In this post i will compare the new ambient light sensor that i got - the TEMD 6200FX01 by Vishay to the TEMT 6000 phototransistor [PT]. The TEMD6200FX01 is a PIN photodiode [PD]. More information can be found in its datasheet here. The circuit i hooked up with the PD is shown below.
The PD is reverse biased with a voltage of 3.3V and the output is taken across the 10K load resistor. Looking at the reverse voltage vs capacitance curve from the data sheet i approximated that the diode capacitance will be around 30 pF. The load resistor and the capacitance will determine the cut-off frequency and the time constant. Based on above values these turn out to be as shown below
Hence the cut-off frequency happens to be approximately around 530 KHz with this configuration of the PD.
The LED was modulated with different frequencies and the light was focused on both the PD and the PT. The below waveforms were observed on the scope. The orange trace is the PT output and the blue trace is the PD output. (In case of the PT the circuit is same as before and the output is obtained across a 10K resistor). It was pointless to go beyond 10KHz as the PT output faded away.
100 Hz square wave
1 KHz square wave
10 KHz square wave
The board i designed for mounting the TEMD 6200 0805 SMD so that i could breadboard the test circuit
In the next chronicle i will be hooking up the PD to a transimpedance amplifier...
1 comment:
i commend ur efforts but what about creating the PCB for this vlc transmission from scratch without involving an already made arduino
if u have details on this kindly send me ur design details including the list of all the components that should be on board and its implementation on the desktop and laptop and not just the oscilloscope
kindly send details to mitchoes@yahoo.com
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