In the example sketches provided, the sensor produces a variable response, which seems to normalize after a few seconds on-target.
For example, if I target a cold surface, the sensor will drop in value, then slowly drift up to ~1200, if I retarget to a stove burner, it will max out at 2000, then slowly drift down to ~1200.
Is there a configuration option to produce a raw response which is stable and indicative of the temperature of the target surface? Or am I not grasping the fundamental nature of this sensor?
Thanks,
Matt
Your observations are completely correct! The on-board sensor is a Pyroelectric Infrared Sensor (PL-N823-01) from Kemet Electronics. The sensor has crystals inside that are sensitive to infrared emissions, like from a human hand. Those crystals interact with an internal transistor which varies the output voltage based upon the ambient infrared emissions. With that said, the downside being once the crystals are introduced to an emission they will begin to saturate. So it’s about seeing spikes that indicate “events”, like a hand waving over the sensor. That boils down to, at a high level, this sensor isn’t capable of measuring object temperature (or distance for that fact). Loosely, you could determine approximations based upon the amplitude of the spiked signal, but these will have significant degrees of error based upon your operating environment, speed of said event, or other factors.
The note you’ve made about the behavior of a cold surface is also interesting. That behavior is also to be expected. You can even observe this behavior if you hold your hand over the sensor for approximately 10 sec. and observe the dip in values when you remove your hand. That behavior just indicates a ‘negative’ change in the environmental emissions. This could be used to trigger “removal events” or whatever more snazzy term you come up with!
Below are links to datasheets and education material provided by Kemet Electronics specific to this sensor. We can’t wait to see what projects you build with it!
https://content.kemet.com/datasheets/KEM_SE0206_PL.pdf
https://www.hackster.io/videos/504?utm_ … b4c1ce202a