Torque sensor mounted on throttle connection

[BullitRadu]

Hi there.
Sorry if I put a dumb question in lack of to much knowledge about the diy kit I have installed but:
I would like to have a more progresive assistance on a Pas type kit . I also have a throttle that seems to be quite progresive.
I have found a bottom bracket with pas and torque senaor.
As much as I've seen it has 4 wires : negative ,pozitive ,torque signal (1-5v) and the pas signal.
It is possible to wire up this torque senzor to the throttle connection of the controler?
I am unable to measure the voltage in my throttle due to waterproof connections but I'd need I will cut the wires to se what's the singal range and the pozitive on it. (I don't have any knowledge obout controler type )

Thx!

 

[harryS]

Have you read ebikes.ca writeup on torque sensors? They are aomong the few people that actually sell kits that will read thse units and convert the output to something a throttle input will recognize.

PAS Options - Getting Started

Most ebikes these days offer some form of automated pedal control (PAS = Pedal Assist System), where the motor is powered in response to you pedaling the cranks and not just from a throttle on the handlebar. Here we summarize both the Cadence based and Torque based PAS sensors available for all...

ebikes.ca

 

[BullitRadu]

Thank you for your answer. As much as I've seen they've also have the dedicated display/controler setup for the torque sensor .
I already have a controler and display and looking to get only the torque sensor plugged into the throttle cable-ing.
I have added the data sheet of the torque sensor . As much as I can understand I need a voltage between 8-12 v to power it up and it will send a voltage between 1.5v and 3v on the signal wire depending on the torque I apply.
Also I have read that a e bike throttle will have a 5v supply and an output betwen 0.8 and 4.3 volt depending on position
I think I can fix the imput and find a higher voltage source but I think the output is not good for the controler to read for 0 to full

 

[harryS]

You can do the voltage translation with an op-amp, but you need to gate the signal with cadence. or your bike will have unintended acceleration all the time. What's the objective, satisfy a need to design something or have a reliable bike?

 

[BullitRadu]

I would like to enhance the experience and performance. Now I play a lot with the assistance level in order to find the proper speed and level thru out heavy trafic .
Also I would like to have a better ratio in pedaling over assistance without playing so much with assistance level. It's hard to assist the motor at the right speed when the trafic speed constantly changes .
Definitely I'm looking for reabilty and ease of use.

 

[PedalUma]

IMOP trying this will lead to potentially dangerous problems. Save up and buy a torque sensor motor for the Spring.

 

[BullitRadu]

I would like to do that but I don't know what. Definitely I won't go on mid drive . I definitely like the 2x2 traction and don't wanna mess to much with the alfine 8 belt drive to much.
I have found local some guys that can mod the controler if need and have some torque senzor that can fit my system . I will keep you up to date !

 

[scrambler]

I have actually done something similar recently on my Bike

Boxxbike Valkyrie : 12kw crank concentric mid drive with left hand motor drive

Boxxbike Customizations: Dropper post turned out perfect, with the full 125mm extended I have perfect leg extension when pedaling, and at the lowest I can mount and dismount easily or cruse with throttle. That said, even with the dropper post extended, the seating position is still too forward...

endless-sphere.com

A few things to check / clarify:
First check if your controller has an option for a torque sensor connection. If it does then that will be by far the easiest most effective way to do that, as you may even be able to connect both the torque output and the cadence info to the controller for the best possible Assist response.

If not

• Do you want to replace the throttle with the torque sensor, or have both of them in parallel (I did both in parallel)?
• Need to figure what is the voltage input of the throttle and what is the voltage input required for the torque sensor.
  • If these are not the same, where will you source power for the Torque sensor?
  • In order to be able to inject the torque sensor signal in the existing throttle connector, the Torque sensor will need to share the Ground connection with the throttle connector, so the torque sensor power source should have the same ground as the Throttle input.
• Need to figure out what is the actual output of your throttle. Easiest way to do that is to make a small harness to insert between the throttle connectors, so you can verify which wire is which and what is the voltage output of the throttle. Potentiometer throttle can have 0-5V, Hall throttle may have 0.8 - 4.3V
• Next is to install the Torque sensor bottom bracket, power it, and test its output range.
  • The potential issue here is if the torque sensor output starts at a higher value than the throttle. like if the throttle starts at .8V, but the torque sensor starts at 1.2V. In that case you would need to have a way to recalibrate it so it does not always activate the motor. If the torque sensor replaces the throttle and the controller has programmable access to may be able to do that using the controller programming, if not or if you connect both in parallel, then you would need to either use electronics or use a programmable component like an Arduino to be able to calibrate the Torque sensor.
• If the torque sensor output can be made to match what is needed and you want to connect it in parallel with the throttle you will probably need to merge the two signals using a dual Schottky diode like I had to, to prevent back feed issues.

