Beta CA build for R/C controllers

[justin_le]

Sorry for the belated beta-testing report, but I finally got around to running my CA-LRC last week on my Hunter EV Prize race bike.
( Hunter Valley EV Prize thread). I just used a single shunt.
Worked beautifully first go. I plugged in similar numbers to Adrian, and basically ran with that in the race. I really only had five laps of practice, so I didn't change any parameters before the race.

Hey excellent work and congratulations on the build! Anyways I'm sorry too for having left this thread hanging for so long. But trust that it's all for good cause.

I didn't mention yet but I did change the low voltage cutoff to have a 0.1V resolution as Kepler suggested earlier, and made a few other small tweaks at the end of summer which are in the Beta3 V2.24 firmware that is still available as a CA-LRC device for those wanting to experiment. However, the lively discussion, positive testing feedback and extended interest here confirmed that it was time stop this development dead in the tracks and instead opt for a complete redesign of the CA circuit to accommodate all the potential stuff we'd like to do with it rather than keeping hacking onto the existing design. So the last few months have been heavily involved in creating this:

Beta Rev12 of CA PCB with additional I/O ports

CA Rev12 PCB2.jpg (61.29 KiB) Viewed 1368 times

There's now a dedicated thermistor input for measuring (and scaling back power) based on motor temperature, a bidirectional communication port so that firmware can be upgraded with bootloader via any computer with a serial or USB port, a separate dedicated throttle input (independent of the auxiliary voltage input) so you can have on-the-fly current limit adjust and throttle control at the same time, a newer microchip with several times the memory and processing power, a PAS input for measuring pedal cadence in addition to wheel speed, and most fun for me is also a torque input that is compatible with the THUN torque sensing bottom bracket. So in addition to being able to implement a torque based pedal assist feedback mode, we can also calculate and show the human pedal power going into the cranks:

Pedal Power

CA 2.5 Pedal Power.jpg (22.79 KiB) Viewed 1368 times

I dunno about others here, but I've always been dying to see just how many watts my legs were adding to the mix when riding an ebike.

Anyways it's probably another 8-12 weeks of coding, testing, and redesigning before being ready for a next round of beta releases based on this new board layout and micro. But I just wanted to give a heads up to all those following this thread that that is where the project is going so you know what's up.

Thanks again for everyone here who has been a part of this. -Justin

[Miles]

most fun for me is also a torque input that is compatible with the THUN torque sensing bottom bracket. So in addition to being able to implement a torque based pedal assist feedback mode, we can also calculate and show the human pedal power going into the cranks:

That's great.

Presumably, you're going to stock the Thun sensored BBs?

[johnrobholmes]

Yes!! What a winning redesign! Can't think of anything else we would need added right now, great job!

[justin_le]

I have converted one of my K-force 100A esc's for direct connection to the CA. It gets a bit tight soldering the shunt directly to the ESC circuit board as Justin did with the CC160 esc so I decided to fit the shunt half way along neg cable.

Hey Kepler, that is a superbly slick sway to do the wiring mod and gives the controller a tidy "direct plug-in" functionality that has the appearance of being factory made for the purpose. Nicely done.

I only used one of the supplied shunts rather then paralleling 2 shunts together. This setup will only be used at around 30A and I figure one shunt should be fine up to 50A without a problem. This means the CA shunt value will be set to 1.4 mohm.

Just bear in mind that the shunt resistances average about 1.4 mOhm, but can sometimes be as low as 1.1 mOhm so you'll probably want to do a more precise calibration on them at some point. The easiest way to do this on the bench is to force a known current through the shunt by wiring up a constant current power supply with the (-) side on one of the controller phase leads, and the (+) side on the negative battery lead of the controller. That will force a current through the shunt via the mosfet body diodes. Then use a multimeter to measure how many mV are between pins 3 and 4 of the CA-DP cable, and your RShunt is mV / A.

Or you can just ride the bike for a bit both with the CA and some other calibrated Ah meter and compare the amp-hours, and scale RShunt such that they will match.

Over winter we'll be working on a jig for grinding slots in the shunts so that they can all be exactly calibrated to an identical value prior to shipping.

Justin

[panurge]

What awesome improving!!!!!!!!

I was just with the CA-LRC and the HV 160 in my hands thinking on a good-net way to setup the shunt sensor when I see the thread active!!!!!!

