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Author Topic: Anyone expermenting with JTs and has an Arduino  (Read 10776 times)

Legalizeshemp420

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Anyone expermenting with JTs and has an Arduino
« on: October 01, 2013, 01:25:16 PM »
BH1750FVI

Only around $2.65 and it is simply a LUX meter basically.  What you can do is use it to measure the brightness of your LED between your tweakings to see if you are getting more for less or not.

VERY valuable to have and really the only way to tell what is happening.
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TinselKoala

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Re: Anyone expermenting with JTs and has an Arduino
« Reply #1 on: October 01, 2013, 11:30:16 PM »
That's pretty cool, it eliminates a major calibration/conversion issue with the sensor I used. I'll have to get this thing you recommend and experiment with it. The sensor I used gives a frequency output that's proportional to the light intensity, so you need to convert that to some power/area measurement in the Arduino code. It sounds like this BH1750 unit gives its output in lux directly.
http://www.youtube.com/watch?v=1Kzf7S-pOEM
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Legalizeshemp420

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Re: Anyone expermenting with JTs and has an Arduino
« Reply #2 on: October 01, 2013, 11:47:42 PM »
It does and why I suggested it.  I am going to get the 2530, this, and I have the parts on order for the inductance meter.   I figure with that, and my 20mhz scope, I should be set.
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MileHigh

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Re: Anyone expermenting with JTs and has an Arduino
« Reply #3 on: October 01, 2013, 11:55:03 PM »
I think there may be lots of issues so I would be cautious. It's an ambient light sensor so it all depends what you are trying to accomplish.  Are you trying to gauge the subjective perceived brightness of the LED and ignore the fact that it is flashing?  Then it might be okay but there are still lots of catches.  How does the sensor deal with flashing?   What about its spectral response, etc?

I am not trying to spoil the party.  It may well be the data from the sensor is reasonably in line with the subjective perception of the brightness of the LED by a person.  In that sense you are fine.  On the other hand if you are trying to use the light output of the JT as an indication of its electrical efficiency then it may be more complicated than things seem.
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Legalizeshemp420

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Re: Anyone expermenting with JTs and has an Arduino
« Reply #4 on: October 02, 2013, 12:02:36 AM »
Quote from: MileHigh on October 01, 2013, 11:55:03 PM
I think there may be lots of issues so I would be cautious. It's an ambient light sensor so it all depends what you are trying to accomplish.  Are you trying to gauge the subjective perceived brightness of the LED and ignore the fact that it is flashing?  Then it might be okay but there are still lots of catches.  How does the sensor deal with flashing?   What about its spectral response, etc?

I am not trying to spoil the party.  It may well be the data from the sensor is reasonably in line with the subjective perception of the brightness of the LED by a person.  In that sense you are fine.  On the other hand if you are trying to use the light output of the JT as an indication of its electrical efficiency then it may be more complicated than things seem.
All I am doing is replacing an expensive LUX meter that people already use to test these and with a simple device, and an Arduino, you can do the same.  It is a LUX meter so it will do what a standalone LUX meter does in the same situation.

We already know that a standard LUX meter sees the flashes and doesn't care so I hope this doesn't either.

Basically it is just a way to compare the same LED flashing and what it says the LUX is then you change something in the JT and retest the same LED to see the difference in LUX.

So, not an Apples to Oranges comparison just Apples to Apples with the Apples having been washed or not, a bite removed from it or not, etc...
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MileHigh

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Re: Anyone expermenting with JTs and has an Arduino
« Reply #5 on: October 02, 2013, 12:15:23 AM »
Sorry to complicate matters.  I see that it's a LUX meter which is all about the human perception of brightness.  So it should work fine, I would just recommend doing some due diligence and test it at different flashing frequencies.  For example, you may perceive that an LED is the same brightness when flashing at 100 Hz or 12,000 Hz.  If the chip LUX meter shows you the same intensity also, then chances are you are in great shape.  Plus it must be fun to program and poll it with your Arduino.
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TinselKoala

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Re: Anyone expermenting with JTs and has an Arduino
« Reply #6 on: October 02, 2013, 12:19:05 AM »
Well, MH has a valid point about the sensor that I use, anyway. How does it handle integration of the LED pulses from the JT? That's why it needs to be calibrated against not only the same LED driven by known DC power, but also against some other reliable measure of light power. If it reads "x watts/cm" looking at a steady DC light power level, are we sure that a pulsed light at the same actual average power will still read the same "x watts/cm"?

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Legalizeshemp420

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Re: Anyone expermenting with JTs and has an Arduino
« Reply #7 on: October 02, 2013, 12:27:10 AM »
I agree.

What could be done is to set up the sensor in a tube with a LED on one end and the sensor on the other.  Now flash the LED and see what changes because something should change but will it change from 1k pulse and 12k pulses?  if the LUX doesn't change very much then it should be fine but if you were flashing 1hz then went to 1khz I expect the LUX to drastically change.
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MileHigh

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Re: Anyone expermenting with JTs and has an Arduino
« Reply #8 on: October 02, 2013, 12:31:37 AM »
For reference for the curious:

The lux (symbol: lx) is the SI unit of illuminance and luminous emittance, measuring luminous flux per unit area. It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watts per square metre, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception. In English, "lux" is used in both singular and plural.


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Legalizeshemp420

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Re: Anyone expermenting with JTs and has an Arduino
« Reply #9 on: October 02, 2013, 01:01:23 AM »
Lux is a measure of intensity that is weighted against the human eye’s sensitivity.  If you look around the web, and read the datasheet, you will see that irradiance is approximately 1uW/cm2 per khz using TinselKoala's TSL235R setup.
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