Now know that if you only have a torque sensor as your throttle signal, that will be great for MTB kind of situations, with uneven terrain and instant irregular assist need, but it will not be great for cruising at regular speed.
When you cruise at regular speed, the pressure on the pedals is intermittent, and so the assist will be the same and therefore not very smooth or regular. This is why most pedal assist system use a combination of a torque sensor and a cadence sensor and use clever programming to blend them both depending on the circumstances.
That issue can be improved if you have a way to process the torque sensor signal, applying a Low pass filter to it, but that either require the controller to provide that, or the use of a programmable component like the Arduino.

EDIT: if the controller has the ability to add a low pass filter on the throttle signal, you can use that to smooth the Torque sensor signal and make it fairly acceptable for cruising.

 

[BullitRadu]

I have actually done something similar recently on my Bike

Boxxbike Valkyrie : 12kw crank concentric mid drive with left hand motor drive

Boxxbike Valkyrie : new 8kw mid drive with pedals and left hand motor drive .. customizable from 250w to 8000w up to 250Nm torque.. https://evnerds.com/ev-album/your-ebike/the-performance-e-bike/ facebook.com/boxxbike boxxbike.com

endless-sphere.com

A few things to check / clarify:
First check if your controller has an option for a torque sensor connection. If it does then that will be by far the easiest most effective way to do that, as you may even be able to connect both the torque output and the cadence info to the controller for the best possible Assist response.

If not

• Do you want to replace the throttle with the torque sensor, or have both of them in parallel (I did both in parallel)?
• Need to figure what is the voltage input of the throttle and what is the voltage input required for the torque sensor.
  • If these are not the same, where will you source power for the Torque sensor?
  • In order to be able to inject the torque sensor signal in the existing throttle connector, the Torque sensor will need to share the Ground connection with the throttle connector, so the torque sensor power source should have the same ground as the Throttle input.
• Need to figure out what is the actual output of your throttle. Easiest way to do that is to make a small harness to insert between the throttle connectors, so you can verify which wire is which and what is the voltage output of the throttle. Potentiometer throttle can have 0-5V, Hall throttle may have 0.8 - 4.3V
• Next is to install the Torque sensor bottom bracket, power it, and test its output range.
  • The potential issue here is if the torque sensor output starts at a higher value than the throttle. like if the throttle starts at .8V, but the torque sensor starts at 1.2V. In that case you would need to have a way to recalibrate it so it does not always activate the motor. If the torque sensor replaces the throttle and the controller has programmable access to may be able to do that using the controller programming, if not or if you connect both in parallel, then you would need to either use electronics or use a programmable component like an Arduino to be able to calibrate the Torque sensor.
• If the torque sensor output can be made to match what is needed and you want to connect it in parallel with the throttle you will probably need to merge the two signals using a dual Schottky diode like I had to, to prevent back feed issues.

Now know that if you only have a torque sensor as your throttle signal, that will be great for MTB kind of situations, with uneven terrain and instant irregular assist need, but it will not be great for cruising at regular speed.
When you cruise at regular speed, the pressure on the pedals is intermittent, and so the assist will be the same and therefore not very smooth or regular. This is why most pedal assist system use a combination of a torque sensor and a cadence sensor and use clever programming to blend them both depending on the circumstances.
That issue can be improved if you have a way to process the torque sensor signal, applying a Low pass filter to it, but that either require the controller to provide that, or the use of a programmable component like the Arduino.

Hello and thank you for your answer.
1.The controler dose not have a torque imput.
2.I want to get rid of the throttle (only torque sensor.
3.I have a hall sensor throttle ( measured 0.8-4.3 output.
The imput is 5v ( I need 8-12v) and was thinking of using a dc-dc converter on the light output of the battery.
5. The signal voltage is the sketch but as far as I've seen the ends of the throttle are dead ( I think the voltage for triggering the motor is higher then 0.8 and to achieve maxim rpm is less then 4.3) due to the fact there are waterproof comectors I'm unable to make a live test.i will cut down the cables and see what is the minim and maxim signal voltage that the controler needs on throtle

 

[scrambler]

Have you made a small harness so you could measure the throttle output ?
If you take the voltage from the light, you need to make sure that the ground of the light is the same as the ground for the throttle. One easy way is measure the Voltage between the light ground and light plus, then between Throttle ground and light plus, and see if you read the same voltage.

 

[BullitRadu]

Have you made a small harness so you could measure the throttle output ?
If you take the voltage from the light, you need to make sure that the ground of the light is the same as the ground for the throttle. One easy way is measure the Voltage between the light ground and light plus, then between Throttle ground and light plus, and see if you read the same voltage.

So I have measured the parameters and they sound like this .
The input voltage of the throttle is currently 4.3 volt. (Was wandering if I can use a buck dc-dc converter to increase the voltage.
The output of the throttle in wich the controler modifies the rpm of the motor is betwen 1.2 and 3v . (Under 1.2 motor dose not start and over dose not increase rpm ) The torque sensor I have found has a value betwen 1.5 and 3. This should be a problem because my motor will be always on on low power.
If I use a resistor I can lower the output under 1.5 but also get lower than 3 right? I won't be able to use maxim power from the engine. Is there a way to gate the signal so it will be under 1.2 v ?

