Brake signal V out of whack?

[alban]

Wuxing cheapo cable brakes with non-sine KU63 motor controller.
Trying to get brake cutoff to work. Motor works but won't cut off when either brake lever pulled. When brake off signal is 4.5V and when pulled drops to 2V, not 0V. Both sides.
Presumably the KU63 needs signal to drop to 0V?
Can't work out how to free signal cable from brake handle to inspect without destroying it! I can't seem to move the sensor further away from the handle - is that adjustable somehow?
The cutoff prev worked with a no-name ebay controller but was occas erratic.
The 5V rail measures 4.5V in several places so seems to be the max poss.
Pretty sure I've got the right wire as the signal does change with braking.
Any ideas?
Thanks

 

[vfr400]

The signal wire is held at 5v by a pull-up resistor. When you operate the brake switch, it's connected directly to ground, so cannot show anything other than 0v. The signal wire is monitored directly by the cpu to see if it's a high or low signal.

There must be something wrong with your ground (black) wire in the brake cable - maybe not soldered properly. Try bridging the signal wire directly to the battery negative to see if it cuts out, then you can figure out what needs to be done to repair the black wire.

 

[alban]

Thanks. OK so connecting to the batt neg gave 2V too! Tried a different batt, still 2V. Ooh er maybe my meter is on the blink?! But it's measuring the 4.5V ok?

 

[vfr400]

Thanks. OK so connecting to the batt neg gave 2V too! Tried a different batt, still 2V. Ooh er maybe my meter is on the blink?! But it's measuring the 4.5V ok?

When you bridged it, did it cut the motor?

 

[alban]

When you bridged it, did it cut the motor?

Yes when I bridged the signal to batt neg it stopped the motor

 

[vfr400]

Yes when I bridged the signal to batt neg it stopped the motor

Then it should work when you operate the brake switch unless the black wire isn't connected to ground.

 

[alban]

Then it should work when you operate the brake switch unless the black wire isn't connected to ground.

OK, thanks again, so I'll check continuity but what I don't get is why the other controller works then?

 

[vfr400]

OK, thanks again, so I'll check continuity but what I don't get is why the other controller works then?

You never mentioned another controller before. Tell us about it.

There is nothing simpler than brake switches. One side is ground and the other side is floating at 5v. When the switch is on, the 5v gets taken down to 0v. The switch is either on or off. You can test that with any meter.

The switches are not adjustable. The switch is sprung to the on position when nothing touches it. When the lever is in the home position, it pushes the switch into the off position. If you have too much slack on the cable and weak springs so that the lever didn't go all the way home, it's possible that the switch could stay on all the time.

You remove the switch from the inside of the lever holder after removing the lever from its pivot. The little threaded collar on the outside holds them in. If that were too loose, the switch could move forward a bit, which would mean that you would have to pull the lever further to make the switch come on.

 

[alban]

Yes I gave the other controller a brief mention in the first post. It's an ebay 36V 350W and which isn't road legal due to me tinning the shunt and doesn't have a speed limiter. When I plumb it in the brake cutoff works. So that indicates that there's continuity in the ground wire in the bike harness? The Vs are the same 4.5V dropping to 2V when brakes pulled. It's why I found it confusing.
The brake lever looked like it was riveted so didn't remove. I tightened the sensor collar to max. Yes wondered if the switch was ma!functioning but it's the same Vs R and L and as you say should be just on or off.

 

[alban]

OK so solved it. Whilst the Tonaro Bighit wiring diag specifies all Grnd wires are black and the sole orange wire is 'weak electric signal' the orange wire was in fact the brake Grnd wire! Checked continuity from brake signal connector hidden in frame. Now works fine with orange connected to controller Grnd.
However why does the brake cutoff work on my previous controller?! Maybe it registered the V signal change without the Grnd taking it to 0V?
Many thanks to vfr400 for his patient coaching.
Moral? Don't assume the wiring diag is correct and check everything even if it doesn't seem to make sense.