I was thinking about a way to do a setup for the CA-shunt and the Castle CapPack along the wire.......viewtopic.php?f=2&t=33268&p=483605#p483605

Have you guys Any suggestion?

Thanks Justin for your efforts.....

Jules

[justin_le]

I was thinking about a way to do a setup for the CA-shunt and the Castle CapPack along the wire.......viewtopic.php?f=2&t=33268&p=483605#p483605

Have you guys Any suggestion?

That should be pretty straightforwards, just add the shunt inline with the black lead much as Kepler did, and seal the whole shunt+cappack with a piece of heatshrink to keep it looking tidy:

Shunt on Controller.jpg (31.31 KiB) Viewed 1511 times

-Justin

[justin_le]

Presumably, you're going to stock the Thun sensored BBs?

Hoping so, just sent an inquiry to Thun last night. It does mean that people wanting to use this have to drill a small hole in the BB shell of their bike to feed the sensor wire through and then crimp on their own connectors, but given the level of hardware hacking that goes on here that shouldn't pose much of a problem. -Justin

[mrbill]

I dunno about others here, but I've always been dying to see just how many watts my legs were adding to the mix when riding an ebike.

As someone who comes to e-biking from the sport/fitness side, I can say that I've always been interested in seeing how power is allocated between the motor system and human pedaling. For many years I've used a PowerTap rear hub, and I've found it invaluable for measuring my own performance and for standing in as a makeshift dynamo on the bench to measure motor system efficiency.

The sport/fitness world seems to be moving toward the ANT+ standard of interoperability for power meters. Various designs (e.g. rear wheel (PowerTap), bottom bracket (Ergomo, THUN), crank (SRM, Quarg), and pedal axle (Garmin Vector)) are wireless devices (2.4Ghz) and log data wirelessly to a head unit (such as a Garmin GPS device or proprietary head unit) that logs other performance parameters such as speed, cadence, heart rate, altitude, location (using GPS), that can subsequently be correlated and uploaded to a PC or Mac for further analysis. Have you considered adding ANT+ compatibility so that a variety of power-measuring devices could be used?

Those of us using bottom bracket motor drives would have to use crank-based or pedal-based torque sensors to isolate human-only power. Bottom bracket or rear hub torque measuring devices will only show combined power.

[www.recumbents.com]

Justin,

I'm very interested in the Thun hub, please let me know the price when you get it. And of course your new RC CA! I just bought one and will be using it soon, but I may need to buy another when the new one is available!

-Warren.

[nicobie]

This is really good news!

The new add ons will cover every thing I need a bike monitor to do. The pedal torque sensor sounds intriguing, I'm almost afraid to find out just how much I'm contributing.

Will you be stocking a temp probe? Or will the CA be adjustable for any probe?

It looks like I need to start saving for the new model.

[Miles]

Those of us using bottom bracket motor drives would have to use crank-based or pedal-based torque sensors to isolate human-only power. Bottom bracket or rear hub torque measuring devices will only show combined power.

Bill,

The Thun system measures the torque transferred through the axle from the left pedal. With a Cyclone type BB drive, it should only register human power, I think.

[mrbill]

It does mean that people wanting to use this have to drill a small hole in the BB shell of their bike to feed the sensor wire through and then crimp on their own connectors, but given the level of hardware hacking that goes on here that shouldn't pose much of a problem.

Perhaps not, but drilling holes into a frame anywhere will weaken it. A video on Thun's web site shows that in 2012 they will be coming out with an "X-Cell RT 2.0" with wireless transmission. No indication if this will be Thun-proprietary or ANT+ compatible.

http://www.youtube.com/watch?v=EXS1pGaMOeg

[mrbill]

Those of us using bottom bracket motor drives would have to use crank-based or pedal-based torque sensors to isolate human-only power. Bottom bracket or rear hub torque measuring devices will only show combined power.

Bill,

The Thun system measures the torque transferred through the axle from the left pedal. With a Cyclone type BB drive, it should only register human power, I think.

Depends on the attachment. My first Cyclone drive was to the left crank. StokeMonkey also attaches to the left crank. Both systems force the pedals around when motoring, for better or worse. A right-crank or "4th chainring" motor connection would have the Thun (or Ergomo) measuring only left leg torque. Calculating power from one leg and multiplying by 2 increases system error due to uneven leg strength.

