Ebay Laser & Sensor Tests FYI

erco

Just received lasers & two different sensors. Quick test results, FYI.


PCB lasers: 5pc/$2.75
3 pin connector:
-=ground
center=NC
S=+5V



$15 sensor, emits DC laser beam
Lens over phototransistor (you apply using mini foam tape pads)
3xAA cells
digital output, active low, very color dependent
1 red power LED
1 red sense LED
white surface max range ~36"
black plastic computer case/battery box ~12-18"
black resin watch strap ~12"
dark brown fabric ~8"
black fabric not detected



$1 analog sensor
1 red power LED
dark = 0V
output varies up to 4.12V when illuminated by red laser
get ~1V fluctuating from IR remote close/pointblank




BTW I received ten of these $3.72 Sharp IR sensors and the one I tested worked fine.
http://www.ebay.com/itm/262134861038

erco

Other than its $15 price, that first laser sensor would make an interesting line follower robot. More like an overhead camera, as opposed to most bots practically dragging their sensors on the ground. Shameful! But the laser is not modulated, so using more than one might be problematic. Could use one sensor and multiplex several lasers aimed a width apart. Or use one stock sensor and servo scan it back & forth across the line as the bot rolls forward.

Either way, one or more visible laser dots on the line are a win win.

Find me one person who doesn't like blinking LEDs and laser beams. I dare you. Even cats like lasers!

erco

There's much more to the $15 laser sensor than I initially thought after more research & testing. It's made by Waveshare, and there is some info at http://www.waveshare.com/wiki/Laser_Sensor . The Ebay listing I bought it from was titled: Laser Sensor Module Laser Transmitter Non-modulator Module, so I assumed presumed it used a steady DC laser signal. But the PDF at that website says its modulated at 180 kHz. Sounds high to me, but it must be modulated since it won't trigger from a simple laser pointer.

The schematic at http://www.waveshare.com/w/upload/9/98/Laser-Sensor-Schematic.pdf makes it look like the clear "phototransistor" adjacent to the brass laser tube is actually doing the modulating. Sorta makes sense.

There just ain't that much other circuitry on the board, there's a PT1301 5V booster (module can be powered from 2.5-5V) with coil, SS14 Schottky diode & passives. Also two J3Y transistors and two SMT LEDs & resistors.

Without the lens, that ~36" max working range goes down to ~8".

I tested it outdoors last night with some mediocre retroreflector material (as I used with the S6986) and it worked at an astounding 60-70 FEET! It may work nearly as well in the daylight with proper shielding from sunlight.

How did we live this long without this sensor? If you call that livin'...

Just get one and use standard laser good sense & eye protection. This may be the last erco-approved buy of 2016! Turns out they are available from many sources:

http://www.ebay.com/itm/251680140316
http://www.robotshop.com/en/obstacle-detection-laser-sensor.html
http://www.waveshare.com/Laser-Sensor.htm
https://www.aliexpress.com/item/Waveshare-Laser-Receiver-Module-Laser-Sensor-Module-Transmitter-Module-for-STM32-AVR-PIC/2042529584.html
https://www.amazon.com/Waveshare-Laser-Receiver-Sensor-Transmitter/dp/B00NJNYQ9G

erco

I just (h)ordered 3 more from Robot Shop (yeah, I know, Duane). $33 shipped.

A laser-guided BoeBot must be built over Christmas break!

erco

Test video. Likey-likey!

Publison

Other thread deleted as requested.

erco

Per xanadu's request in the deleted thread, I did a quickie outdoor range test today and got over 50 feet! Very sunny ~12:30, I put the beeping sensor breadboard from the video in an 8" cube cardboard box for a bit of daylight shielding. Set that on the sidewalk, horizontal beam. Then I took a similar sized box and put that same small piece of Scotchlite inside it and started walking down the sidewalk. Could not believe the range. I'm sure it is more than 50 feet, but there were a few factors working against me. The wind was wiggling the laser emitter, which wiggles the beam. And I'm looking into the not-very-dark-box, trying to see the laser dot and move the reflector onto it and listen for the beep to stop. It was operating 100% (not marginal at all) as long as I could see the beam. But I was getting sunblind out there and called it quits. When I have more time I'll do a more comprehensive test and accurately measure the distance. Outlook is good!

xanadu

Nice, thanks. This would make a good sensor for our race gate.

erco

Yes, it would make a fine break-beam detector as long as it's stably mounted, and if your drones are the right altitude to break the beam.

macrobeak

I have had a look at the Waveshare laser sensor module.
As per erco's tests, it has an impressive sensing range, and would make a good black line follower.
It is not much good for object detection because it black and soft objects do not reflect the laser beam very well.
I covered the module's laser with double sided tape and did some experiments with an external red laser;
- The lower bound of modulation for detection is about 18kHz. There is no upper bound. The datasheet claims a modulated beam of 180kHz (maybe they mean 18kHz? ? ?)
- If the external laser is pulsed or modulated the digital output at the detection data pin is nice and clean and the module can probably be used as a remote controller or for data transmission. At a modulation of 50kHz, it transmitted a 1200Hz pulse stream quite cleanly. I did not try any actual data transmission.

erco

Thanks for digging deeper, macrobeak! Very helpful info you have shared. I have 4 of these units now. When I get a minute, my next test is whether two or three units can operate together without interference. I can follow a line with one sensor (just look at one edge) but 3 sensors would allow faster motion.

