This may not be the right thread to post this under, and if so, I'll learn how to move it to a new/different thread. What I have is the following question:
Is it possible with the current CAv3 firmware/hardware to have a TORQUE ONLY sensor input setup? (i.e., no PAS info at all).
1. The ebike in question is a "Rowbike" (rowbike.com) prototype. Given it's architecture, it has no pedals (and no bottom bracket) used for propulsion. It uses a 'power lever' which has a cadence of sorts, but I don't want to monitor that, at least not yet.
2. The torque signal comes from four strain gauges I have mounted in a Wheatstone bridge configuration on the steel handlebars, which are pulled by the rider to create propulsion. The strain gauges are supplied by Justin, as he uses these in the same type of torque reading setup on his electric longboard (discussed on another thread here on ES). This part is working extremely well, thanks to wonderful support from Grin.
3. The electric assist is provided by a Crystalyte HT3525 rear hub motor radially laced in a 20" wheel. Power comes from a 48V (13S) eZee 10.5AHr Li battery pack, and is controlled a Grin Phaserunner (had been a Lyen). With Schwalbe Big Apple Plus tires, this setup is powerful enough to tow a car, so clearly my design suffers from overkill thinking.
4. The strain gauge low level signals are amplified/conditioned in either of the following methods while developing this prototype:
a) A "Grin Strain4" dual op-amp board designed and created by Justin for use in the StokeMonkey conversion kit, and used in other very interesting prototype projects he's doing; and,
b) a instrument amplifier based (INA122) board I and a colleague developed, which is a simpler amp than Justin's board because it ignores all of the PAS (RPM, Dir) parameters and voltage regulation. It also uses a dual op-amp to help get the output voltages into the analog throttle range needed.
Ideally, I would like to simply go into the CAv3's PASD (PAS Device) section, select a "Custom" device which would do the current voltage to Nm conversion just as it does now, and have the CAv3 send a standard throttle signal to the Phaserunner. I'd like for all of this to happen without any reference to PAS parameters. To get the 'human watts' values, I suppose I would take the Nm torque value, which represents how hard the rider is pulling on the handlebars/power lever, and combine it with the time over which the force is applied. This metric isn't critical to the project (yet).
When I take the output of the strain gauges and run it through our amplifier, I can tweak the amplifier's gain and voltage reference offsets to mimic a typical throttle range of about 0.85-4.00 volts, and use this setup as a somewhat standard throttle. However, I want to be able to continue using an actual separate dedicated throttle, and have my torque signal go into the TRQ (green) wire on the CA's PAS connector, and have the usual benefits of the CA's management abilities.
I'm hoping that I'm missing something obvious here, and don't really need to 'fake' a PAS cadence/pulse input to get a proportional assist based solely on the torque signal from my strain gauges. I'm pretty sure Grin has a way of accomplishing this, because I think that even as I type this (Jun 10), Justin is up in Vancouver at a "Main St" event, demo-ing a new version of his electric longboard which uses technology which I've been copying/mimicking/stealing all along, and I don't *think* he bothers with PAS data on the longboard...