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Author Topic: Finally! Cheap TOF Laser Rangefinders are here :)  (Read 1632 times)

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Offline weatherc

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #15 on: April 01, 2018, 07:41:35 PM »
I guess a snow sensor that only measures overnight is probably still worthwhile considering the very low cost? At least it would show daily totals...

At least up here north at 60N where daytime (sunrise-set) are only 6h as shortest, and the weather mainly cloudy during winter, should dark-time measuring work quite well i think. Of course, it wouldn't be fully realtime-measuring during daytime but would give at least "morning" and "evening"-values.
Using RPi and ie solarsensor-data from the weather-station can this probably even be tweaked like "if solar == 0 then measure" or just use the sunrise/set-times with possible offsets using PHP. I got mine into test just some days ago so i haven't data from the dark part of the winter.

Offline MichaelPT

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #16 on: April 02, 2018, 02:50:37 PM »
It's the same sensor component so it's no surprise that I confirm weatherc's results. Styrofoam sheet in bright shade is fine, but in full sun results in an FF error value in the serial data. Not unexpected from such a tiny micropower laser.

I guess a snow sensor that only measures overnight is probably still worthwhile considering the very low cost? At least it would show daily totals...

Hi
this is probably going to be a silly suggestion, have you tried putting a sunglasses lens that are mainly clear then as the sun get brighter they go darker
some kind of reactive plastic lens

Just wondering if the laser sensor will go through such a thing but could help eliminate the bright light
mick

Offline niko

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #17 on: April 02, 2018, 06:38:32 PM »
Just wondering if the laser sensor will go through such a thing but could help eliminate the bright light
mick

The reflected solar radiation from a white target is many, many times stronger than the reflected signal from the tiny micropower laser. (When you receive yours you will see just how tiny it is.) Anything we do to optically reduce the reflection will also reduce the laser reflection so it doesn't change the situation, and it has to be out in the open otherwise the snow will be obstructed. Short of automating a sunshade when taking a measurement I don't see any way out of this one  :(

Offline mcrossley

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #18 on: April 02, 2018, 06:50:16 PM »
Sounds like a job for a narrow bandpass filter - if you can find one at the correct frequency.
Mark

Offline niko

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #19 on: April 02, 2018, 07:20:26 PM »
Agreed, the chip has one already, and one hopes the laser signal is modulated to separate it from the "DC" sunlight. However it's a 940 nm laser and there's a LOT of IR energy in sunlight at that wavelength  :(
« Last Edit: April 02, 2018, 07:22:08 PM by niko »

Offline mcrossley

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #20 on: April 02, 2018, 08:07:29 PM »
I suspect the inbuilt filter isn't very narrow or even a low pass, a good narrow band interference filter tends to be a bit pricey - going by my astro imaging experience. Though I guess the filter they use will be tiny.
Mark

Offline weatherc

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #21 on: April 02, 2018, 08:29:56 PM »
It doesn't need direct sunlight to show off.
During cloudy weather + resonable snowfall today did it show off whole day too.
Shade made with a piece of cardboard all the way from the sensor to the snow during sunshine do not help either.
From my and one other finnish tester tests have we figured out it shows correct from ca 30 min after sunset to ca 30 min before sunrise.
Once it gets lighter do it start to slowly rise the value until its close to 2 m. In the evening when it gets darker the oher way, it slowly drops the value until its correct.

On the good side, it measured correct todays new snow amount of ca 10 cm once it got dark. The values made with avergae of 15 readings are quite stable too (inside maybe 0.5 cm or so).
« Last Edit: April 02, 2018, 08:31:44 PM by weatherc »

Offline niko

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #22 on: April 02, 2018, 09:54:29 PM »
The datasheet admits that the outdoor performance is quite limited, max range is reduced to 50%. The outdoor test condition is:

"Outdoor overcast corresponds to a parasitic noise of 10kcps/SPAD for VL53L0X module. For reference, this corresponds to a 1.2W/m at 940nm, and is equivalent to 5k Lux daylight, while ranging on a grey 17% chart at 40cm"

I don't think in Lux and don't have a meter so I have no idea how light or dark that is :dontknow:



Online Weather Display

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #23 on: April 02, 2018, 10:17:09 PM »
multiply lux by 0.0079 to get wm/2 rough estimate

Offline niko

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #24 on: April 02, 2018, 10:35:42 PM »
39.5 W/m2  - pretty shady.

Thanks.

Offline weatherc

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #25 on: April 03, 2018, 11:20:10 AM »
39.5 W/m2  - pretty shady.

Thanks.

Here it starts to work properly at 0w/m2.
Attached roadcam-pic some 5 km away, to give a glue about how dark/light it is at that point, is from 45 min before sunrise.

Offline MichaelPT

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Re: Finally! Cheap TOF Laser Rangefinders are here :)
« Reply #26 on: May 01, 2018, 08:34:41 PM »
Hi

Just an update on my progress
please see images of the laser Control board

Circuit board design based on diagram from Niko Pic programme

I'm currently doing some tests , will update my website on how to make the circuit board and how to put the  project together ,this was only possible with the help of Niko

thank you
mick

 

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