lifetimeproximity-sensorultrasound
I see ultrasonic transducers used in many Arduino and similar applications for proximity sensing.
I wonder what is the lifespan of such devices (Chinese cheap models, not Chinese more expensive ones) when used about once a second.
I don't consider the use outside specifications, only regular use as from the datasheet.
As plus, additional data about more rugged transducers like the ones used in cars for parking would be appreciated.
From your explanation and other question, it seems you are connecting your IR LED directly to the ADC input. I don't think this will work too well at a distance, the ADC input will probably have quite a low impedance that will attenuate your signal. Photodiodes have a very large impedance so you need a transimpedance amplifier to convert the current to voltage.
I would use something that is designed for sensing rather than emitting, like a photodiode or your IR phototransistor (if it didin't work then you are probably not using it correctly), and feed this into an opamp, then into the ADC.
In the app note you link to, there are plenty of example circuits, all of which involve a transistor or opamp to amplify/buffer the signal. Try one of these and see how it performs.
Depending on what the shape of the treadmill is (could you provide a picture?) you could use the LEDs by making diagonal lines between the side bars and the floor of the treadmill.
Something like this:
where red circles are IR LEDs and green circles are receivers or vice versa, with some logic work should give you the control over the position of the dog.
You will have some interference between the LEDs but you can use modulation or some form of synchronization to deal with it.
Best Answer
What is the lifespan of ultrasonic transducers like the ones used in hobby projects?
Piezoceramic transducers (the more expensive ones) have a long life. They also have less sensitivity. They are usually stacked with acoustic damping material at the rear of the transducer and epoxy with hollow micro spheres in the front of the transducer element as an impedance matching mechanism.
Diaphragm ultrasonic transducers (less expensive ones) usually have the flexure element (diaphragm) exposed to the air. They have a higher sensitivity, but are more vulnerable to environmental conditions such as dust, moisture, and aging of the diaphragm. As a result, these have a shorter life span than the piezo types.