Keep up your fine work!

Publison

What is the vertical component,(clear), next the the laser module? I almost looks like another sensor.

erco

Good eye, Jim! It looks just like the sensor, even same pink paint stripe. I emailed waveshare and this reply, where they call it a "modulation tube".

Hello,dear
your question: ". The laser modulation is actually 180 kHz? And what does the extra phototransistor near the brass laser do?"
our engineer said: That is the Modulated Tubes, which is modulated the laser as a regulated rate and send ,there is a receiving tube under the lens, which is used for receiving the fixed rate

Best I can tell, that phototransistor-looking component on the PCB by the brass laser tube is in series with the laser diode and modulates the output for detection by a similar companion receiver. Q1 on the attached schematic. The send/receive circuitry is quite minimal. Most of the components on the sensor board are for a PT1301-based 5V booster to run the sensor from as little as 2.5V. Propeller and 3.3V users, rejoice!

Schematics and "user manual" attached. From http://www.waveshare.com/wiki/Laser_Sensor

So why hasn't anyone except macrobeak bought these yet? It's Christmas! Stuff your stocking!

AFAIK Robotshop is still cheapest at $9.99 (plus shipping, ugh!)

Publison

Same old Chinglish. I thought it might be an ambient light sensor.

And what is shockwave? My favorite Shockwave is:



Got to see and touch at two Nashville Airshows.

MikeDYur

Hello,dear
your question: 

Friendly aren't they, of course you may be a frequent customer.

Publison

erco wrote: »

So why hasn't anyone except macrobeak bought these yet? It's Christmas! Stuff your stocking!

[/url] (plus shipping, ugh!)

Ordered one from Amazon. $15.99 free ship.

erco

A (Laser) Christmas Story:

No, Jim, you'll shoot your eye out! Ho, ho ho!

erco

SERVO magazine has declassified my article on the laser sensor, so it's fully available without a subscription. Best of all, no cookies!

http://www.servomagazine.com/index.php/magazine/article/April2017_MrRoboto

xanadu

Great article, "dear"!

I love that BS2 laser scanner.

erco

xanadu wrote: »

I love that BS2 laser scanner.

XLNT. Plenty of Stamp love in that article. The DVD-chassis robot shown in figure 3 is BS-2E powered.

MikeDYur

Great stuff erco, it takes quite a lot of material to come up with monthly magazine article. I also like the BS2 laser scanner, any ideas for a poor man's LiDAR?

erco

Tell me about it. Jonnymac warned me long ago how much time a regular column takes and how the monthly deadlines seem to come faster & faster. When I get desperate I'll ask you guys to lob me some easy questions about plywood, relays, BASIC, & Fahnestock clips.

WRT Lidar, that laser sensor can't measure range. Just whether it sees a reflection or not, which is very dependent on the object and color. Parallax's PING-dar project remains a favorite of mine. A worthy improvement would be to combine a PING ultrasonic rangefinder with a Sharp IR rangefinder in a similar scanning arrangement to combine sensor strengths.

MikeDYur

Anybody have experience with Solid State LiDAR?

Wonder if the price is right, cheap.

Pages are to big for me to browse.

http://leddartech.com

LEDDAR BENEFITS FOR DRONES AND UAV

Highly accurate, stable measurements
Wide field-of-view and rich spatial awareness
Enabling up to 360° obstacle and surface detection
Rapid data acquisition time of up to 140 Hz
Reliable operation indoors and outdoors
Immune to light, noise, vibrations, and wind

Whit

Great stuff Mr. Roboto!

macrobeak

MikeDYur,
Thanks for the link;
http://leddartech.com
Very impressive lidar modules of various complexities.
All sub $1000, some sub $500.
All have 5V power supply and 3.3v UART, so Prop interfacing should be straightforward.
I look forward to seeing some really interesting applications from these modules.

MikeDYur

Sparkfun is carrying this affordable unit by a respectable name.

https://www.sparkfun.com/products/14032

https://buy.garmin.com/en-US/US/p/557294

banjo

MikeDYur wrote: »

Sparkfun is carrying this affordable unit by a respectable name.

https://www.sparkfun.com/products/14032

https://buy.garmin.com/en-US/US/p/557294

Yeah, I actually hoarded this a month ago when I was in US to save some shipping and customs fees. Have hooked it up and secured it's working alright, now it's just waiting for a suitable project...

Heater.

Has anyone experimented with LEDar? Like LiDar but done with LEDs.
https://en.wikipedia.org/wiki/Leddar

Last year I saw a demo of LEDar by Leddartech. http://leddartech.com/modules/m16-multi-element-sensor-module/ A tiny dev kit that could detect objects out to some meters and provide 16 channels across the width of view. No moving parts.

I thought, Hmm.. can't we do that with a Propeller? ...

MikeDYur

Heater. wrote: »

I thought, Hmm.. can't we do that with a Propeller? ...

I'm downloading the datasheet now.

Till you mentioned LEDs, I didn't know how it was done. I bet it's doable.

MikeDYur

Hold on, optics are going to be less doable.

MikeDYur

May just be one element. This looks like the less expensive model.