So a little idea that came to me the other day for making sensored BLDC hall-outputs
[Firstly these only work with 120 degree signals, if the hall sensors are 60 electrical
degrees apart neither of these circuits work. The 120 degree phasing is such that
either 1 or 2 signals are high at any one time]
The top circuit relies on having LEDs with a large forward voltage (blue/green/white)
so that with two in series at 5V they don't both turn on. It would be more sensible
to run at 3V3. However it assumes push-pull hall sensors which I fear is rare. It
shows 3 LEDs out of 6 lit up in a chase sequence.
The second is really just 3-wire Charlieplexing, but includes pull-up resistors
so it works with open-collector hall sensors, and shows just 2 neighbouring LEDs
out of 6 on at once and I've breadboarded and tested it with a real motor. With all the
LEDS identical the pull-up resistors will hold the lines high enough for reliable
detection, but you mustn't make the resistors too low a value and overload the hall
sensors, I've used 680 ohms and assumed 1.7V lost in red LEDs and this takes
about 10mA at most from each hall sensor.
So if you're designing a sensored BLDC driver (!!) then feel free to try these out. The
Charlieplexed circuit can simply be used to drive 6 LED circle from 3 pins if you
cycle out bit patterns: 001 011 010 110 100 101 001...