PaulHolland said:polymath, Your calculations make one fatal error and that is: emmitted light from an LED is NOT lineare with current !!!!.. two times the current does not give two times the light emmitted from the LED. If this was true they would simply use PWM to make superled's !!.
The second error you make is that you think your light emmission is 416% up but you forget to take the 1/10 emmision time into account. since 9/10 there is no light your total light emmision is = 7.5 * 1/10 = 0.75 about 50% of what you get with constant current.
Paul.
x10 current will produce x10 output - LinearThe intensity of NSPR346BS(Red) is a linear function of current
Dave_UK did not mention white LEDs in the start of the thread.The intensity of NSCW215(White) is not a linear function of current
PaulHolland said:polymath,
A transistor also has a linear region and a saturated region when its relationship between input and output is nolonger linear. Power amplifiers for FM make use of this region for high efficiency (transistor looks like a switch in this mode). Your IR link makes the same use of this region by using frequency modulation, if you would use AM modulation you would not be able to get the same distance.
h**p://www.automotivedesignline.com/howto/190303172;jsessionid=K2L0WO2ZVI35AQSNDLQCKH0CJUNN2JVN
The human eye is integrating light it is seeing so a pulsed light source on/off for 50% will be half that of 100% etc..
to be short: a LED has an linear region followed by a non linear region close to the point of saturation.
Paul.
confirms the fact that if the human eye is provided with a short 500% 'bright' pulse for 50% time will integrate this pulse over the repetition period and conclude it is 250% 'bright' - just what I was saying - thanks.The human eye is integrating light it is seeing so a pulsed light source on/off for 50% will be half that of 100% etc..
I notice you have avoided making any comment about:polymath, Your calculations make one fatal error and that is: emmitted light from an LED is NOT lineare with current !!!!..
Contrast the steep voltage/intensity curve with the linear
relationship between current and intensity in Insert 1.
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