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Topic: Measure the distance to a spinning saw blade? Ultrasonic? (Read 754 times) previous topic - next topic

TomB19

Hi!  New here but not new to Arduino.  :)

I need to measure the distance to a spinning circular saw blade.  Specifically, I'd like to be able to measure the depth of cut of a table saw, circular saw, jointer, router, etc.  It would be really nice if it was accurate to +- 0.015.

The blade will need to be spinning because I want to measure the distance to the tip of the blade and not the relief areas.

My hunch is, a saw blade singing at full speed is not going to be easily tracked by an ultrasonic distance sensor.

Any other ideas?  I don't mind trying a few things to see what will work.

Thanks!

AWOL

Quote
It would be really nice if it was accurate to +- 0.015.

Parsecs?
AU?
Metres?

40kHz wavelength in air is around 8 or 9mm
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Shpaget

It would be really nice if it was accurate to +- 0.015.


What units are you talking in?

edit:
Beaten to it I guess.

robtillaart

Quote
My hunch is, a saw blade singing at full speed is not going to be easily tracked by an ultrasonic distance sensor.

you should try to be sure

IR might be another option

capacitive?
Rob Tillaart

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TomB19

Wow, you guys are quick!  Thank you so much.  :)

- Desired accuracy: 0.015 Thousandths of an inch (1/64")
- Desired range: 0.5~4 inches

I think I have an ultrasonic sensor kicking around somewhere.  I'll give it a try and see what happens.  I should not have assumed it would not work before trying it.

Shpaget

#5
Feb 23, 2013, 07:21 pm Last Edit: Feb 23, 2013, 07:25 pm by Shpaget Reason: 1
0.015 Thousandths of an inch != 1/64"

Even at 1/64" you're still a few orders of magnitude away from feasible accuracy precision.


Edit:
http://www.ti.com/lit/an/slaa136a/slaa136a.pdf
This thing is working at 40 kHz
Quote
The distance is displayed in inches with an
accuracy of ±1 inch.

Harrzack

Tom - depth of cut will be tricky, as the portion of the blade contacting the work material will be buried/not in view.

How about using a good rotary encoder (maybe even optical, but they get pricey) on your blade height adjustment?  This would be a good excuse to create a digital readout on the Arduino as well.  XD  Naturally the accuracy will be limited by how many bux you are willing to drop on the encoder.

Then you can calibrate where the top of the blade is relative to the surface of the machine, and work from there. There prob will be some play in the height-adjusting screw so you'd need to allow for that in each use.

Another help for setting it up would be to have a DC voltage (9v battery, etc) tied to the machine,
and make a non-conductive height gauge with a metal contact surface. This would set on the table surface, and when the blade touches the contact, the circuit is closed, and an LED would light - and you can read the height from you digital display.

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