BEAMts Torque Sensor...Figured it out!

A

Avitt

100 W
Joined
Jan 2, 2014
Messages
264
Location
Orange County, CA
I'll preface this by saying that I don't use a throttle, and I've been pretty happy with the Torque Simulation PAS mode on my bike:

http://endless-sphere.com/forums/viewtopic.php?f=6&t=58335

But I've been itching to try a true torque sensor, to overcome a couple of small shortcomings of the PAS. Namely,

  • Takeoffs can take a half pedal rotation before the assist kicks in. The bike is heavy, so this typically requires downshifting at stops.
  • The speed for the PAS is largely determined by the 5 assist levels. There's not much response based on the pedal speed.
  • When I want to punch it, I either have to step though the PAS levels, or I am limited to the +200W or so that my legs can contribute.

My options for a torque sensor are limited. I can't use a BB sensor, because I have a Patterson Metropolis Transmission two-speed crankset. So when I came across the BEAMts sensor from Santa Monica Electric Vehicles, I was eager to give it a try. Unfortunately, they're not so available, and it took me about 6 months to track one down (thanks to a reference by member green79): http://www.usaebikes.com/shop/beamts-pedal-assist-torque-sensor

This is the Prodecotech version, which is wired to plug and play with their bikes. It comes with a bottom bracket mount. So the wiring and the mount would have to be adapted for my bike.

One of the nice features of this torque sensor is the way that it does not require a Cycle Analyst to interpret the signal. Instead, it outputs a throttle level signal, which can be fed directly into any controller. The Prodecotech version of the BEAMts has a pass though connector, which allows you to plug in your throttle. (This was nice for me, because I use the throttle voltage to trigger a relay which controls my lights.)

It took me a while to figure out the wiring. There are three connectors:

  • 4-Pin Male Connector - To Controller
    • Red: +5V
    • Blue: Ground
    • Green: Signal
    • Yellow: Pass through from battery (used to power battery-level LEDs on Prodeco bike)
  • 4-Pin Female Connector - From Throttle
    • White: +5V
    • Gray: Ground
    • Pink: Signal
    • Yellow: Passthrough from battery
  • 3-Pin Male - Programming Port
    • Brown: Ground
    • Blue: Tx
    • Yellow: Rx

I had to change the gender, and convert the 4-pin to 3-pin connectors. Then it plugged right into my controller...And worked!

The mount had to be adapted to work with the Metropolis Transmission. My solution was to cut the bracket, and mount it to the back of the Metropolis body, using two holes from a non-used inner chainguide. There wasn't much room to work with, but everything ended up fitting perfectly. I replaced the provided nylon roller with a Shimano derailleur pulley:

5ZdrRe.jpg

mquc6W.jpg


So everything was installed, and working. But I found the that the power was coming on too quickly for my front drive setup, and I was getting some wheel spin. So I went about trying to figure out how to program this thing. Britt Jackson of SMEV provided credentials to access their support site, http://www.beamtssample.com/, where I was able to download the Windows based sensor setup program. But I had no idea how to connect the sensor to the PC.

After a couple of unanswered requests to purchase a programming cable, I decided to try to put something together myself. I remembered that I had an FTDI serial to USB interface cable, (which I'd purchased with my Juicebox EVSE). I downloaded the FTDI drivers, fashioned a cable, and found out which one of the 3-pin connector wires was ground. The other two wires had to be Tx/Rx, so it was just a matter of plugging and playing...

n834ic.jpg

RbBzSO.jpg


Once in the setup program, I set the ramp-up delay to maximum (to eliminate the wheelspin), and set the minimum and maximum output levels to match the input levels of my controller. Here are my settings:

vccKw7.jpg


If anyone want to go down this path with one of these torque sensors, here are a few references to help:

Prodecotech Installation Video: https://www.youtube.com/watch?v=dhTecotFNc8
Programming Instructions: http://www.king-meter.com/upload/files/BEAMts GUI 3.rar
FTDI Programming Cable: http://www.emotorwerks.com/products...cable-for-arduino-juicebox/related_product-44

It's going to take me a few days to get a good impression of the sensor, how it works by itself, and how it overlays on my existing PAS system. I'll be back in a while to provide feedback.
 
