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“Coasterbot 2” contest with a robot using this
system (Figure 3) for navigation and targeting. Info
is available at www.jameco.com/Jameco/
2results.html and my video entry is at https://
www.youtube.com/watch ?v=dZTfIyrRne0. I
actually contacted Philo to thank him, and he was
happy to see his work inspired me several years later.
So, again, it’s a neat sensor which can be hacked
into a DIY laser sensor module with some effort.
In contrast, the new laser sensor shown in
Figure 4 comes ready to use. Figure 5 shows the
schematic. You can find more information on
Waveshare’s “Obstacle Detector” at
Laser_Sensor. It looked to me like an easily
sourced drop-in replacement for the
Hamamatsu sensor, even though it was only
listed as an obstacle detector.
I ordered three $10 sensors from
www.robotshop.com/en/obstacle-detection-laser-sensor.html and was
The datasheet specs a wide supply
voltage range from 2.5V- 5.0V and, in fact,
most of the onboard components are for
the PT1301 voltage boost circuitry for the
laser. Powered from 5V, the sensor draws
28 mA and the peak output voltage is
4.79V. Powered from 3.3V, I measured a 47
mA draw and peak output voltage of
3.17V, so this is a very user-friendly sensor.
The laser receiver is a clear three-pin
package which looks like a phototransistor or the
Hamamatsu sensor. Adjacent to the brass laser tube is a
similar-looking component which is apparently the laser
modulator. The datasheet lists the modulation frequency as
180 kHz. Seeking more information, I emailed Waveshare,
which is a Chinese company. Their reply:
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
So, there you have it! Straight from the manufacturer!
You can see my initial test video at https://www.
youtube.com/watch?v=5BTCoUflnEI. The module has
two red SMT LEDs: one for power on, and one indicating
detection of a reflected modulated laser signal. The output
signal is normally high/active low — much like a 38 kHz IR
receiver module. The removable lens is held on with double-sided tape, and is critical to achieve sensing distances over
~ 8 inches.
Closer than that, the lens interferes with proper
function due to beam alignment and parallax effects. Max
range is very dependent on the color and reflectivity of the
surface. Here are some results from my range tests:
• White surface max range 36”
• Black plastic computer case 12”- 18”
• Black resin watch strap 12”
• Dark brown fabric 8”
• Black fabric not detected
• Sunny outdoors, Scotchlite reflector 60+ FEET
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