Death To All Controllers....

Ok, not ALL of them, but someone apparently sentenced mine. :(

Since it is made from a many-times-repaired Scoot'N'Go controller that started out it's life with me as already cooked *and* corroded, I'm not all that surprised. The issue this time is not in the power section, which I had upgraded last year to handle over 100 amps at 100 volts, using offboard-mounted MOSFETs and JFETs driving them (plus a diode pack for freewheeling currents). It is apparently the LM339 op-amp, probably internally shorted, as it drags down the supply voltage on it's side of the board to less than 3V.

All the other components are fine, except for one of the power resistors used in a voltage divider that provides the power to the LM339 section--it is burned open, probably from excessive current draw by the LM339.

I can't remove the LM339 and replace it without destroying the PCB, due to it's condition. It was not well-made to begin with, and what it went thru before I got it, causing burns and corrosion on it, would probably ensure that the copper will come off with the chip.

I *might* be able to Dremel off the chip by cutting it's legs, then carefully soldering a new LM339 in it's place by bridging from the legs to the PCB, but I am not confident it would work for long if it worked at all.

I am instead working on a version of the application note circuit for the Unitrode UC3637 PWM motor control chip, which is fairly simple. The big problem is that I have to do it on perfboard, at least at first, and I'm not sure how well that will work no matter how I beef up wiring, etc. If it all works out ok, I'll see if I can find the materials to etch a PCB for it if that would fix any issues I have with it, but I don't want to waste that kind of material if it doesn't work right to start with.

There are other motor control chips, such as the MC33035, which can also be adapted to brushed motor use (it's made for BLDC control), and I am slowly working on a design for that one that will let me use either kind of motor, with jumpers or switches for the configuration. It's not a "now" kind of project, though, and I need something right now to use with the motor on the bike.

Another thing still being worked on, hopefully integrated into this new controller, would be a version of that autothrottle controlled by pedal chain tension.

Yet one more thing to test is a converter circuit that would let me use a hall-based throttle on any controller, even one that requires a pot, by basically using the hall output voltage to control a digital pot. Then the digital pot wiper and terminals would connect in place of the pot throttle, and the hall throttle would connect to the controls of the digital pot (via some intermediate circuitry). It's actually pretty simple, but would probably cost more than just replacing whatever hall throttle someone has with a pot throttle. Still, if a non-replaceable hall throttle had to be used with a pot-based controller, like my autothrottle that has to be a hall sensor for environmental and mechanical-simplicity reasons, it would at least allow it to work!

Until I finish the controller and can test it, I may pull the motor and batteries off the bike so I can at least ride it around. I did patch the tubes sufficiently that at the moment it appears to be holding pressure, though I won't be confident of them until I can replace them with new ones (or at least used ones that don't have any holes in them!).