The throttle says 24-72V. What voltage are you supplying it? If you are connecting it as the pot was, that is likely 5V.

 

The description is wrong, what they mean is that the throttle can be used on an e-bike that has a battery typically between 24-72V, which has absolutely nothing to do with the actual applied working voltage of the throttle, about 4.8 to 5.2V, which corresponds to what most Hall devices require to operate.

 

The description is wrong, what they mean is that the throttle can be used on an e-bike that has a battery typically between 24-72V, which has absolutely nothing to do with the actual applied working voltage of the throttle, about 4.8 to 5.2V, which corresponds to what most Hall devices require to operate.

Well, the evidence that is wrong is that it is not working. Dies the manufacturer / seller state this just your assumption.

Previously you said this:

they need a way to generate the 5.2V supply off the 90V (max) input, so they must have a linear regulator in there

If your 5.2 V is being fed into a 5V regulator, it is not likely to work.

 

they need a way to generate the 5.2V supply off the 90V (max) input, so they must have a linear regulator in there, as there aren't any inductors on that board for a switching power supply.

Perhaps D1 (marked as a zener) is a 5V zener. If the pot is 10k it would only draw 1/2 mA so a zener could easily provide that without the need for a more complex regulator. It is unlikely the IC control input needs much current.

Edit:
The terminations of D1 look burnt, and their soldered joints are suspect.

 

Perhaps D1 (marked as a zener) is a 5V zener. If the pot is 10k it would only draw 1/2 mA so a zener could easily provide that without the need for a more complex regulator. It is unlikely the IC control input needs much current.

Edit:
The terminations of D1 look burnt, and their soldered joints are suspect.

Where is the picture and schematic you are referring to?

 

Perhaps D1 (marked as a zener) is a 5V zener. If the pot is 10k it would only draw 1/2 mA so a zener could easily provide that without the need for a more complex regulator. It is unlikely the IC control input needs much current.

Edit:
The terminations of D1 look burnt, and their soldered joints are suspect.

Yes indeed you're right, pot is 10K so no need for a regulator. If the chip takes <2mA, we're still below ¼W dissipation.
D1 looks fine from up close. And the control chip has no markings whatsoever.

@BobTPH The pic is in post #1

 

I'm trying to replace the potentiometer of a PWM speed control, by a thumb throttle that is based on a Hall sensor, as practically all thumb throttles do. It's easier to actuate than turning a pot.

But the "thumb throttle" (from what I just read) is not electrically equivalent to a potentiometer, so you can't just swap on for the other.

 

Both take a supply of around 5V, and both output a variable voltage to the input of a chip.

 

D1 looks fine from up close

D1 itself looks fine, but where its leads enter the board there's what looks like sooty connections with irregular solder round the edges.

 

I just cleaned it with alcohol, it was flux residue. The solder is a little frosty there, but still a good joint.

 

1) How much current does the Hall device draw when disconnected from the controller?
2) What supply voltage are you using for test purposes?

 

I'm supplying the board with 60V, as my project will run on 52V lithium batteries. The board can take up to 90V.
Thanks to you, I found the problem! While testing the running current of the Hall device from the speed controller, I noticed that I didn't have the full excursion of output voltage that I had previously measured when i tested it from a separate supply of 5.2V. In the circuit, it pulls down the 5V line to 3.4V, drawing 3.4mA while doing this, and that is the reason that the board doesn't work.
All along this thread, I was certain that I had checked the Hall on the board's supply, after having tested it on a separate supply, but obviously I didn't. Actually, the Hall still works on 3.4V, with limited output range, but the chip doesn't.
I'm sorry for having made you all loose time on this thread, this is a humbling experience. My 72years old mind is certainly not as awake as I thought it was. Thanks for all your contributions!

 

So, the Hall device behaves more like a 1k pot than a 10k one and the 5V supply can't provide much current. I guess you'll be building your own, more robust, 5V regulator? Or get one like this?

 

Previously, I have observed that checking voltages after making changes in a system will reveal unintended changes in some unexpected locations.
THAT is the reason for looking at the whole circuit instead of just guessing as to what it is and how it works.

 

As per my post in #2, that board is quite small that reverse-engineering it should be quite trivial!
That would solve any mystery as to what it accepts! ??

 

Thanks for the link Alec_t, I'm going to order one.
@MaxHeadRoom, yes that would have been the thing to do. I have too many projects and not enough time!

 

If the Hall sensor in the throttle is similar to one of these, its supply current from a 5V supply could be up to 9mA. Not surprising that the speed controller won't accept it.

 

The reality is that there is more to creating a feedback control system than just replacing the setpoint portion with a feedback signal. THAT ONLY WORKS in block diagram systems. In the realworld it is not quite that simple.