goatman said:
i did a test. I took a hall sensor and soldered red wire to left leg, black wire to center leg and green wire to right leg. took a 18650 that read 3.96v.
connected red wire to positive, black wire to negative
I connected dmm to battery red lead positive and black lead to green hall wire, no resistor, then I waved a magnet(north pole) and voltage went from 0v to 3.96v then waved south pole past hall and it switched to 0v. hall sensor is working.
then you may have hall sensors without the open-collector style output that is common for such hall sensors. most of the ones i've worked with are open-collector (like the honeywell ss411a), so they require a pullup on their output. these types give a better signal to the controller over a long wire run than the ones that output their own voltage, becuase there is no voltage drop for the high signal at the controller, as the high signal is *in* the controller. so the controller only has to look for a low signal, and it knows that anything below a certain point (say, 2.5v) is a low, and anything else is a high.
with ones that output their own voltage, rather than open-collector (oc) types, the signal strength at the controller is dependent on the quality of the wiring, and of the induced currents (and thus voltages) in the hall wires from the phase wires that run parallel to them in the motor cable, and all the other environmental noise.
so they don't typically use taht type in motors--they give terrible results, unreliable operation, without signal conditioning or special wiring, both of which are either expensive or complicated or both, and neither of which is going to happen in a cheap chinese ebike controller or motor.
it's much much simpler and cheaper to use open-collector-output type halls, and a pullup in the controller.
with open-collector halls, under some conditions, you mgiht get what appears to be a valid voltage when it isn't active (grounded), but if you don't have the pullup resistor (5k to 10kohm) from the signal wire to the 5v line, you can't really tell if the hall is working correctly or not.
this is becuase sometimes without that resistor, it will appear that the hall is working correclty at all, and so is going low-high-low-high, but if you put the pullup on there you find the hall isn't actually able to ground the signal correctly, so it never goes low, or that it is not releasing the ground properly and it never really goes high.
so if you want *definite* valid results with open-collector output halls, like the ss41 and ss411 (and clones of those) common in ebike motors, you have to use the pullup on the signal line.
without it, you can't tell if it's really working as it should, even if it "looks" like it is.
it's like a bms that has shut off it's output fets. there will still be a voltage there--but it is not "really" there, because if you put any load on it, it goes away.
I kept the dmm connected and hooked 12v bulb from positive battery to green wire of hall. hall was switching but light wouldn't work. then I serialed 2-18650 to 7.5v and got same result, hall would switch but bulb wouldn't turn on. if I connect bulb straight to battery it lights up.
the hall sensors cannot sink or source enough current to run an automotive bulb.
typically they can only do a few ma, to a few dozen ma.
the ss41 and ss411a only do about 20ma max.
an automotive bulb usually requires a few *amps* (about a thousand times as much as the hall sensor can handle). it might damage the hall sensor, but it can't light up the bulb.
you mgiht be able to use a low-power led, that uses no more than 20ma *max*, but almost any incandescent i know of (including little tiny old grain-of-wheat bulbs) will use up to several times that, and even if they work, they're overloading the hall's output and damaging it.
so...what it comes down to is that if you *really* want to knwo if the hall is working, either connect the signal lines to the powered-on motor controller so it's pullups will do the job, *or* use an external 5kohm to 10kohm resistor from hall signal wire under test to your 5v power source.
if you don't do that, you can't *really* know for sure that the halls are working correctly.