There's room for value in this space. Most of these torque-measuring/power devices are in the range of $1000US or higher (although Ergomo is running a sale on their 2007 model, $400US). What is the cost of a Thun BB?

[Miles]

A right-crank or "4th chainring" motor connection would have the Thun (or Ergomo) measuring only left leg torque.

Which is all it can do, anyway.....

There's room for value in this space. Most of these torque-measuring/power devices are in the range of $1000US or higher.....

I was thinking the same. I'm surprised that Thun haven't done it...

[liveforphysics]

In a frame that is well suited towards the loads and abuse an Ebike endures, drilling a small hole on the bottom bracket shell will have no effect. Round holes don't create focused stress riser points, so they do very little to structural integrity.

[panurge]

I was thinking about a way to do a setup for the CA-shunt and the Castle CapPack along the wire.......viewtopic.php?f=2&t=33268&p=483605#p483605

Have you guys Any suggestion?

That should be pretty straightforwards, just add the shunt inline with the black lead much as Kepler did, and seal the whole shunt+cappack with a piece of heatshrink to keep it looking tidy:

Shunt on Controller.jpg

-Justin

Beautiful.....thanks a lot for the picture.....

I think the thermistor is another great feature......as the separated throttle.......

Regards

Jules

[amberwolf]

So...would you do trade-ins of old CAs to get a price break on the new version?

Cuz it would be nice to be able to have a BionX-like system but with *real* power behind it. That's what I originally wanted to do with CrazyBike2, but never got a working pedal-torque sensor going, plus all the circuitry to parallel that with a throttle control on the brushed controller I was using then.


BTW, a quick google for the Thun sensor itself foudn this tidbit:
http://www.aliexpress.com/fm-store/6055 ... ensor.html
whcih appears to be controller, pedalec sensor and Thun sensor all in one package for only $160 for 5 sets. Buuut...given the way things usually work out, it probably does not include anything but the controllers. Anyway, it did find a pic of the sensor:


I'm having trouble finding places that actually sell the Thun sensor itself, or at least, that show a price for them. That probably means they'll be out of budge range for a lot of people (including me).

Hopefully I'll be able to come up with some other sensor input that can do the same type of output range for input that the Thun does, so the new CA can still be used to control things based on it.

[www.recumbents.com]

The Thun only shows torque from the left pedal? Um, maybe it's not such a good thing then, and only good for telling if the rider is pedaling.

[johnrobholmes]

You could "cheat" the thun being used as a pedelec control by jumping up and down on the bike I love it

[justin_le]

You could "cheat" the thun being used as a pedelec control by jumping up and down on the bike I love it

Indeed, in my first playing around with a THUN unit earlier in the year I was only using one of the two pulses from the cadence encoder, and there was literally no way to prevent pedalec mode from kicking in if you are standing on the pedals left foot forwards. Any slight rocking back and forth looks to the system like you are pedaling with massive force. Proper use of quadrature input solve that

It was also neat to see how much negative torque is applied across the spindle in the course of routine pedaling, where the action of the right leg pressing down does the work of lifting up your left leg. I suppose it's more efficient use of leg muscles to push down rather than to lift up? Interestingly you wouldn't see any of this left<->right pedal play with a strain sensor on the chainring. So even though that would properly show the net power of both legs getting to the wheel, it doesn't show the percentage of torque from one leg that is being absorbed by the other leg rather than being transmitted to the chain.

Anyways, I did hear back from THUN and they're pretty interested to see an ebike display and interface compatible with their sensor, and seem keen to help us make that happen. The pricing is reasonable enough that we'll probably stock them by Jan/Feb of next year and be able to offer a THUN + CA bundle in the $330-$350 price range. I suppose it's a bargain compared to existing bicycle power meters (mostly >$1000 as has been mentioned here), though may seem a bit pricey if all you want is to add pedalec functionality and don't care so much about seeing human wattage.

There are 5 different spindle lengths to choose from with the THUN BB, anybody have an idea on the distribution of spindle lengths in ebike usage?? I've never had consider this question before.

