EU "legaliser" for an RC motorised ebike
Posted: Wed Jan 30, 2013 1:16 pm
My ebike, (it's done several thousand miles now), uses a brushless outrunner and ESC from the model plane world an a small circuit to translate the output from a hall effect throttle to drive the ESC. This works fine but it's hard to drive (throttle way too twitchy) and technically illegal (it can deliver more than 250W, though max speed is voltage limited near the legal max).
I'm developing a better "small circuit" which will also place a shunt on the battery -ve lead and have a speed sensor input. This will make my arrangement legal in both speed and power. By tempering the demand to the ESC by the measured speed I can avoid the synch loss events and massive uncontrolled torques that make my present bike hard to ride. The battery current feeds back electric power usage and I can make that 250W (+ a bit for inefficiency) over the speed range (say) 4 to 15.6mph - i.e. I effectively have an electrical CVT. The "small circuit" design at present looks as though it will cost about £1 (2 active components, a single opamp and a ATtiny5 micro).
It should be an attractive package - suitable motors cost ~£25, an ESC ~£10. If it works well I'll make the design infomation available & get a few PCBs made (BTW the PCB is 2cm square & is simply supprted bythe wiring) and knock them out at cost to home constructors.
PCB design is done & I'm talking to a guy who'll develop the software tonight: should have results reasonably quickly.
I'm developing a better "small circuit" which will also place a shunt on the battery -ve lead and have a speed sensor input. This will make my arrangement legal in both speed and power. By tempering the demand to the ESC by the measured speed I can avoid the synch loss events and massive uncontrolled torques that make my present bike hard to ride. The battery current feeds back electric power usage and I can make that 250W (+ a bit for inefficiency) over the speed range (say) 4 to 15.6mph - i.e. I effectively have an electrical CVT. The "small circuit" design at present looks as though it will cost about £1 (2 active components, a single opamp and a ATtiny5 micro).
It should be an attractive package - suitable motors cost ~£25, an ESC ~£10. If it works well I'll make the design infomation available & get a few PCBs made (BTW the PCB is 2cm square & is simply supprted bythe wiring) and knock them out at cost to home constructors.
PCB design is done & I'm talking to a guy who'll develop the software tonight: should have results reasonably quickly.