User Manual

Version 1.5 - December 11, 2010

inputs to the power chips not the actual output voltage. It is possible for the power chip to be

in safety shutdown while receiving an input signal. Thus it is possible for the LED to be lit

while no voltage is output from the power chips. Note, it is possible and often prudent to code

and debug the Arduino application with no battery connected to the MegaMoto using the LEDs

as visual indicators. The LEDs are powered by the Arduino outputs and do not require a

battery connected to the MegaMoto.

Jumper Connections

The MegaMoto uses jumpers to select which Arduino pins are used for all important functions.

This allows several MegaMoto units to be stacked on one base Arduino unit and be controlled

independently. The MegaMoto also cooperates well with other shields that might have hard-

wired pin assignments.

Enable Jumper: This jumper selects the Arduino pin used to enable and disable the

MegaMoto. There are four choices on this jumper block. One and only one jumper must be

placed on this block to choose the enable source. Logic HIGH enables the unit. Do not

attempt to drive the MegaMoto by pulsing the Enable input. This method of driving does not

work with these power chips.

Enable Jumper Connections

D13, D12, D8 Enable using one of these digital pins – set HIGH to enable

5V The MegaMoto is always enabled (see usage notes)

PWM A/B Source Jumper: The MegaMoto is designed to use the PWM outputs from the

CPU timer peripherals. Placing a jumper onto these blocks connects the input of the power

chip to the output of a CPU timer pin. The standard Arduino CPU is the ATMega328. This

chip has three hardware timers which control several digital output pins using the

AnalogWrite() library function. One and only one jumper must be placed on each PWM

source block to connect the power chip inputs to a CPU output. Note, the standard PWM

frequency (~500hz) provided by the AnalogWrite() function may be too low for many motors or

other loads. The CPU registers dedicated to the timer peripherals may be modified to

increase the PWM frequency. See the CPU datasheet for details on controlling the timer

peripherals.

PWM Source Jumper Connections

PWMA

D6 PWMA from pin D6 – Timer0 PWM0A

D9 PWMA from pin D5 – Timer1 PWM1A

D11 PWMA from pin D11 – Timer2 PWM2A

PWMB

D5 PWMB from pin D5 – Timer0 PWM0B

D10 PWMB from pin D10 – Timer1 PWM1B

D3 PWMB from pin D3 – Timer2 PWM2B

Current Sensor Jumpers: The Infineon BTN7960B power chips used in the MegaMoto

provide a current mirror output that reflects the current passing through the high side of the

half-bridge inside each chip. This current is passed through a 634 ohm resistor to provide a

voltage that can be read by the Arduino CPU. Since the low side of the half-bridge provides

no output on the current sensor pin it is possible to connect the sensor outputs from both

power chips in parallel. When the MegaMoto is configured as an H-bridge the current sense