[Dprglist] Compass heading using gyroscopes?

Sun May 17 19:57:26 PDT 2020

Murray,
    I don't know what size gap you are trying to detect or the speed that
the gap may appear. Hhowever if the sampling rate is slow, about once per
second, another possibility is a laser distance meter with a serial port.
You can get a laser distance meter board with a serial port from Aliexpress
(I have seen them listed, but can't seem to find the right search terms, so
no link), or you might look at this project (
https://hackaday.com/2014/03/29/hacking-a-laser-tape-measure-in-3-easy-steps/).
I own one of these meters, have brought the serial port out, and played
with it. Its cool, but a robot generally needs a faster update rate.

Regards,
Doug P.

On Sun, May 17, 2020 at 9:41 PM Doug Paradis <paradug at gmail.com> wrote:

> Murray,
>      Benewake has a new LiDAR module called the TF-Luna. It has a range of
> between 0.2 to 8 meters and costs about $10 less. It has update frequency
> of 100 Hz, and 2 interfaces: 115200 serial, and I2C. It is available from
> DFRobot or Amazon. Here is the DFRobot link:
> https://www.dfrobot.com/product-1995.html. You also might be interested
> in some testing I did on the Benewake TF-mini for outdoors (See:
> https://www.youtube.com/watch?v=Mn-_0s5Rb1M).
>
> Regards,
> Doug P.
>
>
> On Sun, May 17, 2020 at 8:46 PM Murray Altheim via DPRGlist <
> dprglist at lists.dprg.org> wrote:
>
>> Hi David,
>>
>> This seemed timely as I was just putting in an order to Mouser for
>> a replacement Adafruit 240x240 TFT display (as Adafruit is still
>> discouraging ordering from them directly). While rewiring the
>> existing one over the weekend I somehow managed to somehow burn it
>> out. Grr. I broke a few things this weekend. Sometimes things go
>> awry [can you say "tits up" on a public forum?].
>>
>> I'd originally thought my existing VL53L1X ToF sensor might be able
>> to locate a gap at 8' (2.44m) but forgot that its field of view is
>> 27°. So no minding the gap there.
>>
>> My other thought on alignment was to use one of those TFMini wannabe
>> LiDARs with an "ideal" range of 12m and a 2.3° "signal acceptance
>> angle" (which may be the same thing as field of view, dunno). But
>> 2.3° at 8 feet is about 4 inches, which almost seems good enough.
>>
>> The TFMini is around NZ$80-90 and sucks up 800mA of juice, so it
>> wasn't my first choice. By comparison, the chunky Sharp GP2Y0A710K0F
>> IR sensor ranges up to 5m, uses only 30mA and is about 2/3 the price.
>> They don't mention in the specs its field of view but sure it's
>> pretty wide. For a different purpose, understood. And the TFMini
>> isn't actually a real LiDAR anyway, just a lens-focused LED. pffft
>>
>> I like the laser pointer idea better.
>>
>> I looked and the only laser pointers on Mouser's website are the
>> industrial ones (Class 3), the kind that burn holes through whatever
>> you're pointing them at -- I could tattoo my cat at 20 feet. I found
>> a more suitable one on the NZ equivalent of eBay (TradeMe) that is
>> meant to mount on top of a gun (of course). In the advertisement it
>> states:
>>
>>   "Plus, you'll be hitting meaningful targets, like bears and ducks
>>    and manly things, as opposed to the pretty little flowers that
>>    just happened to be in the way of your poorly aimed shot."
>>
>> I'm not sure what a meaningful target is, except that there are no
>> bears in New Zealand so the guy is plainly either out-of-country or
>> out-of-his-mind. But this seems like the right model, runs on three
>> AG10 batteries, so either 3.3V or 5V probably would be fine, and it
>> comes in tactical black. Very cool and menacing.
>>
>> This is *iff* I decide to partake in these silly contests. [he says
>> as he pulls out his credit card...]
>>
>> On 18/05/20 12:00 pm, David Anderson via DPRGlist wrote:
>> > Murray,
>> >
>> > Your comment is spot on.  On my SR04 robot there is a calibrated
>> > laser pointer for that very purpose; pointing the robot accurately
>> > at the first target.   For the experiments with the RCAT robot,
>> > the robot itself uses it's sonars to do the alignment, but since
>> > in the demo video there are no other waypoints, it's hard to know
>> > how effective it is.
>> >
>> > cheers
>> >
>> > dpa
>>
>> ...........................................................................
>> 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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>
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