BTW, a quick google for the Thun sensor itself foudn this tidbit:
http://www.aliexpress.com/fm-store/6055 ... ensor.html
whcih appears to be controller, pedalec sensor and Thun sensor all in one package for only $160 for 5 sets. Buuut...given the way things usually work out, it probably does not include anything but the controllers.

That's correct, it's a china trader selling controllers only, the use of the THUN image and name is pretty inappropriate. It also looks (judging from the cable pinouts) like it probably is just using the THUN bottom bracket for cadence sensing, rather than for actual pedal torque.

-Justin

[justin_le]

Will you be stocking a temp probe? Or will the CA be adjustable for any probe?

Currently implemented as a 16 step look-up table with linear interpolation to use a familiar and inexpensive 10K NTC thermistor. But the generic use of a look-up table means that it could be setup to map pretty much any sensor's input/output curve. So if there are other things that people would want to use that channel to measure (like barometric pressure, "G" force meter, etc.) they could set up a mapping table and load that into the CA's eeprom and it will scale things accordingly. Well that's the idea at least.

-Justin

[Dingo2024]

There are 5 different spindle lengths to choose from with the THUN BB, anybody have an idea on the distribution of spindle lengths in ebike usage?? I've never had consider this question before.

Hi Justin,

not sure on the distribution of spindle lengths but if looking at cyclone type setups then the axle length is 152mm to allow crank arm clearance with the motor (and it is all biased to the non drive side)

Q: do you know if they are only available in square taper or also ISIS fitment?

hope this helps and good luck with it all,


Ian

[mrbill]

There are 5 different spindle lengths to choose from with the THUN BB, anybody have an idea on the distribution of spindle lengths in ebike usage?? I've never had consider this question before.

Hi Justin,

not sure on the distribution of spindle lengths but if looking at cyclone type setups then the axle length is 152mm to allow crank arm clearance with the motor (and it is all biased to the non drive side)

Q: do you know if they are only available in square taper or also ISIS fitment?

hope this helps and good luck with it all,


Ian

I've used a variety of spindle lengths on my bikes, usually with an offset to one side or the other. One of my bikes uses 145mm spindle with full-right offset. To my knowledge only Phil Wood (who happen to be a near me) offer custom-length and custom-offset bottom brackets. The standard sizes probably work well for bikes with hub motors, but it would be nice if Thun offered a good range of lengths and if the offsets could be adjusted by the user or dealer.

[justin_le]

Hi Justin,
not sure on the distribution of spindle lengths but if looking at cyclone type setups then the axle length is 152mm to allow crank arm clearance with the motor (and it is all biased to the non drive side)

Hmm, didn't realize that the Cyclone system requires an extra long spindle. The options with THUN appear to be 120mm, 128mm, and 136mm, with the 120 and 128 options available with two different offsets (L and K). Dimension sheet is attached if anyone can make too much sense of it. I suppose it makes sense to err on the side of getting the longer lengths?

Q: do you know if they are only available in square taper or also ISIS fitment?

Looks like square taper only at the moment.

-Justin

[Dingo2024]

Hi Justin,
not sure on the distribution of spindle lengths but if looking at cyclone type setups then the axle length is 152mm to allow crank arm clearance with the motor (and it is all biased to the non drive side)

Hmm, didn't realize that the Cyclone system requires an extra long spindle. The options with THUN appear to be 120mm, 128mm, and 136mm, with the 120 and 128 options available with two different offsets (L and K). Dimension sheet is attached if anyone can make too much sense of it. I suppose it makes sense to err on the side of getting the longer lengths?

Q: do you know if they are only available in square taper or also ISIS fitment?

Looks like square taper only at the moment.

-Justin

ok had a quick look at the spec sheet....and it looks to me that the offsets are all on the right side (L2) ie drive side which would not help on a cyclone setup. This I guess is more for chain alignment on regular single, two and three chinring setups. That said I have spoken with the cyclone dealer in the UK and he assures me that their sytem (3 chain wheel) will work with a regular length bottom bracket no problem and has run this on his demo bike for months. (this was an ISIS BB though and could 'push' the cranks out a little further)

EDIT; this is from the cyclone tw site ........so 128mm works for ISIS

http://www.cyclone-e-bikes.tw/product.p ... _show=3235

also in 140mm flavour;

http://www.cyclone-e-bikes.tw/product.p ... 03&count=1

my guess would be the longer sizes of Thun would be fine

Ian