i was going over this thread because i lost one of my controller drawings when we moved to oregon, and i took the time to follow it through. many thanks to fechter for the great work...
i am installing my new cycle analyst, and ran into a couple of things i thought would be worth passing on. for those not familiar with this new version of the drainbrain, check it out at ebikes.ca...
besides adjustable speed and current limiting, new features include an automatic gain switching circuit that permits much more accurate measurement of low power levels.
the speed and current limiting are achieved by pulling down the throttle signal by the cycle analyst. the new controllers justin is selling have the connector installed, but for those of us who want to add them to existing controllers, it is quite simple. you conect wires to the B+, Ground, both ends of the sense resistor, and a hall sensor connection is provided for hub motors to eliminate the need for a speedo magnet. for folks like me with a freewheel system a speedo magnet can still be used.
the reason i thought this belonged in this thread is a discussion of how the limiting is achieved. the KA3525 pwm chip in these controllers is used in a somewhat non-standard configuration. the regular pwm input of the chip is not used at all. all control is done via the soft-start capacitor input. this thread has previously discussed how changing the value of this cap can change the "attack" time of the throttle.
the cycle analyst just pulls down the throttle signal to achieve limiting, like fechter's adjustable current limiting system. in the crystalite controllers we have, the ebrake input does basically the same thing, and is tied to the soft start input through a diode that only lets it pull the signal down. the control signal from the cycle analyst can thus be connected to the ebrake line, since it is a linear control line. the latest controllers are different, but i doubt any of us has seen them yet.
using the ebrake line as the speed/current limiting input has some advantages; most of us have that line run up to the handlebars anyway for the ebrake, and it can be connected to the limiting control signal there, providing an easy place for a speed limiter disable switch. you can change the limit parameters via the software, but that takes time and lots of keystrokes. a simple switch connecting the limiter signal to the ebrake signal can be mounted where it is easily accessable, permitting instant enable/disable of the limiting functions.
some of you may see where i am going with this. suppose we don't want anyone else riding our bike beyond a certain power/speed level. we just need to make the switch a bit difficult to operate if one does not know the secret. suppose i need to prove to someone who thinks my bike was going too fast that it will not go that fast under power? i might put a hidden NC reed switch in a position where an easily removed magnet enables speed and power limiting, so that i can just pull off the magnet and the bike is suddenly legal
an aside; neither Justin nor I would encourage anyone to operate an ebike in an unlawful manner.
I'll let ya know.