 

[harryS]

Read up on op amps. You can amplify the T/S output to any level you want.

 

[scrambler]

You can probably use a buck converter as long as you get enough power out of the throttle supply.
If the throttle is 1.2-3v and the torque sensor is 1.5 - 3V I would say it is worth a try as is, and if it really is a problem, then look into a small electronic circuit that will allow you to adjust input and output.
Also some torque sensor may have some Calibration capabilities integrated, so you may want to look into that in case some BB torque sensor do have that ability.

 

[BullitRadu]

I recently found this https://a.aliexpress.com/_mNRhDn2.
Looks like the same as the throttle wiring (color and pins) but have no datasheet
Unfortunately there is no chance to talk with the Chinese .

 

[scrambler]

These are copies or licensed TMM sensors originally made by IDbikes

Sensors

IDbike develops and produces components for electric bikes, such as torque sensors, controllers and displays.

idbike.com

They are rear axle torque sensors, and these require the frame to match the sensor mounting, so not trivial. they also would not work on a mid drive bike as the motor usually goes thru the same chain as pedaling and so it would create a loop pedal effort activates sensor that activates motor that activates sensor even more and that never stops...

On a mid drive, the best torque sensors are normally Bottom bracket sensors.

What type of bike do you have and what type of motor / drivetrain?

 

[BullitRadu]

These are copies or licensed TMM sensors originally made by IDbikes

Sensors

IDbike develops and produces components for electric bikes, such as torque sensors, controllers and displays.

idbike.com

They are rear axle torque sensors, and these require the frame to match the sensor mounting, so not trivial. they also would not work on a mid drive bike as the motor usually goes thru the same chain as pedaling and so it would create a loop pedal effort activates sensor that activates motor that activates sensor even more and that never stops...

On a mid drive, the best torque sensors are normally Bottom bracket sensors.

What type of bike do you have and what type of motor / drivetrain?

Thanks for the answer. That data sheet is helpful. I can make the sensor fit but the mechanical calibration will be a pain in the ass.
my bike is a Larry vs Hary Bullit ( cargobike) on with I have mounted a 350w front hub gear ed .I don't have to much info about controler tho is very simple. Has pas,light and display out on wich it has brake and throttle . I will open the controler box to take some some pictures of it

 

[scrambler]

Are you saying the only motor on the bike is a hub motor in the front wheel?

If so then you may be could use a Bottom bracket Torque sensor, that would be much better than the frame mounted torque plate.
And if the controller has a PAS input (likely for a cadence sensor), you may be able to connect the Cadence info from the Bottom Bracket torque sensor, as these sensor have both Torque and cadence output.

PAS/Torque Sensors - Ebike Parts - Shop

Options to add automatic pedal assistance to engage the motor on your bike.

ebikes.ca

 

[KylerLaird]

I cobbled together a 20" fat tire kid e-bike years ago years ago. I used a front hub motor and a torque sensor. I ran it with a VESC. It was awesome! Step on the pedal and go - no hesitation. Stop pedaling - decelerates hard. The bike is way too small for me yet it was a delight to ride.

I have since bought a Lectra XP to toss in my plane. I have hardly used it. I took it out on the pasture last week to herd a reluctant Longhorn. The pedal sensor drove me crazy. It is terrible for anything but basic riding.

I highly recommend using torque sensors. I haven't tried using the cadence sensor for gating it. Seems like a safe thing to do, but I might miss the instant burst of power. I do think about having the cadence maintain power to the motor even when there's negligible pedal torque.

[I finally got a battery that I can mount to that little Mongoose frame so I'm trying to revive that bike now. I'm reading up...]

 

[PedalUma]

I cobbled together a 20" fat tire kid e-bike years ago years ago. I used a front hub motor and a torque sensor. I ran it with a VESC. It was awesome! Step on the pedal and go - no hesitation. Stop pedaling - decelerates hard. The bike is way too small for me yet it was a delight to ride.

I have since bought a Lectra XP to toss in my plane. I have hardly used it. I took it out on the pasture last week to herd a reluctant Longhorn. The pedal sensor drove me crazy. It is terrible for anything but basic riding.

I highly recommend using torque sensors. I haven't tried using the cadence sensor for gating it. Seems like a safe thing to do, but I might miss the instant burst of power. I do think about having the cadence maintain power to the motor even when there's negligible pedal torque.

[I finally got a battery that I can mount to that little Mongoose frame so I'm trying to revive that bike now. I'm reading up...]

This bike came back in for maintenance today. It has both a torque sensor and a cadence sensor. They work together. When you pedal faster by down shifting while also increasing pedal pressure, it gives you more. I did the connections thru-frame.

 

[scrambler]

What controller are you using to do the combination of torque sensor?