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boblai2010
03-28-2010, 10:37 PM
TSL230R Just can output the frequency·by the light change how can i set the frequency to the lux
My program is a basic stamp program and i just copy from the data sheet but i don't know how to change the frequency to the luxhttp://forums.parallax.com/images/smilies/confused.gif http://forums.parallax.com/images/smilies/confused.gif http://forums.parallax.com/images/smilies/confused.gif

Franklin
03-29-2010, 01:09 AM
You will probably need to calibrate the sensor to lux and for that you will need to borrow a meter that reads lux. Perhaps someone here has already done that and can help but I've not used that sensor.

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- Stephen

boblai2010
03-29-2010, 01:31 PM
ALso here i have a more question because i here listen some people said that photoresistor can measure lux but when i used it The RCtime is not output stable ,how can i make it more stable

Tracy Allen
03-29-2010, 11:09 PM
Instability in RCTIME usually means that wires leading to the sensor or other parts of the circuit are too long and are picking up AC noise. Also, if your sensor is looking at an artificial light source powered by AC mains, the readings will actually bounce around due to pulsations of light at twice the line frequency. (120 Hz).

One way to calibrate approximately is to put your sensor 1 meter from a 100 watt standard bare light bulb, or 1 meter from the center of the beam of a 50 watt R20 track-light bulb. That gives in the neighborhood of 400-500 lux. Outdoor full sunlight is in the neighborhood of 100000 lux.

Remember that lux is a photometric quantity that measures how well human eyes can see things, and defines a peak in yellow-green light at 555 nanometers. The sensors you have measure over a much wider range of wavelengths than eyes can see. That TSL230 would give a reading even under an invisible IR LED. Sensors for lux usually have a filter that cuts out the non-visible wavelengths and peaks follows the so-called photoptic curve of the eye's sensitivity.

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Tracy Allen
www.emesystems.com (http://www.emesystems.com)