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From: "Pierre de Vos"
Subject: Photodiode Sensor
Date: Tue, 17 Sep 2002 01:01:51 +0200
X-Newsreader: Microsoft Outlook Express 5.00.2919.6700
I need to build a light pulse sensor using a photodiode. The sensor needs
to be immune to ambient light, which probably means that it has to be AC
coupled. Also the pulses may be modulated with a frequency of say 1kHz to
10kHz. I can probably band-pass the output of a transimpedance amplifier
with enough AC gain to give a usefull signal when the signal is modulated.
The problem is though that I also need to be able to detect un-modulated
pulses (with the same sensor) of up to say 100Hz. After doing some initial
filter design, I'm worried about the step response of the filter, in that
for un-modulated pulses it may give triggers for both rising and falling
edges (the overshoot on the falling edge could also cause a trigger).
Does anybody have some ideas?
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