The pins of receiver are inverted?The longer is negative and the shorter is positive?
So you think that the IR receiver and emmiter are more appropriate for this project?
I tried 10k but the output is frozen, and keep showing 14.
I have a IR kit 5mm LED, is it possible to modulate the LED signal?
White light is preferable because turbidity is a visible effect, so it makes no sense at all to use IR to measure it.
That suggests it it too sensitive and the photo transistor has saturated. So reduce the value of the pull up resistor, try 1K.
Yes, but if you modulate it then you must include at the sensor end an amplifier with a frequency response that rejects DC signals and responds only to the modulation frequency. That helps with stray light, but for proper measurements your equipment must be made to measure this in the dark to have any meaning. Given you are supposed to be a University student then I would have thought that this was blindingly obvious.
You have the arrow pointing in the wrong direction in you block diagram you gave in the first post in the thread. Again not a mistake one would expect from a University student.
I guess you have already seen this project:https://www.academia.edu/8319858/Open_source_mobile_water_quality_testing_platform
It is not in the wrong direction.The yellow portion is Light, so when it hits the hole only the portion that is parallel to the hole passes
What is the name of this amplifier that you mentioned? Is it expansive?
It is called a "tuned amplifier" an amplifier with a specific frequency response that peaks at the modulation frequency. This is not the sort of amplifier you buy but one that you make.
HI,I think you are going to keep having problems if you are trying to read very small DC values.My approach would be to modulate the light source and use a optical semiconductor detector.The receiver detects the modulated light, you filter and measure its amplitude.
Surely you have resources there at the University that has a chemistry or analysis department that has one of these devices or can supply info about them.
So the yellow portion has an arrow on the end, this is pointing to the left. This says to anyone that the light is traveling from right to left.But on the right you label a box saying LDR or receiver, and on the left the box is labeled LED or IR emitter.You might not have seen the triangular yellow portion as an arrow, but I assure you the rest of the world does.
I thing you mean expensive. It is called a "tuned amplifier" an amplifier with a specific frequency response that peaks at the modulation frequency. This is not the sort of amplifier you buy but one that you make.
which swaps the amplifier (op-amp) between inverting and non-inverting, and integrate (low pass filter) the result.
If the ADC is sufficiently fast (or you use a much lower frequency that the 38 kHz I mentioned, such as 700 Hz), you can perform this in the Arduino.
My thoughts were that the kind of light would not interfere on it. Because in other words what I'm trying to measure is the amount of particles in water that are blocking the light.
This one that you mentioned (74HC4066) would be able to amplify the signal to 38 kHz or even 700 Hz?
Drive your LED (white will be fine) from a digital output via a resistor, and use a photodiode or phototransistor to measure the height when its ON.Then take another measurement when its OFF and subtract the two.
The best way to eliminate external effects is to use a square wave rather than a continuous signal. Choose a frequency that is not a harmonic of mains frequency.
The best way to eliminate external effects is to use a square wave rather than a continuous signal. Choose a frequency that is not a harmonic of mains frequency.Drive your LED (white will be fine) from a digital output via a resistor, and use a photodiode or phototransistor to measure the height when its ON.Then take another measurement when its OFF and subtract the two.I'd still recommend you exclude ambient light.My page here shows how to drive an LED.