Sunday, August 17, 2008

Belktronix Controller is Here

Last Thursday I received a FedEx package from Belktronix. It looks like the controller, contactor, potbox and integrator unit all showed up.

Here's the pile of parts that I received. I'm not entirely sure what the roll of black padded foam is just to the right of the main motor driver. The contactor is in the upper center with the potbox to the lower right and the integrator unit to the upper right. A small bag of mounting hardware (bottom center) also came with the system. Belktronix said that the charger/DC-DC unit and battery monitors for the AGM 12V batteries will arrive in another 3-4 weeks.

Here's a closeup view of the integrator circuit board. It looks like there's a comparator on the left, a bunch of transistors and several opto-couplers. A big red power resistor with measurement thermocouple under it exists on the right edge of the board. The four black blocks at the bottom of the picture are relays.

Here's another picture of the Belktronix integrator module (the "brains" of the controller).

The contactor has a 48V coil and looks smaller than the typical SW-200 contactor used in many DC EVs today.

Here's an inside view of the potbox. In order to prevent wear on any potentiometer, the Belktronix system uses an optical detector to detect pedal position. The optical transmit/receive sensor is the black box on the far right of the board. A chip in the center drives a PWM (pulse-width modulated) signal back to the integrator. Both the integrator and potbox have a resistor mounted in a socket, perhaps for easy replacement if it tends to blow.

Here's the underside of the potbox cover. The plunger on top is actuated by the accelerator pedal and a piece of white reflective tape on the bottom provides a surface for detection by the optical sensor. I really like this design because you can put it directly under the accelerator pedal and not worry about special cabling. It's optical-based design also prevents any mechanical potentiometer from wearing out.

I'm still a beta-test candidate for the Synkromotive controller, so hopefully I can test both out and see which is better.


Theo said...

Awesome blog, I hope it gets a lot of press!
Pardon my ignorance, but since you are going to connect the motor to a manual transmission, how do you plan to limit the RPM when in neutral or when the clutch is pressed? When in neutral, the motor will quickly spin to its maximal RPM, potentially up to self destruction. The thing is to make the controller aware of this situation so it can cut off the power when no resistance is applied to the motor. Or you can simply limit the max velocity through the controller, but then the motor will drain the batteries at 5500RPM every time it spins freely, such as in neutral.

TimK said...

Hi Theo. The motor actually doesn't spin at all unless the driver presses the accelerator pedal. I would definitely like to add an RPM sensor to the motor to shut off the controller if the RPM gets too high, but most careful EV drivers will simply not press the clutch or shift to neutral while also pressing on the accelerator. No current is pulled in neutral as long as the driver doesn't press the accelerator pedal. Electric motors don't "idle" like gasoline engines.