
Title: Re: Measure distances in mm
Post by: nmlfreitas on Oct 09, 2012, 08:33 pm
Thanks for the quick reply.
The sensor datasheet http://www.vishay.com/docs/83751/cny70.pdf (http://www.vishay.com/docs/83751/cny70.pdf)
I need an accuracy like 0.8mm to 0.82 or 0.85 more less.

Thanks
Title: Re: Measure distances in mm
Post by: CrossRoads on Oct 09, 2012, 08:49 pm
Spec shows output will very from 0.1mA to 1mA, you'll have to take that use an op amp like this
http://www.dipmicro.com/store/index.php?act=viewProd&productCode=TLC279IN
to convert it to a 0-5V signal that the arduino can measure.
From Figure 11 the change in current between 0mm and 1mm is quite small.
Title: Re: Measure distances in mm
Post by: nmlfreitas on Oct 09, 2012, 09:06 pm

From Figure 11 the change in current between 0mm and 1mm is quite small.

So that means if i want to detect changes from 0.8mm to 0.85 or 0.9 it will be hard or almost imposible right?
Any other sensor that it's possible for me to use?
Title: Re: Measure distances in mm
Post by: Grumpy_Mike on Oct 09, 2012, 09:30 pm
Yes you are asking too much from this sensor.
I assume you want a non contact sensor? It is quite difficult to do this and I don't know of any off the shelf sensors that will do this.
It might be possible to use a reflection of a laser onto a linear CCD sensor but it is not an easy setup.
Title: Re: Measure distances in mm
Post by: CrossRoads on Oct 09, 2012, 09:51 pm
You might be better with a mechanical dial kind of tool with digital output. Not sure what that is called.
Title: Re: Measure distances in mm
Post by: Grumpy_Mike on Oct 09, 2012, 10:07 pm
You mean one of these
http://engineerblogs.org/2012/02/awesome-tools-for-every-mechanical-engineer-by-sam-feller/ (http://engineerblogs.org/2012/02/awesome-tools-for-every-mechanical-engineer-by-sam-feller/)
Title: Re: Measure distances in mm
Post by: CrossRoads on Oct 09, 2012, 10:11 pm
No, I mean something digital like one might find on an incoming-inspection table, or perhaps a calibraton table, for automatic recording of results.
Title: Re: Measure distances in mm
Post by: RIDDICK on Oct 09, 2012, 10:32 pm
what about a webcam (properly affixed with screws or so... connected to some stable USB box... like an OLinuXino (https://www.olimex.com/Products/OLinuXino/iMX233/)...) that looks at the piece from the side?
Title: Re: Measure distances in mm
Post by: nmlfreitas on Oct 09, 2012, 10:42 pm
You mean something like this

http://www.microsense.net/products-position-sensors-selector-thickness.htm (http://www.microsense.net/products-position-sensors-selector-thickness.htm)

?

A webcam to measure thicknesses??

Title: Re: Measure distances in mm
Post by: RIDDICK on Oct 10, 2012, 12:15 am
nope
not capacitive but optical...
or is it impossible to look from the side?
Title: Re: Measure distances in mm
Post by: nmlfreitas on Oct 10, 2012, 12:38 am
yes i can be measured from the side if that is what you are asking.
But your are saying that the capacitive is not going to work for me?

Thanks
Title: Re: Measure distances in mm
Post by: Nantonos on Oct 10, 2012, 12:50 am

No, I mean something digital like one might find on an incoming-inspection table, or perhaps a calibraton table, for automatic recording of results.


This sort of thing?
http://www.tormach.com/store/index.php?app=ecom&ns=prodshow&ref=31761
plus USB interface
http://www.tormach.com/store/index.php?app=ecom&ns=prodshow&ref=31865
Title: Re: Measure distances in mm
Post by: nmlfreitas on Oct 10, 2012, 12:58 am
I can't use that type of things you just mentioned because the wood is always "runing" on the machine...
Title: Re: Measure distances in mm
Post by: MarkT on Oct 10, 2012, 01:21 am
Something like this (but better) perhaps?  http://media.digikey.com/pdf/Data%20Sheets/Sharp%20PDFs/GP2Y0AH01K0F.pdf (http://media.digikey.com/pdf/Data%20Sheets/Sharp%20PDFs/GP2Y0AH01K0F.pdf)
Title: Re: Measure distances in mm
Post by: CrossRoads on Oct 10, 2012, 04:17 am
Yes, that's the kind of thing I was thinking of.
Title: Re: Measure distances in mm
Post by: RIDDICK on Oct 10, 2012, 08:17 am

A webcam to measure thicknesses??


yup - u would need to do some image processing...
the machine parts (in the background) should have a much different color than the wood pieces...
how fast do those pieces pass the sensor? less than 25Hz?
Title: Re: Measure distances in mm
Post by: nmlfreitas on Oct 10, 2012, 09:09 am
That Sharp sensor would work form me the minimal distance is the problem, i need 0.8 mm and for what i've seen they don't have that kind of sensors.
Do you think that this would work?
http://www.baumer.com/int-en/products/product-finder/presence-sensors-measuring/#pfinder_sensor/scripts/level2.php?language=en&header=&country=CH&cat=CONFMyAppli&psg=madynGrundfunktion2|1993482997,madynPGGrundfunktion|Optisch&pid=&ptk=&viewmode=&filterViewMode=&perpage= (http://www.baumer.com/int-en/products/product-finder/presence-sensors-measuring/#pfinder_sensor/scripts/level2.php?language=en&header=&country=CH&cat=CONFMyAppli&psg=madynGrundfunktion2|1993482997,madynPGGrundfunktion|Optisch&pid=&ptk=&viewmode=&filterViewMode=&perpage=)  

Check the ZADM 034
(ParCon, analog output)

Please
Title: Re: Measure distances in mm
Post by: RIDDICK on Oct 10, 2012, 03:28 pm
the specs look good...
the accuracy is much better than u need: 50um...
Title: Re: Measure distances in mm
Post by: nmlfreitas on Oct 10, 2012, 05:07 pm
Yes i know but do you think it is hard to connect it and make readings with arduino?
Title: Re: Measure distances in mm
Post by: RIDDICK on Oct 10, 2012, 08:16 pm
it seems to b easy:
1. connect 12V to it...
2. connect wires for the output like this:
GNDsensor-----------------------wire#1-------------------100R(or similar)-----------------------wire#2-------------------OUTPUTsensor
3. calibrate the arduino (i would use the INTERNAL ADC ref, which should give u reproducible results at the same temperature/voltage):
http://arduino.cc/en/Reference/AnalogReference?from=Reference.AREF
Title: Re: Measure distances in mm
Post by: Grumpy_Mike on Oct 10, 2012, 09:50 pm
It has a current loop output so you need to calculate your load resistor cairfully. Also there is a 4mA output minimum so you will get a fixed offset voltage. Given that you might have to do some messing about withan op amp to give you the full range of the A/D.

However have you looked at the price of this? I can't see one which is never a good thing. I would expect this to be in excess of £200.
Title: Re: Measure distances in mm
Post by: nmlfreitas on Oct 11, 2012, 12:29 am
I've send email today requesting price still waiting for response.
Title: Re: Measure distances in mm
Post by: cr0sh on Oct 11, 2012, 06:39 am

Check the ZADM 034


I was about to mention these - they are basically close range LIDAR devices. I can guarantee you they -will not- be cheap. Grumpy Mike is probably right on target (if you can even find a distributor that will sell to the public and only sell you one of them)...