Is it possible to increase the accuracy of the PING))) Ultrasonic Distance Sensor?
idbruce
Posts: 6,197
Hello Everyone
Assuming a distance range of up to 3", is it possible to increase the sensitivity of the PING))) Ultrasonic Distance Sensor to 0.001"? If not, then what distance can this sensor be modified to monitor?
Bruce
Assuming a distance range of up to 3", is it possible to increase the sensitivity of the PING))) Ultrasonic Distance Sensor to 0.001"? If not, then what distance can this sensor be modified to monitor?
Bruce
Comments
IIRC it's between 1 and 2 mm.
Last week I had an echocardiogram. They use transducers that output ultrasound in the 4MHz range. If you could find a higher frequency transducer, you should be able to increase the precision of an ultrasound range finder.
I will have to do an in depth search to see what kind of solutions are actually available for a reasonable cost.
And before anyone mentions "lasers" (not referring to you Duane ), let me just say that I am trying to avoid the use of light, because I will be measuring the distance to a photosensitive film. However, I suppose I could use a light source that is outside the wavelength sensitivity area.
Bruce
Could you use 2 pings and fire them at slightly different intervals then differentiate the readings? This may give finer detail than post #2 states.
Perhaps using a spectrum of light that the photosensitive film is not sensitive to also may provide a better measurement.
Is there anything directly behind the film?
I'm thinking maybe a sensor based on capacitance.
C.W.
http://gadgetgangster.com/find-a-project/56?projectnum=138
It appears to be on sale at the moment and you may be able to modify it to suit your needs.
Robert
I was thinking of the same thing earlier today. I wonder if those transducers could be driven at a high enough frequency to make a significant difference in its precision. I know piezo buzzers work best at certain frequencies but they will also work outside their optimal range but at lower volume. Maybe the ultrasound transducers could be driven at a higher freqency giving higher precision with a shorter range.
Bruce, assuming your film is not sensitive to infrared, an IR distance sensor like this one, might be your best bet:
-Phil
I thank you all for your support.
And for those that responded, it appears as though Phil has the closest solution.
@Phil
The spectral sensitivity graph for the film drops off the chart at approximately 715 nm, and the Sharp GP2Y0A21YK0F IR Sensor datasheet specifies a wavelength of 870 plus/minus 70 nm, so I assume it would work without giving me any grief. However I cannot find any information that specifies the accuracy of this sensor. Just how accurate are these sensors?
Bruce
Good to know. You probably just saved me a bunch of time because I was considering trying to drive one at other frequencies. I'd been thinking about it ever since the echocardiogram.
For "accuracy", you will probably have to calibrate it. For "precision" and "repeatability', it should be spot on, since I assume the target material and orientation will be the same every time. In any event, at only $11, testing it will be cheap.
-Phil
Thanks for the input, I definitely appreciate it.
Bruce
I don't think the GP2Y0A21YK0F will have resolution anywhere near what you want, I recall getting resolutions on the order of a 1/2 inch or so at best on a robot.
You might want to try to locate a GP2Y0AH01K0F high precision sensor, but even it only claims 0.1mm (~0.004 inch) resolution in the range of 4.5 to 6mm.
Here a a link to the PDF, but they don't stock the item:
http://media.digikey.com/pdf/Data%20Sheets/Sharp%20PDFs/GP2Y0AH01K0F.pdf
C.W.
This is a device we used to use to focus the Z-Axis on one of our Gerber Phottoplotters to determine the height above .004 film, .007 film, and glass plate.
http://www.massa.com/Datasheets/E-188-220%20Datasheet%20090922.pdf
Jim
Thanks for the link and the previous description of the aperture plate.
Bruce
I just wish I could find the 2-3 boxes of my Gerber documents so I could provide some supporting documentation, (schematics, etc).
Shouldn't take a month or so.
I use a comparator on the detector so that the sensitivity can be set. If you wish I could provide a schematic.
Those really look interesting - I would love to see the schematic. What is the maximum distance you've tried?
opps - ill provide a schematic soon. I am at "my main" office, ill be at my "home" office tonight.
Thanks for the input.
So I would imagine that these devices would be okay. As for the schematic, well I am always interested in seeing a nice little schematic for accomplishing a given task. As they say, "A picture is worth a thousand words".
Thanks again for the input Bits.
Bruce
J1 and J2 are for the laser and photo-transistor. U1 is used as a comparator, change the voltage that triggers by adjusting the pot. I attached LASER_SEN_A and LASER_SEN_B to i/o pins on the propeller.
Attachment not found.
Thank you very much for the schematic. I appreciate your effort and sharing.
Bruce
Thanks for the schematic.
Am I right in assuming that the laser is driven by 3.3V with a series resistor of 166 ohms (I don't see a symbol for the laser just the word laser)
Yes, J1 & J2 are used for the laser (pins 1 & 2) and the detector (pins 3 & 4). I specifically had to use 3.3V due to board real-estate and cost but, 5 volts would work as well. A resistor re-calculation would be needed however.
Most designs use a "foot" but I don't trust myself to build one with enough level of accuracy.