Wednesday, 18 January 2017

identification - What is this component on my dog's door opening collar?


I am having some frustration with my dog's pet door opener. This is an off-the-shelf system from a company called HighTechPet, and the collar unit uses a coin-cell battery with a special carrier glued onto it in such a way that you cannot simply replace the battery alone: you have to order replacements with the carriers pre-attached (at a considerable mark-up) from the company.



Now, this would not be so egregious, except the batteries only last 2-3 months.


While I had the unit open for the second time, I thought I'd take a look at the circuit and try to see if the three-month lifespan is really the best that can be done. (Call me cynical, but I am suspecting not.)


Below are two pictures of the open unit with the component side of the PCB exposed.


MS4-C top MS4-C side


The component labelled MS4-C is presumably some kind of ultrasonic transmitter. Here is what the Web site has to say:



Our VP of Engineering, Bob Schilken, one of the most accomplished analog electronic engineers in the world, contributed the extremely creative directional ultrasonic detection circuitry that performs rings around conventional infared, magnetic and RFID circuits.



How might I go about finding more information on this component?


EDIT: Here are some oscilloscope traces sampled from the positive lead of the presumed ultrasonic transducer.



enter image description here


One thing that immediately catches my eye is that the lead is held high, and pings are produced by pulsing the line low with a signal that lasts 2-3ms every 25ms. Wouldn't having the line be normally high like this waste a lot of the coin cell battery power?


enter image description here


This trace is a zoomed-in view of a single ping. It appears to oscillate at 40kHz, which would put it well out of audible range (as you'd expect). I don't know why it's shaped like that, though… Some deliberate signal or just an artifact of the way the circuit and/or component behaves?




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