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April 24, 2010
about 5 years ago
Yes, this hall effects sensor latches on/off depending on the polarity introduced to it. I needed it to latch on/off when a magnetic field was/was not present, which this is not set up to do by design. But I found a simple way around that…
I am using the sensor with an Arduino, so my implementation may not work for your setup. Instead of providing constant power (5v) to pin 1, I instead connect it to a digital pin that I have set as an output. Pin 2 goes to ground and pin 3 is read as a digital input. Note: As mentioned in other comments, I use a 10k pull-up resistor between power (digital out to pin 1) and output (digital in from pin 3) to get a clear on/off state.
In the loop code, I first set the hall sensor power pin to HIGH and delay for as short as 10ms, read the latched state from it (on/off), and then set the hall sensor power pin to LOW and delay another 10ms.
Cycling the power resets the state of the sensor so you can poll its output to see if the magnetic field (of the polarity that latches it ON) is still present or not. The delays are necessary to give it time to reset, otherwise it will give unexpected results.
This allowed me to make a simple open/closed presence sensor without having to do something funky with the magnet to get it to flip poles each time. I hope this helps!
about 6 years ago
So I noticed that in the datasheet they make mention of the RW(read/write) series that is supposed to work with the Temec Q5 tag (Q5555 mentioned elsewhere). According to the document, there should exist an ID-2RW, ID-12RW, and an ID-20RW reader. It seems the information surrounding where to purchase these readers and tags is a little elusive. Personally, I think it would be awesome to work with a rewritable tag, but where do you find these products? I’ve tried finding rewritable tags in general, but have had no luck. To the guys at SparkFun, any chance you will carry the RFID read/write series with a rewritable tag in the future?
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