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1  Using Arduino / Sensors / Light sensor being overwhelmed, suggestions? on: April 04, 2013, 01:45:50 am
I'm currently working on a project that involves light sensing.  Specifically detecting when an led blinks from appoximatly 2-5mm away. Only problem is there is a clear case between the led and my sensor and the project will be in outside in nearly direct sunlight.  I've reduced the ambient light as much as physically possible but it is still fairly high.   i.e.

 LED   <3mm>    Sensor
  =D |clear case| D=

My first approach was to use two cds photocells (one facing directly towards the led, and the other offset slightly) and a comparator circuit to detect when the led flashes. That didn't work because the photocells would be "washed out" by the sunlight and could not sense the led.  So, I've been searching digikey for a different sensor to suit my needs,  one that would be sensitive to the 630nm-ish wavelength of the led but still have range to detect changes in a high lux environment.  So far All of the sensors I've tried haven't worked out. Looking through various forums hasn't been much help either,  most solutions I've read involve reducing the ambient light in some way.  I was wondering if anyone could suggest a sensor that might work or perhaps a different approach that may be successful. 

Thank you for any suggestions.
2  Using Arduino / Sensors / Re: question on MPL3115A2 altitude sensor offset register on: February 06, 2013, 11:27:29 am
Ah yes, reading through the bitwise operators on the arduino reference page and your suggestion makes sense.  Thank you very much for the help and I apologize for such a newbie question.
3  Using Arduino / Sensors / question on MPL3115A2 altitude sensor offset register on: February 06, 2013, 10:31:35 am
I'm using a MPL3115A2 sensor from sparkfun.
-product page :
-Data Sheet

Unfortunately i'm new to programming and am having a bit of trouble  smiley-sad

I have the sensor set in altimeter mode and seems to be working properly so far.  I'm having trouble with the pressure offset feature.  From the data sheet I understand that sending the current ground level in Pa (divided by 2) to the 0x14 and 0x15 addresses would set the ground level for a relative altitude measurement.  My project also incorporates multiple bmp085 sensor, so no problem.  When on the ground I read the bmp085 sensor and get ground level pressure in Pa, then send that value to the MPL3115A2. Unfortunately I'm unsure how to send my Pa 'int' value in hex to the sensor.
groundPressure = value_from_bmp085
groundPressure *= .5;

value_to_send_x14 = Magic_pixie_dust(groundPressure);
value_to_Send_x15 = More_magic_pixie_dust(groundPressure);

// BAR_IN_MSB (0x14):
  IIC_Write(0x14, ???? );

  // BAR_IN_LSB (0x15):
  IIC_Write(0x15, ???? );

Any help would be greatly appreciated.
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