Throttle not responding

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Cr1sp   10 µW

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Throttle not responding

Post by Cr1sp » Jan 24 2023 12:50pm

I have a throttle that does not respond to any input, here's what I have done so far;

- I used a generic 'general ebike tester' that has a built in throttle tester to test the throttle and it was working fine, to be sure, I hooked 5v to the throttle and with a multimeter, I measured the outout which was fluctuating between 0.8v and 4.8v as I was twisting it which looks normal.
- I then measured the voltage at the controller throttle plug which was outputting 5v. To make sure, I used a piece of wire to connect the 5v with the input and the motor was spinning full power so I believe there's nothing wrong controller side.

I verified that the throttle works and that the motor spins without throttle plugged in, I and then found an old throttle laying about, I did test it with ebike tester and with a multimeter, passed both tests, hooked it up and still nothing. I then hooked up my multimeter between the controller and throttle on the 5v supply side, what I noticed is, on the output with the throttle disconnected I'm getting 5v from the controller but as soon I plug in the throttle, the output drops to 1.2v, as soon I disconnect it, it goes back to 5v. I then connected my multimeter on the signal/input side, with throttle disconnected it's at about 20mV which looks normal but when I connect the throttle, it jumps to 400mV-550mV and stays there and it does not change no matter how far I twist the throttle.

I have no idea what else I can try. I did order a brand new throttle but it will take few days to arrive. Only thing that comes to my mind is perhaps there might be a short somewhere hence throttle does not work and why the voltage drops but it works fine when I connect the 5v straight to the input controller side? I inspected the wires and they all look ok. Any input is appreciated.
Last edited by Cr1sp on Jan 24 2023 2:05pm, edited 1 time in total.

Voltron   100 MW

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Re: Throttle not responding

Post by Voltron » Jan 24 2023 1:05pm

That sounds like something inside the controller, since the throttles are passing. Maybe 5v regulator failing? Maybe hidden short/insulation break in the throttle wires harness somewhere?

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Re: Throttle not responding

Post by Cr1sp » Jan 24 2023 1:21pm

Voltron wrote:
Jan 24 2023 1:05pm
That sounds like something inside the controller, since the throttles are passing. Maybe 5v regulator failing? Maybe hidden short/insulation break in the throttle wires harness somewhere?
Regulators failing did cross my mind but eliminated it because if that was the case, wouldn't the voltage drop when I bypasses the throttle and put a wire between 5v and the signal/input? When I did that it was exactly 5.00V, didn't even drop a single mV. Unless the failing 5v regulators can't handle the few mA that the throttle is consuming, I could measure how much but surely it can't be much. I guess I could put 5v to the throttle myself and only hook up the signal wire to the controller and see if the throttle works then?

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Re: Throttle not responding

Post by Voltron » Jan 24 2023 1:25pm

Did this happen on a running system, or is it a new build?

Cr1sp   10 µW

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Re: Throttle not responding

Post by Cr1sp » Jan 24 2023 1:29pm

Voltron wrote:
Jan 24 2023 1:25pm
Did this happen on a running system, or is it a new build?
Running system, I probably should've mentioned this in my post but on the day when the throttle stopped working, I was experiencing delays when I was letting go off the throttle, sometimes it would take a solid second for the power to cut out after letting go off the throttle, sometimes it would slowly reduce power after letting go until it stopped instead of instantaneously cutting it out.

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Re: Throttle not responding

Post by Voltron » Jan 24 2023 1:30pm

That almost sounds like an increasingly worse short in the plug itself maybe?
If plugging in different throttles makes the 5v voltage drop the same way, it's got to be in the controller direction somehow?

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Re: Throttle not responding

Post by Voltron » Jan 24 2023 1:34pm

Does the voltage on the signal wire going to the controller change as a throttle gets plugged in?

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Re: Throttle not responding

Post by Cr1sp » Jan 24 2023 2:07pm

Voltron wrote:
Jan 24 2023 1:34pm
Does the voltage on the signal wire going to the controller change as a throttle gets plugged in?
Yes, I mentioned this in my post, it's at 20mV with nothing plugged in and it jumps to 400mV-550mV when I connect the throttle.

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Re: Throttle not responding

Post by Voltron » Jan 24 2023 2:46pm

With both throttles?