Thanks for the post, I was interested in this unit at one time.
 
Nice work! I like the combo of the Patterson and idler based torque sensor. Do you have a cadence sensor as well as the BeamTS? How easy would it be to get this to work with a CA V3? I'm interested in hearing more about your experience - I just installed a Thun but was wondering if this would be a more responsive system.
 
green79 said:
Nice work! I like the combo of the Patterson and idler based torque sensor. Do you have a cadence sensor as well as the BeamTS? How easy would it be to get this to work with a CA V3? I'm interested in hearing more about your experience - I just installed a Thun but was wondering if this would be a more responsive system.
Click to expand...

Thanks!

I think this could easily made to work with the CA V3, as it feeds into the throttle input. But you would loose the ability to set the torque sensor parameters through the CA, and would have to use the BEAMts interface.

I've had to make a few tweaks to the settings above, to smooth out the operation. I found that the maximum voltage was set too high, and my controller would temporarily shut down after about 5 seconds of 4.0+V input. I resolved this by lowering the maximum torque sensor throttle output to 3.8V.

I also noticed that the pedal strokes were not smooth, but the left and right pedals felt disconnected. After some trial and error, I found that this problem went away by lowering the "Sleep Time" parameter to 0 seconds. My new settings look like this:

tp9qXm.jpg


I am using a combination of cadence and torque sensors, which I think is the best possible pedelec configuration. I'll use the following crappy drawing to illustrate some of the benefits of this combination:

jGVC4P.jpg


  • 1) Takeoff from stop is improved. With the cadence sensor alone, there is some delay before the power comes on. Since my bike is fairly heavy, this means that I need to drop down a few gears before coming to a stop, particularly when going uphill. With the torque sensor, the power comes on as soon as I apply pressure to a pedal. So being in a lower gear is no longer important.
    2) Once underway, it can take quite a bit if physical effort to maintain the speed I prefer (25-30 mph) with the torque sensor alone. So I'm happy to have the contribution of the cadence sensor. When the cadence sensor kicks in, it will maintain the power level at the preset level. I can use the PAS levels to select how much effort is required to maintain the desired speed...More or less, depending on how much exercise I want.
    3) The torque sensor allows me to vary my speed upward from the PAS level baseline. Before having the torque sensor, I could only increase the speed by stepping up the PAS level, or by pedaling much harder.
    4) The torque sensor makes it much quicker and more intuitive to reach maximum speed. Hammer the pedals, and I'm through that intersection...

So far, I think that this is the best possible combination for achieving a natural pedelec feel. My objective was to make a heavy, relatively powerful ebike ride as much as possible like a lighter, conventional bike...I think it's about as close as I can come (without spending a whole lot more money, anyway).

In general, after just a few days of use, I don't think I prefer the torque sensor to the simulated torque PAS mode of the BMSBattery controller. But the combination of torque and cadence inputs is significantly superior to either sensor alone.
 
I sent some pictures and questions to Britt Jackson, of Santa Monica EV. He noticed that my setup lifted the chain much higher than the recommended 5-6mm. He said that the effect of this is to apply too much pre-tension on the sensor, which limits its dynamic range, and makes the response seem a bit jerky and abrupt. Britt was kind enough to send me a couple of alternative brackets to try.

I ended up changing the bracket, and switching from the sprocketed pulley to the nylon roller (because the roller has an effective diameter which is about 10mm smaller). The chain is now much lower:

BBhaJw.jpg


The difference it quite noticeable, particulary on takoffs, which are now much more gradual and without wheel spin. Also, pedal strokes are more "fluid", and feel linked together, instead of like individual pulses.
 
I just put together an ebike with an EEB frame, Max-E, modded MXUS 3kw/4t, and a 420 cell 18650 battery pack (21s20p, 78v/58ah) and took it around the lot for the first time tonight. I'm using a half-twist throttle wired to the passthrough on the BeamTS unit, which is connected to my adaptto controller.

The throttle voltage behaves unusually when connected to the BeamTS though. It oscillates up and down ~.4v, enough to make the bike surge on/off more than I'd like it to. I'm using throttle smoothing, and taking advantage of the throttle limits and exponential scaling to reduce the effect but it's still too much.

