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Crazy Arduino Automations Blog The WRONGCO Hamper Helper–blog 2-Intro to Optical sensors from a Dummy
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  • Author Author: robogary
  • Date Created: 6 May 2023 12:16 AM Date Created
  • Views 830 views
  • Likes 7 likes
  • Comments 1 comment
  • Arduino Day Challenge
  • crazyarduinoautomationch
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The WRONGCO Hamper Helper–blog 2-Intro to Optical sensors from a Dummy

robogary
robogary
6 May 2023

Please Reference Blog 1 for background info   The WRONGCO Hamper Helper - experiment 1 dirty clothes pile height detection - not so good 

Blog 2 is about my learning adventures and experiments to have optical "eye beam" interruption detection 

FIRST -  A 5MM Photo Transistor Phototransistor PT334-6C is selected to replace the VS1838 for dirty clothes height detection by a broken light beam.

Specs show the phototransistor best performance is with IR light.

It takes .5mW/cm2 to fire it at 1 mA and it maxes out at 3.5 mA. This part is confusing because another part of the spec says, Max Ic = 20mA, rated Ic=3.5mA.

Use a 1.5k resistor from 5v to collector.

image

Collector is the short leg/flat side. 

image

Test 1 - ‎Using an 100F5T-IR-FS- 940NM  IR LED as the light source,these LEDs have a forward voltage drop of 1.2 volts, and nominal 20 mA current. 

Used a 261 ohm resistor combo to feed the phototransistor from 5v, 14.5 mA (17mW)

Vdrop of the VS1838 1.5k resistor when IR LED directly aligned to VS1838, caused it to saturate. The Alignment cone was critical, no room for error. 3-4 inches separation quickly dropped Vresistor to .8V

Test 2 – Using an 8mm straw hat 100mA white LED, driven with with 57 mA (171mW) , was not effective. The beam width is too wide, hard to align to the phototransistor. It did yield better results than trial 1 to be a possible solution for an "electric eye" beam, but isnt good enough.

Trial 3 - Infrared IR 36 Led Board Plate for CCTV CCD Security Camera 12V 250mA . The intensity wasn’t high enough, didn’t work well for a close range target.

image

Trial 4 – Time for a monumental game-changer. Need a beam with some beam focus/reflector and a lot more light power.  I shopped for several varieties of tactical flashlights, but found an inexpensive gem of a flashlight.  

https://www.harborfreight.com/lighting/flashlights/144-lumen-ultra-bright-portable-led-worklightflashlight-63878.html   for only $1.79

image

Lumens to Watts calculator https://www.rapidtables.com/calc/light/lumen-to-watt-calculator.html  for LED lamps uses conversion 90 lm/watt

144 lumens is 1.6 Watts illumination, altho there are 2 LED sections, so expect the LED bar is really somewhat less power by itself.

Hacking the flashlight, it uses 3 AA batteries, a 3 way on switch with one position  to the HX-365A1 COB LED light bar with what looks like 8 LED spots. 

The COB LED consumes 1.3A at 4.0V  measured by powering with a MP710086 adjustable volts and current power supply.

The flashlight is rewired to bypass the manual switch and will be powered from a 5V source with a current limit resistor (or a Buck P.S. with adjustable current limit).

I’ll use a MOSFET or transistor to drive the LED from an Arduino.

 image

Future functional Improvement Steps (but not cost improvement steps) could include changing the photo transistor to a darlington photo transistor package, and/ or, an even brighter light source or COB strip.

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Top Comments

  • DAB
    DAB over 2 years ago +1
    Nice update. What you need is an odor detector.
  • DAB
    DAB over 2 years ago

    Nice update.

    What you need is an odor detector.

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