Hello collective brain,

A while back, I asked about removing potting from a circuit, and my=20
attempt didn't work.  The circuit was a motor controller for an electric=20
bike.  I ended up salvaging some a heat sink, connectors and cables from=20
the controller, but otherwise it is now a shapeless lump of plastic and=20
components.

The bike was a thinkbike, manufactured by Ford motor company in the=20
early 90s.  It had a "thinbrain" on the handlebars with an 18 pin=20
PIC16C5x (54?) on it.  I've replaced the old PIC with a 16F88, and have=20
code that reads the Hall sensor throttle control and outputs a PWM=20
signal from 0 to 100% of full current.  The plan is to send this PWM=20
signal to a 24V, 400 watt, 555 based PWM controller that I bought.  I=20
would cut out the existing 555 controller on that board.

In case sending a 12 kHz PWM signal down 3 feet of 8 lead cable doesn't=20
work well, I would need to add another controller at the bottom end, and=20
wonder what would be a good candidate for a small simple board that I=20
can buy off the shelf for this.

* Communications protocol between the 2 boards is not critical.  The=20
current thinkbrain at the handlebar has 2 lines D0 and D1 that could be=20
used and they have resistor termination, one with a series 100 ohm.

* I would need 2 analog channels, as there are additional Hall sensors,=20
one for pedal torque and one for wheel speed.

The pedal torque mechanism was interesting.  I thought it was just a=20
pedal rotation sensor, but rotating the pedals produced no output.=20
Jamming the output gear and putting pressure on the pedal produces=20
output.  It has a planetary gear mechanism with a spring loaded outer=20
gear which, when torque is applied, floats enough to move two magnets=20
sandwiching a Hall cell.  I think someone on this list has worked with a=20
pedal torque sensor and I wonder how I might use this signal to vary=20
motor output.
The battery pack is another issue.  It is a 24V pack made of 2 12V, 12AH=20
sealed lead acid batteries.   There is a bq2013H gas gauge IC and a=20
PIC16C711 and a handful of resistors, caps, and transistors on the=20
circuit board.

I only want to get it running as a learning and demonstration exercise,=20
weatherization and reliability not really critical.

So, I'm looking for ideas on:
o Wisdom of sending PWM down 3 feet of cable, and alternatives.
o Usage of wheel speed and pedal torque signals on an electric bike.
o Experiences using the TI bq20xx gas gauge IC and talking to it with a uC.

Thanks group.

Joe Wronski


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