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Re: Throttle not responding

Post by E-HP » Jan 24 2023 2:56pm

Cr1sp wrote:
Jan 24 2023 2:07pm
Voltron wrote:
Jan 24 2023 1:34pm
Does the voltage on the signal wire going to the controller change as a throttle gets plugged in?
Yes, I mentioned this in my post, it's at 20mV with nothing plugged in and it jumps to 400mV-550mV when I connect the throttle.
The signal line should typically be between 0.8V-0.9V when plugged in. 0.55V seems a little low.

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Re: Throttle not responding

Post by fechter » Jan 24 2023 4:17pm

That's pretty strange.

It sounds like the throttle is pulling down the 5v supply. The 5v supply in the controller has a limit to how much current it can source. The combined load of the stuff connected to it seems to be too much for it. Either the 5v supply is too weak or the throttle (or some other part) is drawing too much current.

Just for fun you might try disconnecting the motor halls and measure the 5v on the throttle and see if there is any difference.
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Re: Throttle not responding

Post by amberwolf » Jan 24 2023 10:04pm

It's possible. A 78L05 5v regulator (one of the typical supplies controllers use) can output only around 100mA. If the total load is higher than that, it'll have trouble maintaining 5v.

The Honeywell SS49E linear hall sensor takes around 10mA from the 5v supply.

A typical SS41 bipolar hall sensor in a motor (of which there are at least three for any sensored motor) can take 10mA (or more) just to power it, and then when it turns on it also sinks current thru the pullup resistor. If it's a 5kohm, assuming around 4v across the pullup, that's just under 1mA more, for some portion of the motor rotation, for each of the three sensors. So 30mA+ all the time, and call it up to 2mA more at certain times.

If the motor has two sets of halls and they are both powered at the same time (even if not both connected to the controller's pullups), that could be 60mA+ just for those.

If there's a separate speed sensor, or hall-type ebrake sensors, they could each take another 10mA.

The MCUs commonly found on these I couldn't find a max current for (minimums are in the uA range though). Let's call it <1mA. If they run off 3.3v instead of 5v then the regulator for 3.3v will take current, probably significantly more than the MCU itself does.

Any controller-powered LEDs, Bluetooth, etc., also take current, as will any other 5v-powered devices.

So...adding that up, there's a minimum of around 32mA+ (motor halls) plus 10mA (throttle) plus 1mA+ (MCU).

That's only half the supply, so that should be ok. But...those are all parts I know spec sheets for, and don't include the actual parts often inside these things, which are not usually the "brand name" parts those specs are for, but rather clones (or clones of clones), which may take less (or more) current to run them, though probably not double.


If something is wrong with the throttle hall, though, it could draw a lot more current than designed, and drag the 5v supply down. Especially if there are other devices not accounted for above powered from the same supply.
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Re: Throttle not responding

Post by amberwolf » Jan 24 2023 10:06pm

Cr1sp wrote:
Jan 24 2023 1:29pm

I was experiencing delays when I was letting go off the throttle, sometimes it would take a solid second for the power to cut out after letting go off the throttle, sometimes it would slowly reduce power after letting go until it stopped instead of instantaneously cutting it out.
That sounds a bit like the "bad throttle ground" problem that can also cause unintended motor operation, or runaway bikes. It can happen from a poor connection anywhere between the throttle hall sensor ground pin and the controller PCB pad for throttle ground.
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Re: Throttle not responding

Post by Cr1sp » Jan 25 2023 1:56pm

Voltron wrote:
Jan 24 2023 2:46pm
With both throttles?
Indeed, with both.
E-HP wrote:
Jan 24 2023 2:56pm
Cr1sp wrote:
Jan 24 2023 2:07pm
Voltron wrote:
Jan 24 2023 1:34pm
Does the voltage on the signal wire going to the controller change as a throttle gets plugged in?
Yes, I mentioned this in my post, it's at 20mV with nothing plugged in and it jumps to 400mV-550mV when I connect the throttle.
The signal line should typically be between 0.8V-0.9V when plugged in. 0.55V seems a little low.
Exactly, when I tested my throttles with external power source, minimal reading I was getting was 0.8v so that's what the controller should be getting.
fechter wrote:
Jan 24 2023 4:17pm
That's pretty strange.

