♪ Under my thumb… ♪ Hello. The new SM124 Smart GMR Magnetometer can be programmed for whatever magnetic threshold you want. A ridiculously simple I²C interface lets you program it from a microcontroller. But we also offer a self-contained board that lets you set the threshold with thumbwheel switches. First we’ll program it toward the high end
of the range— 12 Oersteds, or 1.2 millitesla. We’ll use a small amount of hysteresis to avoid bounce at the transition… push the button… and that’s it. The green LED indicates successful programming. The orange LED shows the sensor’s digital
threshold output. Now let’s set the threshold
to just one oersted, with half an oersted of hysteresis. And, as expected, it operates
much farther away. We can also reset the factory calibration
offset by just pressing this zeroing button with
no field. Here’s the board schematic: And here’s the programmer firmware: We read the thumbwheels here… Then write the threshold and hysteresis to
the sensor. And verify the programming by reading the threshold and hysteresis back out of the sensor. The firmware is straightforward, since parameters are a single byte, and the sensor’s unique architecture eliminates the need for any commands. The versatile SM124 magnetometer includes: a GMR sensor element; an ADC; temperature compensation; a clean, single-byte I²C interface; and a programmable digital threshold output. Key specifications are: 0 to 15 Oe field range, so it can detect magnets more than 50 mm away; it’s omnipolar, so you don’t have to worry about magnetic polarity; it’s accurate; it has a slick, single-byte I²C interface; the full industrial / automotive temperature range; and it’s ultraminiature. Call, click, or e-mail us for more information, or to buy SM124 sensors, evaluation kits, or programmers.