[Dprglist] Fwd: PAA5100JE Near Optical Flow SPI Breakout is now available at Pimoroni!
Kevin T. Shin
sundance14 at gmail.com
Wed Jun 9 09:16:53 PDT 2021
Hi Murray,
I have been very interested in the optical flow sensors to detect the wheel slippage. I have used the old laser mouse, but certainly give this a try. Thank you.
Kevin
Sent from my iPhone
> On Jun 9, 2021, at 3:53 AM, Murray Altheim via DPRGlist <dprglist at lists.dprg.org> wrote:
>
> Hi Karim,
>
> I'll be very interested in hearing how you and yours figure out the best way to
> use these new sensors. I think overall they'll be very helpful to those wanting
> some sort of optical odometry, or at least some kind of optical assist. As I
> mentioned, even if it can't be used for truly accurate odometry over varied
> surfaces it still might be very handy for driving in a straight line, or other
> tricks we haven't even thought of yet.
>
> Cheers,
>
> Murray
>
>> On 9/06/21 9:34 am, Iron Reign wrote:
>> Thanks Murray. Very helpful. I've ordered a brace of them. They're not in the Amazon store yet, so gotta wait on international shipping.
>> On Tue, Jun 8, 2021 at 4:18 PM Murray Altheim via DPRGlist <dprglist at lists.dprg.org <mailto:dprglist at lists.dprg.org>> wrote:
>> Hi Karim,
>> I'll try to get the post, which is about half ready, posted ASAP, though I've
>> got a lot going on right now at home and work.
>> I think it's definitely worth a look. My initial play with it was using the
>> existing PMW3901 Python library, as suggested by the Pimoroni techs, and I'd
>> tested it out over nine different surfaces and with that library I found the
>> image complexity was clearly related to the measured velocity, but Pimoroni
>> updated their library, and while the update doesn't entirely eliminate that
>> issue, it's much less significant than before. I don't think you'll be able
>> to use the sensor solely to measure distance over significantly varied
>> surfaces with accuracy, but over a relatively constant surface I think it's
>> pretty good, within a few percent.
>> It outputs a simple stream of x,y values when moving, clearly on an interrupt
>> basis as that stream stops when the movement stops. I measured the 'x'
>> dimension (oriented as it was) over one meter and so long as I stayed on the
>> kind of surface that I calibrated it for the measurements were quite accurate.
>> An interesting notion might be to use the other axis with a PID controller to
>> travel in a straight line, as while dragging my little robot sled over the
>> test surface I'd get small 'y' values that could be used for course correction.
>> With the new Python library I think the minimum to maximum of the nine
>> surfaces I tested on (tile, wood floor, lawn, concrete, rug, etc.) varied by
>> something like 10-15%, but on any given surface the ten runs of my test
>> varied by only a few percent max, often less than 1%. Repeatable results.
>> It'd be possible to calibrate the sensor over different surfaces and switch
>> calibrations based on the surface if it were possible to detect the surface
>> type, possibly using a camera or spectrometer sensor like the Pimoroni
>> AS7262 that could detect color (which actually works pretty well, e.g.,
>> it's easy in my house to know the difference between my tile, wood and
>> carpet flooring by color). I've got a spreadsheet of results that will be
>> part of the review/blog post.
>> At £18.90 (US$26.75 / NZ$37) it's not cheap but I think worth a look, yes.
>> The only downside really, which was entirely predictable, is that its
>> operating range is 10-35mm, suitable for hanging underneath a small robot,
>> but not so much under say, a Mars rover, whose bottom is likely higher than
>> 35mm. In that case the PWM3901 would be more suitable, but not necessarily
>> as accurate,
>> Cheers,
>> Murray
>> On 9/06/21 8:52 am, Karim Virani wrote:
>> > How about at least a teaser? Worth a look?
>> >
>> > On Tue, Jun 8, 2021 at 3:49 PM Murray Altheim via DPRGlist <dprglist at lists.dprg.org <mailto:dprglist at lists.dprg.org> <mailto:dprglist at lists.dprg.org <mailto:dprglist at lists.dprg.org>>> wrote:
>> >
>> > Hi,
>> >
>> > FYI, Pimoroni has finally announced stock availability on their new PAA5100JE
>> > Near Optical Flow Sensor, which I'll be posting a review on hopefully soon.
>> >
>> > PAA5100JE Near Optical Flow SPI Breakout
>> > Detect motion of close-up surfaces with this Breakout Garden compatible
>> > optical navigation breakout - great for floor tracking for ground dwelling robots!
>> > https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout <https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout> <https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout
>> <https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout>>
>> ...........................................................................
>> Murray Altheim <murray18 at altheim dot com> = = ===
>> http://www.altheim.com/murray/ <http://www.altheim.com/murray/> === ===
>> = = ===
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>> Rustle in the autumn wind
>> That blows through my reed hut.
>> -- Minamoto no Tsunenobu
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> --
>
> ...........................................................................
> Murray Altheim <murray18 at altheim dot com> = = ===
> http://www.altheim.com/murray/ === ===
> = = ===
> In the evening
> The rice leaves in the garden
> Rustle in the autumn wind
> That blows through my reed hut.
> -- Minamoto no Tsunenobu
>
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