The interesting and frustrating thing is, when I use the BeamTS alone, the output is perfectly steady. Both are transmitted from the same unit, to the same controller-- but one input is coming from throttle passthrough.

I'll contact them and see if they can comment, otherwise I'm open to suggestions.
 
Avitt said:
One of the nice features of this torque sensor is the way that it does not require a Cycle Analyst to interpret the signal. Instead, it outputs a throttle level signal, which can be fed directly into any controller. The Prodecotech version of the BEAMts has a pass though connector, which allows you to plug in your throttle. (This was nice for me, because I use the throttle voltage to trigger a relay which controls my lights.).
Click to expand...

Sorry for reviving an old thread, but I am looking at getting an Ebike, and I cannot find one that has all the elements I need.

The best compromise I found so far uses an Adaptto controller which does not accept a torque sensor input, and I absolutely want to be able to use pedal assist with a Torque sensor (possibly combined with a cadence sensor for the very good reasons you outlined).

I am therefore extremely interested in the solution you described, But have a few questions regarding its implementation.

1- You say the Sensor can plug in the Adaptto throttle connector with a pass through on the existing throttle, but I am not 100% clear on something (sorry I am still new to all this).
I am trying to confirm that with that setup on the Adaptto, you can use both the torque pedal assist and the throttle at the same time? (which would be great as the video suggest)
And if so, if their inputs are added to each other or if it just takes the max from either one? (which would be the expected/desired effect)
What I mean, is that if the torque sensor outputs 2v, and I turn the throttle to the level where it outputs 4v, do I get 4 v in the controller, or 6v?

2- You said you were able to use both the cadence sensor and the torque sensor. Once you had the torque sensor on the throttle, was it simply a matter of connecting the PAS cadence sensor to the controller PAS input, or did you have anything special to do?
Does the merge of inputs from torque and cadence as described in your diagram occurs automatically? again, basically outputting the highest power request from either torque or cadence?

3- Did you add a switch to be able to turn off torque pedal assist when you only want throttle?

I truly appreciate if you can take the time to clarify these, as they would be a game changer for what I am trying to do .
Thanks!
 
scrambler said:
Sorry for reviving an old thread, but I am looking at getting an Ebike, and I cannot find one that has all the elements I need.

The best compromise I found so far uses an Adaptto controller which does not accept a torque sensor input, and I absolutely want to be able to use pedal assist with a Torque sensor (possibly combined with a cadence sensor for the very good reasons you outlined).

I am therefore extremely interested in the solution you described, But have a few questions regarding its implementation.

1- You say the Sensor can plug in the Adaptto throttle connector with a pass through on the existing throttle, but I am not 100% clear on something (sorry I am still new to all this).
I am trying to confirm that with that setup on the Adaptto, you can use both the torque pedal assist and the throttle at the same time? (which would be great as the video suggest)
And if so, if their inputs are added to each other or if it just takes the max from either one? (which would be the expected/desired effect)
What I mean, is that if the torque sensor outputs 2v, and I turn the throttle to the level where it outputs 4v, do I get 4 v in the controller, or 6v?
Click to expand...

Happy to try to help. First though, let me point out that I am using a KT S12S controller, not an Adaptto. Xenodius commented that he is using an Apadtto with a 78v battery, and was having trouble when using the throttle passthrough...You may want to check with him directly, to see if this issue was resolved.

I can answer that the output from the Beam TS will be the maximum of either the torque sensor output, or the throttle input. (So yes, you can use both at the same times, using the throttle to override the torque sensor.)

2- You said you were able to use both the cadence sensor and the torque sensor. Once you had the torque sensor on the throttle, was it simply a matter of connecting the PAS cadence sensor to the controller PAS input, or did you have anything special to do?
Does the merge of inputs from torque and cadence as described in your diagram occurs automatically? again, basically outputting the highest power request from either torque or cadence?
Click to expand...

This will depend on your controller. If the controller allows the simultaneous use of both PAS and throttle inputs (which is very probable), then you'll b able to combine the cadence and torques sensors, with the benefits which I've described.

3- Did you add a switch to be able to turn off torque pedal assist when you only want throttle?
Click to expand...

In my case, there is no need, since I don't have a throttle. (I only used one for setup and testing). If you want to add this capability, it would require some investigation...Cutting power to the Beam TS may cause a problem with the passed through throttle signal.
 
