Hey All, Could we use timed cheapo laser pulses to measure Z?

Hey Peeps,

I was thinking about some laser diodes i have and the forever Z problem.

Is the Arduino accurate enough to measure short light distances?
There are laser tape measures begging to give up their lives for science, haha.

Send a 10 microsecond pulse, maybe IR, at a certain time and see when a photo-something reacts??? ???

Non-contact, accurate as anything, 2 components and a bit of code.

I am on it complete, and I would luv help/ideas/proofs of time wasting?/talk.

Thanks all,
flyCouch.

I've looked at the idea and wondered about it, but seeing the high cost of professional laser measure with enough accuracy for my liking I've not gone anywhere with it. If you could develop something, I'd be all over that.

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Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus

Hey MrDoctorDiv,

I have imagined a test that could be performed, as soon as my medium coding skills/time allow.

We code the laser to trig for 10uS.
Next lines of code time the mirrored pulse.
We adjust the mirror distance to play around.

Can we get representative numbers when we change the distance?

I will check eventually, I have a illness to continually deal with.
If anyone could try this experiment and post something, that would be super great.

Peace,
flyCouch

Hey OK,

here is a downer but maybe we could use slower sound/ultrasound waves.

The Arduino operates at 16 mhz, which is 62500 cycles/second.
If it takes 200 cycles to perform the operations then it will take .0003125 seconds to perform the operations.
Light travels 300 meters in 1 millionth of a second, so, in Arduino time, light will have travel .09375 meters. Too far.

Maybe, if you wrote some really fast efficent code.

Likely better with ultrasound kits, already made for Arduino, can they get the accuracy?

Still hoping... ...
flyCouch

... better think about a triangulating setup - e.g. a skewed laserpointer and a web-cam measuring the XY-position of the spot ...

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Viktor
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Call for the project "garbage-free seas" - [reprap.org]

Very Cool, Viktor, good idea.

Isn't one of the RepRap philosophies that it is reproducable cheap and easy, good job Sir.
If the webcam is meter away u could likely get well magnified amounts of reporting to the Arduino.

So who knows how to get info from a webcam?

I am going to order one of the Arduino ultrasound kits anyways, they are like, $4-5.

ta,
flyCouch

Lasers *4, all 4 corners, 1 webcam.

whatever method you use make sure it includes fail safes such as additional hardware limit switch. you never know when an alternative method will act up. there is nothing worse that a overcompensated z and and a print job pending. the nozzle and heater can easily get scrapped if fail safes are not included and filament oozes thru a nozzle that has scratched a heated bed.

also many people have had success with probes. it is known that z does not always zero out properly. probing helps this issue dramatically.

hmmm, 10-4

Expanding on VDX and MrDoctor Div,

Maybe tiny precise brackets in the 4 corners of the bed pointing lasers to the printhead when it exactly 30mm Z and XY center and the bed is level.

Very easy, I am thinking.

I might even have the skills, imagine.

Oh, or you can try first, I would be happy to download your *.stl for them.

I got my lasers for 60 *cents* apiece.

flyCouch
out

a selection of 4 diff colored lasers would make it easier...

Laser measuring devices are expensive because the need expensive components and smart programing.
You may think of a very fast time measuring module with laser and photo sensor, with a very fast processor to get the time of travel.
Also lengthening the distance by bouncing the laser line around known distance mirrors.


Some education in mirror testing, laser range finding, LIDAR, could be beneficial.
There is time of flight and phase shift measuring techniques.

Have you thought about counting the lines of a diffraction pattern, as the go by, to measure distance down to angstroms.
Time-of-flight measurements are preferentially used for large distances!

[www.rp-photonics.com]

[www.rp-photonics.com]

A laser and photo diode plugged into an Arduino is not going to work!!

Have Phun

Just getting around to thinking about it [and doing no math] but does an Arduino even have a single clock short enough for measuring such a short time?

---

Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus

[en.m.wikipedia.org]
A nanosecond (ns) is an SI unit of time equal to one billionth of a second
Light travels approximately 29.9 centimeters in 1 nanosecond.

So to get an accurate pulse measurement to within even 0.1 mm, you would have to fire a pulse and then catch it within 1 300 billionth of 1 second.
Good luck with that one...keen to see what you come up with using an arduino and a $0.60 laser :-)

Hey,

So, if we need .01 mm accuracy and laser wavelength is around 5000 um.

Then, 299792458/5000=59.96 Ghz frequency

Say we need 10 CPU cycles to perform it, then about a 600Ghz computer should do it , now I just be funny.

I like the lasers reflecting off the surface ideas, lots to measure there, easy peasy... ...

And/or, have 4 corner lasers point to a predetirmined spot hardware/software wise and adjust till the 4 colour lasers are at the spot.

I checked, the common ultrasonics for Arduino have a resolution of about .5"
If we built similar but at 100 times the frequency...

reprap on!!
flyCouch

If you have a laser at a specific angle and location, and you adjust Z until it hits a sensor, at a known location and angle, then you should be able to calculate your z-height.

I've been thinking about the idea of a laser for delta calibration-- the first half of the idea was to fire a laser through the middle of the bed, and when the filament tube lights up, the hotend should now be centered, and the offsets should be correct.

The other half of the idea is to use a laser/mirror at a precise angle, pointed at a sensor on the corner of the bed,also at a precise angle. If you know both angles, and the X distance between the two ends of the beam, you should be able to calculate your height. Obviously, the precision of the angles, and the measurement between the points will affect the final calculations.

Haven't quite figured out how to put both halves together to automate the process, but it should be possible.

The sensitivity required for the range-finding by turnaround time is probably a bit beyond the current commodity tech level used in 3D printing.