It sounds like the throttle is pulling down the 5v supply. The 5v supply in the controller has a limit to how much current it can source. The combined load of the stuff connected to it seems to be too much for it. Either the 5v supply is too weak or the throttle (or some other part) is drawing too much current.

Just for fun you might try disconnecting the motor halls and measure the 5v on the throttle and see if there is any difference.
I tried it, with no throttle plugged in or hall sensors, I get perfect 5.00v, when I plug in the throttle, voltage on the throttle supply drops to 1.2v but the hall supply stays the same.
amberwolf wrote:
Jan 24 2023 10:06pm
Cr1sp wrote:
Jan 24 2023 1:29pm

I was experiencing delays when I was letting go off the throttle, sometimes it would take a solid second for the power to cut out after letting go off the throttle, sometimes it would slowly reduce power after letting go until it stopped instead of instantaneously cutting it out.
That sounds a bit like the "bad throttle ground" problem that can also cause unintended motor operation, or runaway bikes. It can happen from a poor connection anywhere between the throttle hall sensor ground pin and the controller PCB pad for throttle ground.
That did cross my mind but if it was bad ground, the controller would be stuck full throttle as it would be getting 5v or whatever the supply throttle voltage is but instead its opposite, it doesn't even get minimum voltage which should be 0.8v. Maybe I'm not looking properly but can't find any threads about people having the same issue as me.

Thank you all for suggestions and input. After probably spending solid 4 hours on this and running out of things to try and troubleshoot, I arrived at the conclusions that it's probably either;
1. An internal short inside the controller or on the PCB
2. A faulty 5v regulator on the throttle output.

I did get the throttle working in a bit of a janky way but it works for now and probably will stay like that until I find what's wrong. I initially looked in my parts bin for a 5v regulator to power the throttle as I have a 12v DC-DC on my bike already but only found a 5v buck converter which I thought will work so I tried it but turned it had isolated ground so the throttle was just stuck at 5v, had to look for something that passed ground. Didn't find anything so I used the PAS connector on my controller which I don't use to power the throttle with 5v and only ran the signal wire to the throttle plug and the throttle works just fine. I even used the ground from the throttle plug so I was only using the 5v supply from the PAS connector so whatever is wrong with the throttle plug, it has to do with the 5v supply wire or regulator. Not the ideal solution but it's better than replacing the controller or having the bike sit due to no throttle.

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Re: Throttle not responding

Post by Voltron » Jan 25 2023 2:17pm

That puts me back to thinking it could be a physical short, either in the plug, or hidden where the wires enter thru the controller case.

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Re: Throttle not responding

Post by fechter » Jan 25 2023 3:40pm

If the hall supply stays at 5v but the throttle drops, there must be some resistance between the 5v supply and the throttle 5v.

With no power, you could try measuring resistance between the hall sensor 5v line and the throttle 5v line. Normally these are directly connected.

You might have a bad solder joint or fractured wire on the controller board that's feeding the throttle 5v. Bad solder joints are not uncommon. I'd take apart the controller and look around where the throttle wires attach.
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Re: Throttle not responding

Post by amberwolf » Jan 25 2023 8:26pm

Cr1sp wrote:
Jan 25 2023 1:56pm
I tried it, with no throttle plugged in or hall sensors, I get perfect 5.00v, when I plug in the throttle, voltage on the throttle supply drops to 1.2v but the hall supply stays the same.
Some controllers have a diode on the throttle supply (or the hall supply) to protect against wiring shorts to high voltage (because some controllers have battery voltage on their throttle wiring cable as a separate wire or pair of wires to run a voltmeter or other battery-gauge).

If yours does have a diode on the throttle 5v, it could prevent the actual 5v supply from being pulled down anywhere except at the throttle itself (and any wiring up to the diode), so a throttle or wiring problem causing high loading of 5v line would only drop the 5v at the throttle supply.

A problem with the diode itself can also cause this, because it would drop voltage under even minimal load, so that no device powered from it would work correctly. This can be the diode itself failed, or a solder/connection problem at the PCB the diode is mounted to.

Since this won't affect the other 5v sources (PAS, motor hall, etc), it makes sense that it's working with the PAS 5v, especially if the problem is with a diode (or connection fault) in the throttle 5v line itself inside the controller.

If you're up for it you could open the controller and connect the throttle's 5v supply line to the pad for the PAS 5v supply, to neaten your wiring.
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