Why am I killing hall effect throttles?

Good evening all,
I am trying to get my electric motorcycle build from 95% to rideable before the weather prohibits that. I had hoped to have only a week left to go but I apparently set myself back tonight.

I ordered a replacement throttle since the one that came with the (used) bike appeared to die during some testing. It would only put out 60-80 mV, with no relationship to position. I was puzzled by the sudden death, but I ordered another one to replace. I made a new 5v supply for it from a USB car charger, from which I get nice, clean 5v power. I am feeding the signal into an Alltrax 7234. After wiring things up tonight, I got nothing out of it. No signal that the 7234 was getting signal, although I could see the voltage sweet with a multimeter if I put the meter on the throttle directly. When I reconnected to measure while it was connected to the controller, that's when I got the millivolts signal of death- the second throttle had died without giving me a single mile! What did I do wrong?

are you certain that the hall effect sensor is dead?

if it has more current delivered to the signal lead than the transistor is specced for then it would cause it to die. if there is high voltage on the signal line from the controller it would do that. imo.

I'm using a 5v USB charger that puts out a nice, steady 4.95-5.05v. Do I need a series resistor or something? The controller is an Alltrax AXE 7234.

Weird, I test Hall throttles all the time in order to decipher wiring color codes and haven't cooked one yet. I normally use 5-7Vdc battery supply reversing suspected gnd-tho leads to find the one that delivers a few mV up to slightly under supply voltage when operated.

Unlike switching Hall sensors found in motors, variable throttle Hall sensors don't seem to require any pull-up/down resistor to deliver measurable variable voltage to a volt meter.

dont your controller have a 5v supply of its own to power the throttle ? or has it only a 2 wire input for the throttle ? . Can your controller accept a hall type throttle?.

with your 5v supply do you get a nice voltage signal out of the throttle without it connected to the controller even though you suspect that the throttle are blown ?
i.e 0 to 5v output as you twist the throttle

what is the input resistance of your controller , signal to gnd ? ( without the throttle connected )

edit: the only things that commonly kill hall sensors in throttles are over voltage, as most are protected against reverse polarity and shorts on the output.

The controller takes a 2-wire input, does not supply 5v, and is programmable to use any of about ten different input possibilities.

When I tested the voltage sweep of the hall when disconnected from the controller, I got about 0.88v-4.55v. I don't know the input resistance of the controller, but I am leery to check as I know sensitive instruments can sometimes be damaged by the current passed by the multimeter to get a resistance reading.

nedfunnell said:

The controller takes a 2-wire input, does not supply 5v, and is programmable to use any of about ten different input possibilities.

When I tested the voltage sweep of the hall when disconnected from the controller, I got about 0.88v-4.55v. I don't know the input resistance of the controller, but I am leery to check as I know sensitive instruments can sometimes be damaged by the current passed by the multimeter to get a resistance reading.

Click to expand...

you should not have the controller powered when checking the input resistance so no damage should be caused to your meter or the controller... when the controller is powered on is there any voltage on the 2 input wires to the controller without the throttle connected ?

yep, that is what i wondered since he implies he has shorted out two hall sensors in a row. since there is no current limiting it would just blow the hall sensor transistors. he may even have a floating ground with high voltage separating the throttle from the controller.