Archive for November 25th, 2012
Two lots of linear Hall Effect sensors arrived from halfway around the planet, labeled AH49E and OH49E, and roughly corresponding to the original Honeywell SS49E. The Honeywell datasheet has a non-obvious pinout diagram (that one is better), so I poked one of them into a breadboard and tried it out.
Fortunately, I got it on the first try. Facing the tapered side, with the leads downward, pin 1 is on your left:
- Power – typically +5 V
- Output – 0 gauss = 2.5 V
The chip [may | may not], depending on which datasheet you use and which part you have, include an internal 65 μA load on the current source, so you [may not | may] need an external load resistor.
Without a load resistor, this one worked fine. Old-school ferrite and ceramic magnets push it about 1 V off-center, neodymium magnets saturate the output.
That Honeywell / Micro Switch handbook should dispel many misconceptions about proper use, calibration, polarity, and suchlike.
Memo to Self: verify the output voltage for both units with typical load resistors.