Thanks for the quick answers!

Avitt said:
Happy to try to help. First though, let me point out that I am using a KT S12S controller, not an Adaptto. Xenodius commented that he is using an Apadtto with a 78v battery, and was having trouble when using the throttle passthrough...You may want to check with him directly, to see if this issue was resolved.
Click to expand...
Thanks, will PM him and hopefully get a response.

3- Did you add a switch to be able to turn off torque pedal assist when you only want throttle?

In my case, there is no need, since I don't have a throttle. (I only used one for setup and testing). If you want to add this capability, it would require some investigation...Cutting power to the Beam TS may cause a problem with the passed through throttle signal.
Click to expand...

Good point, eventually it may require to have a switch on the throttle input signal to the controller, to either take it directly from the throttle, or from the torque sensor pass through.
 
I PMed Xenodius, and got the following answer below from him.

Xenodius said:
It turns out, I had mounted the sensor too high and it never was able to autocalibrate properly because slight pressure on the pedals fully depressed the chain roller on the sensor... according to Britt Jackson at SantaMonicaEV. I haven't had time to fix it yet since grad students in my program are expected to work 60-80 hours and science culture here is messed up, but I think he knows what he's talking about. I do know my Max-E is more than capable of powering both the BeamTS sensor, and two Wuxing throttles (ebrake/power) with less than 5mv voltage drop, so, I think it'll work fine once I get it adjusted properly
Click to expand...

This does sound hopeful for the BEAMts being a viable solution to Torque sensing Pedal assist on Adaptto :)
 
scrambler said:
I PMed Xenodius, and got the following answer below from him.

Xenodius said:
It turns out, I had mounted the sensor too high and it never was able to autocalibrate properly because slight pressure on the pedals fully depressed the chain roller on the sensor... according to Britt Jackson at SantaMonicaEV. I haven't had time to fix it yet since grad students in my program are expected to work 60-80 hours and science culture here is messed up, but I think he knows what he's talking about. I do know my Max-E is more than capable of powering both the BeamTS sensor, and two Wuxing throttles (ebrake/power) with less than 5mv voltage drop, so, I think it'll work fine once I get it adjusted properly
Click to expand...

This does sound hopeful for the BEAMts being a viable solution to Torque sensing Pedal assist :)
Click to expand...

Interesting response...That's the exact problem that I experienced, and documented above. So I'm pretty convinced that you'll be able to set up the Beam TS to work well for you.
 
Hello!
BEAMts Torque Sensor of mid motor Bafang bbs02 750w
compatible?

how to work better with the rear wheel of the motor or central motor?

Thank you!
 
BEAMts Torque Sensor of mid motor Bafang bbs02 750w
compatible?

how to work better with the rear wheel of the motor or central motor?

Thank you!
 
It won't work with a mid drive (other than to allow setting of instantly from a stop).

Once the mid drive applies power through the chain the torque sensor is sensing the mid drive power, not rider input.
 
For the BEAMts to work with a mid drive, you would need a separate chain ring for the motor and for pedaling.

If you only have one chain ring, then there is no way to differentiate the torque/effort coming from you pedaling and the torque/effort coming from the motor.

As you start applying pressure on the pedals, the sensor would detect pressure and ask the motor to provide assistance proportional to your pedaling pressure. As the motor applies additional pressure, the sensor would detect that increased pressure and therefore interpret that as needing even more assistance from the motor, so it would increase throttle again. This would go on and on rapidly, the system feeding on itself, until maximum assistance is provided.

This means your system would become like an on / off switch. As soon as you put even a light pressure on the pedal, it would escalate to maximum power...

Not good, and the opposite of what you expect from a torque sensor, which is to provide assistance that is proportional to the pedaling pressure :)

If you look at the SantaMonicaEV site, for Mid drive they use a two chains configuration
http://www.santamonicaev.com/page4/index.html
With such a system, you can have the BEAMts on the chain that is driven by the pedal. The motor using a separate chain to provide power to the rear wheel, it will not activate the sensor.
 
Any updates on the Beam TS?

No one seems to have them in stock, so I sent the OEM an email to acquire one for testing.
 
Whoops, sorry, missed that.
 
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