Shop OBEX P1 Docs P2 Docs Learn Events
measuring small light intensity - around 0.01 lux — Parallax Forums

measuring small light intensity - around 0.01 lux

FairuzFairuz Posts: 12
edited 2007-09-06 03:43 in BASIC Stamp
Hie..

Is there any design by using Basic Stamp that uses sensor that capable of measuring light intensity around 0.01lux? I'm using this circuit to measure the level of backscattering light by using fiber optic cable.

Thank You

Comments

  • BeanBean Posts: 8,129
    edited 2007-09-05 01:22
    The TAOS TSL230 is worth a try.
    According to the datasheet it can measure down to 0.001 uWatt/cm^2

    Bean.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    The first rule to being successful is "Learn from your mistakes",
    The second rule is "Be willing to make mistakes"
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    www.hittconsulting.com
    ·
  • FairuzFairuz Posts: 12
    edited 2007-09-05 01:45
    Bean.. thanks for the reply. I have tried the sensor. However, the difficulties that I encounter is that when i interconnect it with basci stamp, it will leads to a very long waiting time before basic stamp able to produce the output if the light intensity is that small.
  • FranklinFranklin Posts: 4,747
    edited 2007-09-05 02:29
    How many lux is a uWatt/cm^2? (or viceversa)

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • KatyBriKatyBri Posts: 171
    edited 2007-09-05 03:48
    Here is some additional info you may find useful-

    http://www.parallax.com/dl/docs/prod/compshop/tsl230.pdf
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2007-09-05 06:20
    The conversion between lux and µW/cm2 depends on the color of the light. For green light at 555nm (the peak of the human color response),

    ·····1 lux = 1 lumen/m2 = 1.464mW/m2 = 1464µW/m2 = .1464µW/cm2

    So 0.01 lux = .001464µW/cm2. This amount of light, by the way, is equivalent to what you'd get from a quarter moon. It's not much.*

    TAOS has a high-sensitivity light-to-voltage sensor, the TSL257, that touts a 1.58V/(µW/cm2) response. For green light at 0.01 lux, this would put you in the millivolt range, barely above the '257's 200µV RMS noise floor.

    Another option is the TSL237 light-to-frequency sensor, which has a somewhat higher sensitivity than the TSL230.

    In any event, I'd give TAOS a call (972-673-0759) to see if they have any suggestions.

    -Phil

    *Ref: en.wikipedia.org/wiki/Lux

    Post Edited (Phil Pilgrim (PhiPi)) : 9/5/2007 6:25:35 AM GMT
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2007-09-05 17:54
    I've had success with the LX1973A from Microsemi, measuring twilight and moonlight levels to relate to activities of nocturnal animals. The sensor uses fourth root analog compression to enable it to cover from 0.001 lux up to 500 lux. That 6 orders range is great, but it does make calibration more problematic. The response is relatively slow at low light levels, in case that matters. The spectral response is tailored to the human eye model. The Stamp interface requires an ADC.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tracy Allen
    www.emesystems.com
  • FairuzFairuz Posts: 12
    edited 2007-09-06 03:13
    May I know the price of LX1973A. It surely fullfilling my requirement. Thanks
  • FranklinFranklin Posts: 4,747
    edited 2007-09-06 03:24
    www.digikey.com/scripts/us/dksus.dll

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2007-09-06 03:32
    They're around $5 (from Digikey as Franklin pointed out). It is in an MSOP surface mount package. I have msop to dip adapters and also the chips; if you need one contact me in PM.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tracy Allen
    www.emesystems.com
  • FranklinFranklin Posts: 4,747
    edited 2007-09-06 03:43
    Hey, sorry about that link. I clicked on it and it went nowhere like where I was. Like Tracy says $5 range.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
Sign In or Register to comment.