I watched a couple of YT videos and scanned the info at the Adafruit site. Apparently the device takes a picture of whatever is on the lens then stores it on board for future reference.
So, would it register say, a dime, then be able to compare it to other dimes to make a comparison decision?
Would it matter if the test coin were rotated 180º from the reference image?
Does it need body heat to trigger or is that a supervisory function?
Just wondering.
Depends on the sensor. Total-internal-reflection sensors only work on fingerprints, they rely on
contact with the face of the sensor by something with a refractive index similar to glass.
The prismatic shape strongly suggests its a TIR sensor.
Adafruit would probably answer your question definitively and much more quickly than waiting around for someone who happens to have one and also happens to have a dime.
MarkT:
The prismatic shape strongly suggests its a TIR sensor.
Wikipedia agrees. They refer to the peculiar species of reflection used in fingerprint sensors as 'frustrated' TIR. It's all very sciency - lots of angle theta stuff. Another application is automotive rain sensors.
Looks like coin recognition is right out.