EU "legaliser" for an RC motorised ebike

[bobc]

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.

[timpootle]

This looks interesting, not so much for the legalisation but more for drivability. I have ridden a couple of conversions now whose twitchy throttles made them almost unridable. Good work, Bob!

[bobc]

Thought I'd add a bit more info to this; the reason I did the circuit was for an electric assisted pedal trike.
I work with a school "greenpower challenge" team. Our car goes over 120 miles in a 4hr race on just 20p worth of electricity. I want that performance in my commuting vehicle.
And I've thought of a way to get it. EU rules let me electrify a trike with 250W motor power up to 25kph - and still call it a pedal trike with no tax, insurance, type testing, MOT etc. etc. I don't want a full fairing (even though that's the best for aero) because any screen you have to look through is dangerous unless it's made of glass & has wipers, squirters and demist. So - a partially faired open cockpit recumbent trike - that should be nearly as good as a greenpower car for aerodynamic efficiency.
Problem is that with a recumbent trike you need a massive box for the pedalling feet (size of feet + crank diameter + a bit) and that makes seeing the potholes an issue. There's still an answer; don't have a crank, have treadles (or a k-drive). So that's what I'm making.
I expect to use about 10Wh per mile at 15.6mph. Compared with a fairly efficient diesel car, that's a fuel cost reduction factor of about a hundred. That's epic. Plus there are practically none of the other car expenses either (fuel is less than half the operating cost of a car).
It all looks pretty positive;
1) you won't get hot/sweaty because of the electric - so you won't neeed a shower after getting to work
2) if you start to get cold - pedal (treadle) a bit ;^)
3) partial fairing keeps you warm/clean
4) do all the bike things (e.g. short cuts through parks etc)
5) maintain a respectable average speed (thanks to electric power you don't need to be bradley wiggins)
I've started making the trike as well. Unfortunately I'm not a bike builder so it will probably end up a bit heavy... I want full suspension too....

[bobc]

PCBs arrived last week - now built up. Just waiting for a programming adapter to arrive from hongkong ;^)

programming adapter finally here - wow that took a while! I Also needed to make an extra bodge board on the programmer to allow 1) use of tiny10 micro and 2) use of reset pin for purposes other than resetting.... All going now & electrification of my trike on-going as a test-bed ;^)

[bobc]

Bit of an update: programming solution here & working; Hardware (mostly) in place to motorise my trike. Only lack of time + inherent laziness holding me back........