Test speed controller while awaiting throttle

Telemachus

10 W
Joined
Jul 15, 2013
Messages
99
Location
Riverside, CA
I have a 48 volt speed controller I got secondhand, and it came with a throttle that was broken. The hall sensor in the throttle is destroyed and will need to be replaced.

While I am awaiting a replacement throttle, I wanted to test the speed controller. When i supply power, I am getting 4.5 volts on the positive and negative leads of the throttle wire.

I tried placing a simple 1k ohm resistor between the positive lead of the throttle and the sensor wire, and I got no movement on a working connected hub motor.

I also tried a 1.5 volt DC power supply, sharing the negative wires and applying the positive on the power supply to the sensor wire on the throttle.

Nothing.

Am I in correct in thinking that if I can get something between one and 4 volt to the sensor wire, that I should get some output?
 
I believe your 1.5 power supply is just on the threshold of the throttle start voltage. Stack an AA cell on top of it or use two AA cells in series if you have enough hands to hold them.

Also two 1K resistors twisted together in series. Put the outer ends on the power, and the middle to the sensor input. That will put 1/2 the supply voltage to the controller input. About 2.25 volts. Zoom zoom.

A diode from +V to the sensor input will do it too, if you got the polarity right. Flip it if it doesn't work.

.
 
My favorite is using a 3v button battery. :) Positive to sensor input wire and negative to negative.

But you have to keep in mind also that some controllers must be "on" to start with before you add the test voltage input. Other wise it will think there is a throttle stuck on and fault out. Also some will fault with throttle voltage less than expected...say at .4vdc and too much, say 4.5vdc.

My controller needs a quick on-off-on to trick it into running with the test battery. :wink:

Couple other options see here...
 
Thanks for the input.

I was able to supply 3V, and no go.

I tried to open up the controller to check that the hall sensor wires and phase wires are all connected, but removing the PCB sheared off some of the MOSFETS that appeared to be epoxied to the side wall.

So either way, this controller is toast now.

Time to hit Ebay...
 
Telemachus said:
I tried to open up the controller to check that the hall sensor wires and phase wires are all connected, but removing the PCB sheared off some of the MOSFETS that appeared to be epoxied to the side wall.

Sounds like you need to be a lot gentler with your stuff--it takes a lot of force to do that. :(

FETs are not normally epoxied in controllers; I've yet to see one like that, other than ones potted solid and thus not openable anyway. If yours is, it's different from the vast majority of ebike controllers.

Usually they are screwed thru their tabs to a heat spreader bar, which is then screwed to the side of the controller case with small screws on the outside of the case, between teh heatsink fins.
 
Definitely screwed to a heat spreader bar... which was in turn epoxied in. Only screws were the ones on the side plates.

And no I was not gentle at all. I was basically hammering out the pcb with a mallet.

This controller and the wheel that came with it both have a significant amount of rust and water damage. It was a long shot that it would work and I wasn't too upset about having to replace it. I was suprised there was any power to the throttle wires...
 
Well, starting to suspect you hammered that controller to death.

Easy test without a throttle is this. Lick fingers, grab positive and and 5v return wires with wet finger. should resist enough to prevent a full throttle but run it. touch the two to each other would give you full throttle of course.
 
I thought most of the speed controllers ran on a 1-4V range. So if you apply MORE than 4 volts (shorting the wires as you suggested) it would still run at full throttle? Or are they set to somehow ignore anything over 4?

And I am pretty sure that controller was dead before I started hammering, thus the reason I hammered...

:roll:
 
Telemachus said:
I thought most of the speed controllers ran on a 1-4V range. So if you apply MORE than 4 volts (shorting the wires as you suggested) it would still run at full throttle? Or are they set to somehow ignore anything over 4?

And I am pretty sure that controller was dead before I started hammering, thus the reason I hammered...

:roll:
Some controllers will work OK with over 4v. Some have a safety feature that cuts output if the throttle voltage goes over 4.6v or so (detected a short between 5v and signal).

Epoxy potting will get soft and rubbery if heated to 80-100C.
 
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