I did some experiment…I’m quite sure it is not a problem in the emitter detector displacement.
I’m confident too it is not a problem about IR light in the ambient.
I continue to think the major problem is in the circuit.
Here I attach a comparison between the two schematics showed in the makezine webpage:
As you can see, there is a mismatch in the two, missing a 1k resistor in the second schema.
I assume the correct diagram is the first, given that without that resistor I get absolutely nothing from the sesnor.
I guess there is still some error in the configuration.
I then attach some pic of my circuitry: I guess my arrangement (pic A), is correct ad follow the first schema.
NOTE, very important, I put the emitter detector one in front of the other (pic B, pic C): this means my fingertip
must be put between them…I’m quite confident the IR light from emitter can pass through my fingertip and reach the detector, see the next experiment:
Just for playing, I picked the signal directly from the capacitor in pic D (red circle). Yes I know…this is crazy but my knowledge in electronics is equal to 0!
Interestingly, I have a veeeery weak (and noisy) signal from Arduino. I mean values between 0 and 3… so I visualized on
Processing these values (enanching the values). This is what I got:
Even if the signal is extremly noisy, what I see in the visualiser seems my heartbeat rythm!
So, after this experiment, I’m quite convinced:
- the error is in the schematics furnished in the makezine webpage.
- The IR signal passing in my fingertip is usable (even if I need to clean it from noise and amplyfy it)
- I need some basic electronic issue to make the sensor work: a noise filter, and a signal amplyfier.
I’ll continue to perform experiment…now what I’ll try to do is to amplyfy the signal (ok, this is was the sensor supposed to do! ),
probably trying to rearrange the schematics.
If some guy can furnish me a basic example about Arduino and LM324 wiring, I’ll be very happy!