Using a potentiometer twist throttle on a ebike with a hall sensor

Thread Starter

JamieRX

Joined Nov 8, 2020
9
Hi to all members ,I’m hoping I can find out the answers to my questions on here . Basically I’ve recently purchased a Super73 RX ebike . It’s powered by a rear hub motor in conjunction with pedal as l assist . Being a EU model it doesn’t come with a throttle as std however they are bring one out later this month. This will be for off-road purposes only . The throttle is a thumb type unit and is designed to simply plug into the female bafang type terminal that’s on the bike ready . I would like to use a twist throttle and the one I want to purchase is a Magura 317 .
The description is as follows


Complete throttle grip model 317 Magura

Motokay item number: 3237571

DESCRIPTION OF THE ITEM
This article belongs to the following categories:
Chassis »Vehicle equipment» Magura »Throttle twist grip» Electric throttle grip
Chassis »Steering» Handlebar fittings »Throttle handles» Electric throttle

Glass-fiber reinforced plastic housing for 22 mm pipe diameter. Total length approx. 150 mm, maximum load capacity 1 watt, resistance value and control range of the potentiometer 5 kOhm, control range 0-5 kOhm, cable length 1800 mm. Connection with 3-core cable with an outside diameter of 6 mm.
Rotation angle: 75 degrees

My concern is that my bike from what I’ve been told has a hall sensor so I’m not sure if this throttle will be a simple plug and play affair once I’ve soldered the correct male yellow bafang connector on .
I had read on a postwhen someone had used this throttle on their home brew ebike that they had to solder resistors in to two of the 3 throttle wires to achieve a smooth linear throttle curve ?
I hope some one can help ,and if you need more info please ask . Incidentally this Magura throttle was used on a one off limited edition build of my bike . I’ve added some info on the throttle in question
thanks
Ja
 

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Thread Starter

JamieRX

Joined Nov 8, 2020
9

mikewax

Joined Apr 11, 2016
155
well according to this, it depends on what type of hall effect sensor you're trying to substitute for. If it is a 3-wire unit then it should be simple. Those throttle sensors produce a ranging voltage level just like a pot does.
So you tap the lines on the stock throttle and measure the voltages it produces at different throttle angles.
Once you know the voltage range you need to produce, just make a circuit that will connect to the pot throttle and add extra resistors to scale it's output voltage to the input voltage that the bike is expecting to see.
 

Thread Starter

JamieRX

Joined Nov 8, 2020
9
well according to this, it depends on what type of hall effect sensor you're trying to substitute for. If it is a 3-wire unit then it should be simple. Those throttle sensors produce a ranging voltage level just like a pot does.
So you tap the lines on the stock throttle and measure the voltages it produces at different throttle angles.
Once you know the voltage range you need to produce, just make a circuit that will connect to the pot throttle and add extra resistors to scale it's output voltage to the input voltage that the bike is expecting to see.
Hi thanks for the reply ,it’s a 3 wire plug that’s hard wired on the bike ready to accept a throttle (generally bafang thumb style ) so I’m not sure if that’s what you mean regarding the three wires . I wish I had your knowledge but I’m really just a plug n play type person on electronics.
 

mikewax

Joined Apr 11, 2016
155
Hi thanks for the reply ,it’s a 3 wire plug that’s hard wired on the bike ready to accept a throttle
Well then it should be quite elementary in terms of the circuitry, probably just a couple of extra resistors. But the wiring involved could be rather tedious.
you have to tap the 3 wires somehow and use a voltmeter to measure from each wire to ground. Measure each wire at the bottom of the throttle travel and at the top. Only one of the wires will show different readings at the two different positions.
those two readings are what you need.
then you measure the resistance of the pot.
Then you'll have all the necessary info to create an extremely simple circuit to translate the pot output voltage into the necessary control input.
It will require some soldering and splicing of wires, probably next to or inside the housing of the bike's control module.
If you can do that then we can tell you all the details you need.
 

Phil-S

Joined Dec 4, 2015
205
You need to get up to speed (pun) on the different types of Hall sensors.
Some operate as digital switches, some operate as analogue magnetic field sensors. Some respond differently to whichever magnet pole is presented.
Most have three wires, supply, ground and a some sort of data output.
I wonder why they choose a Hall sensor when throttle applications might use some sort of potentiometer?
You say it doesn't come with a throttle which sounds a bit strange, but there might be reasons for that, with the motor only responding to pedal effort.
You could put something together like a simple potentiometer, but I would exercise a lot of caution as there might be more to it than appears at first sight.
Anyhow, hacking what you have is a bit ambitious and if you got it wrong, the results could be interesting
 

Thread Starter

JamieRX

Joined Nov 8, 2020
9
You need to get up to speed (pun) on the different types of Hall sensors.
Some operate as digital switches, some operate as analogue magnetic field sensors. Some respond differently to whichever magnet pole is presented.
Most have three wires, supply, ground and a some sort of data output.
I wonder why they choose a Hall sensor when throttle applications might use some sort of potentiometer?
You say it doesn't come with a throttle which sounds a bit strange, but there might be reasons for that, with the motor only responding to pedal effort.
You could put something together like a simple potentiometer, but I would exercise a lot of caution as there might be more to it than appears at first sight.
Anyhow, hacking what you have is a bit ambitious and if you got it wrong, the results could be interesting
Hi thanks for the reply . Right to answer some of your questions back to me
The bike whilst being a US brand “Super73 “ the model I have is from Super73 Europe and therefore due to different laws to the US the EU bikes come with 10 speed and a torque sensor bottom bracket but no thumb throttle (although the Higo male throttle outlet is there ready ) where as the US bikes have single speed ,cadence sensor and thumb throttle. I’m now looking a getting the domino 0-5k twist throttle which is a potentiometer type but I’m told seeings I only have 3 wire connector on the bike I need to ignore the two green throttle wires and use the other three but add resistors to two of the wires to eliminate and dead spots .
hope that makes sense . I think I need to measure the output from the signal wire on my bike to know what resistors I need ?
 

Phil-S

Joined Dec 4, 2015
205
The US and Europe bikes are quite different in specification.
They are also quite expensive.
I would be very cautious tinkering around with the electronics.
You could see what voltages are present at the Higo? outlet/connector?.
You could be looking at a ground, supply, and possibly a data/voltage line, but the readings might not tell you much of any use.
Personally, I would try and get a lot more information before going anywhere near it with a different speed control method, it could be an expensive experiment.
Is the "signal" wire the same as the throttle outlet cable you refer to?
There are some e-bike forums that might throw up some better information.
 

Thread Starter

JamieRX

Joined Nov 8, 2020
9
They are not experienced either I just know they used the same throttle but I will see how the resistors play out when they fit them
 
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