Time of Flight (ToF) VL53L5CX - 8x8 pixel sensor

@inq $25? I am sure I saw a little over $6 somewhere.

Posted by: @zander

@davee Narrow band filters can reject all but 3 to 5 nm of the spectrum. Finding one in the frequency of the laser being used is the challenge

 

Unfortunately, I don't think a filter will help... it is because the bad lighting (sun, incandescent, halogen...) is emitting light in that range already.  I don't see how you can filter out the same wavelength light based on its source... sensor's laser good - sun bad.  😎 

@inq If snow were not a problem, then the big bins of heated (by steam pipe) sand would not be needed. Wet leaves were also a problem.

https://en.wikipedia.org/wiki/Sandbox_(locomotive)

Posted by: @inq

Posted by: @will

What happens if you simulate that ? Suppose you hack together a case with a lid on a hinge, put the sensor in the box and run it until the readings stabilize and then open the lid to see how long it takes to stabilize again. That might stop from "remembering" a previous state.

A more serious answer, this time... I don't think the box idea will work.  It's opposite... anything close (being in the box) sets at the very next 15 Hz cycle.  Opening the box from that state to a 4+ meter scan would have this hesitation.

Thanks for the information, just another nail in this sensor's coffin (for me at least).

Posted by: @davee

I tend to agree that the sensor looks useful, as an improvement on the basic ultrasound sensor or similar.

I hope it didn't sound like I was presenting a silver bullet.  If it ends up only as a way to replace a phalanx of ultrasonic sensors (or servo scanning one) for obstacle avoidance, I will be mildly disappointed.  If it can be used to mapping, I will be pleasantly surprised and happy with the purchase and time spent studying it.  

The fact that bad lighting affects it so badly is disappointing.  But... ultrasonics have their limitations also.  So... its a tradeoff.

Its all big fun, just dink'n around with electronics/software though.

VBR,

Inq

Posted by: @robotbuilder

@davee 

Could it distinguish enough data to recognise its location in a 'familiar' area? ... I don't know.

Well that is up to @inq who has the sensor to experiment with.

I can think of experiments I would do with it.

I believe that the data is good enough to map a room.  Caveat - In good lighting (LED, Fluorescent).  At distances, I might have to play head games (delays) on the 15Hz readings.  

BUT... I haven't really scratched the surface of this sensor yet.  I'm betting the extra data/pixel can tell me that "pixel" is not valid... or is in one of these delays.  Also, @davee observations of playing with the sharpness.  There is also a bunch of stuff on integration time, I haven't even perused.  It just takes more time... integration time... and me digging out enough time to play with it.

VBR,

Inq

Posted by: @zander

@davee Did not know Sodium had any IR, that may explain the result. Yes, you are likely correct, at that cost the IR filter will not match a $500 astro filter.

I'm not sure that Sodium does either.  That was might gut reflex at the end of the first day.  It resembled the same behavior as the halogen bulb.  But, the second day, I admitted I was in error... that it was happening at the 4+ meter distance (and has the same apparent behavior as the halogen bulb).  

@inq As it turns out the sensor already has an IR filter and that model does NOT have the ambient light box checked in the product description, only 1 of the 7 TOF modules has ambient light checked (not sure what that means). I saw a demo of the unit and I don't get it. A 64 pixel camera vs even a 2,000,000 pixel camera seems to be a huge hill to climb.

If you think the laser is critical, then get an esp32 type camera module or raspberry Pi camera (same thing?) WITH NO IR FILTER* and a laser that will give you about 2^15 times more data points. Red laser pointers in various frequencies are readily available, an astronomy store can sell you a small piece of plastic to reduce the red laser to IR only and they may also sell the laser. I would be wary of lasers from other sources.

OR remind me why CV and a normal camera can't do a better job?

I hope I am helping but if not just tell me to take a hike, I am certainly not knowledgeable re this specific sensor but I am familiar with the photo/astro fields.

*IR FILTER on a photography lens is BLOCKING the IR, on a telescope or your TOF sensor it is blocking a certain % of ALL the light EXCEPT IR.

Posted by: @davee

So far, I haven't got involved with robots either ... though some, including @Inq's recent creations look really fun.... how does he get the time and skill?

I'll sleep when I'm dead.  Lot's of insomnia... enjoying my retirement.  But now I'm volunteering to tutor a special student and I'm doing that Ralf project for the library user's group.   It's slowing me up on this one.  

@inq I am fairly sure the max range is only 400CM/4M, what spec is telling you otherwise?

Posted by: @davee

I don't know about Inq's financial position, but since I am paying with my own money, I think twice before spending the equivalent of $20.

I'm ok in the sub $100 range for parts, but my group here is far more price sensitive, so me introducing a spinning lidar is simply insulting to them... so I look for cheaper alternatives (like this sensor) and hope to substitute some creative programming/mechanisms to compensate and get a near equivalent result.

Posted by: @davee

It might mean @Inq has to move his beer to a small nearby fridge for his bot to be able to find it, but that seems a 'small' price to pay, at least until the next generation of Inq-lings, with the next generation of sensors became available.   (Only a suggestion, Inq!!!)

Maybe, I just need a keg, a pump, a button and a tube.  🤣 

Posted by: @davee

I am however, always keen to find how things work ... and Lidar is one of those things I have never properly understood, beyond the most basic level of fire a laser and look for a reflection. However, it 'pops up' in a number of guises .. and is 'competitive' with other Time of Flight technologies.

I hope that by looking at and describing things to people, it encourages at least a few to look beyond the obvious and create something original.

And I am hoping Inq will persevere with either this is or a comparable device.

Always good to discuss ideas. Best wishes, Dave

Well... that avalanche dissertation (still to be studied) is far beyond my level of knowledge.  You may not have the hands-on, but it sounds like you have a lot of analytical background that is applicable and brings things to the table address problems.

I'll persevere... 

Posted by: @robotbuilder

I can think of experiments I would do with it.

Bring them on... If I can, I'll try it.

Posted by: @zander

@inq $25? I am sure I saw a little over $6 somewhere.

I think $6 is for just the little rice-grain-sized sensor itself.  I don't know how to wave solder (or whatever its called) and I couldn't see the little contacts on the back to do it anyway.  Therefore, I bend over and take it so I can have a break-out board.