I've developed a new concept called "Ambient Light Ignoring Infrared Active Distance Sensor". It consists of a transmitter with an infrared LED which uses a traditional LM555 timer to oscillate a frequency of 5kHz and a modified receiver which consists of a common emitter setup, NPN phototransistor and a filter. What I've done with the receiver is to replace the RLC circuit with an Inverting Band Pass Filter circuit and removed a significant part of what once was a receiver for a motion detector. Originally the circuit was designed to only allow negative voltages to pass through the first operational amplifier in the receiver circuit, store the voltage in the C4 capacitor (as far as I'm concerned) and output a signal that sounds an alarm, when the voltage overcomes the threshold voltage (as far as I'm concerned). The new design is designed to allow all the voltages to pass through, in order to constantly monitor the voltage which would depend on the distance the infrared light travels from the transmitter. (The 1N4148 diode's purpose is to make sure that the current only goes one direction, to i.e. prevent damage in the circuit). So my question to you is following: 1) Will the voltage pass through the receiver circuit to output despite that I removed; a) The operation amplifier of 50K which sets the threshold b) The operational amplifier IC2B c) The capacitor C2 which stores the negative voltage d) The 22K resistor 2) Would the following apply also for my circuit despite the changes: The voltage output would vary with the distance between the infrared LED/NPN phototransistor. 3) Do you agree that the difference between the motion detector and my distance sensor is that, I'm allowing all voltages to pass through instead of outputting a signal only if the voltage is high enough? I've published all of the required information needed to answer my question on the following website: http://cognitivenetwork.yolasite.com/ [Broken] Note: The pictures are on the right, and the drawing bellow is of the original motion detector. Sincerely, BE student in Mechatronical Engineering.