Vex Robotics 276-2271 User manual

Power Expander • 1
accessories
Power Accessories
Limited 90-day Warranty
This product is warranted by VEX Robotics, Inc. against manufacturing defects in material and workmanship under normal use for ninety (90)
days from the date of purchase from authorized Innovation First dealers. For complete warranty details and exclusions, check with your dealer.
VEX Robotics, Inc.
1519 IH 30 W
Greenville, TX 75402
0412
Use the VEX Power Expander to add a secondary power source for four of the PWM outputs on the VEX
Microcontroller. Balance a robot’s motor load across two batteries to extend robot run time and increase
performance.
The “In” and “Out” ports are labeled “A, B, C, D”. Each “In” port is paired with an “Out” port. A motor or
servo connected to an “Out” port is controlled by the Microcontroller Motor Port connected to it’s corresponding
“In” port. (i.e. “In” port A controls “Out” port A)
Power Expander
STATUS
A B C D
OUT IN
“Out” Ports
Status Ports Feedback LED
“In” Ports PWM Lock
(slide)
For More Information, and additional Parts & Pieces refer to:
www.VEXrobotics.com
Power Expander
Usage
• Connect a secondary 7.2V battery to the power connector of the Power Expander. The Power Expander LED
should ash green briey signaling power is being supplied to it.
• Connect up to four (4) Microcontroller Motor Ports to the “In” ports of the Power Expander using 3-Wire
Extension Cables.
•Connect Continuous Rotation Motors or Servos to the corresponding “Out” ports of the Power Expander.
• Slide the Power Expander PWM Lock to secure cables.
• Turn on your Microcontroller. The feedback LED should now show the status of the Power Expander and motors/
servos should respond normally based on the secondary battery power.

Power Accessories
Power Expander • 2
accessories
LED Feedback
The Power Expander also incorporates an internal circuit breaker to prevent damage to the unit or connected
devices. Refer to the following LED status chart for more information. The Feedback LED provides the battery and
circuit breaker status of the unit.
Power Expander, continued
Power Expanders, no revision, Rev NC1, A or A1:
With PIC Microcontrollers, divide the analog port value by 70.8.
Example: The PIC analog value is 460. 460 / 70.8 = 6.5
6.5v is the current voltage of your Power Expander battery.
With Cortex Microcontrollers divide the analog port value by 45.6.
Example: The Cortex analog value is 297. 297 / 45.6 = 6.5
6.5v is the current voltage of your Power Expander battery.
(See errata)
Power Expanders of revision A2:
With PIC Microcontrollers, divide the analog port value by 155.
Example: The PIC analog value is 930. 930 / 155 = 6.0
6.0v is the current voltage of your Power Expander battery.
(See errata)
With Cortex Microcontrollers divide the analog port value by 70.
Example: The Cortex analog value is 455. 455 / 70 = 6.5
6.5v is the current voltage of your Power Expander battery.
Errata, Rev A and Rev A1 Power Expanders with Cortex:
Due to loading of the Cortex analog circuit, the Power Expander LED will blink red even though the
battery is good and the internal circuit breaker is not tripped. VEX Robotics can update Rev A and Rev
A1 Power Expanders to Rev A2. This will restore normal LED response.
Errata, Rev A2 Power Expanders with PIC:
NOTE: Analog values are valid over the range of 6.5v - 4.5v. Suggested threshold values are: above 974
is good (6.3v <= batt), between 851 - 973 is battery low (5.5v <= batt <= 6.3v) and below 851 is
battery critical (batt <= 5.5v)
If the value drops below 4.8v, the internal Circuit Breaker may have tripped.
Status Port
The Power Expander includes a Status port that can be connected to an Analog/Digital input on the VEX
Microcontroller. The VEX Microcontroller can use this data to calculate the approximate voltage of the battery
connected to the Power Expander. To determine this value, divide the Power Expander read-out as follows. The
examples are for a 10-bit result (maximum value of 1023). If using a compiler with 12-bit resolution (max value
of 4095), multiply the analog values and divisors by 4.
Green Battery Good
Yellow Battery Low
Red Battery Critical
Slow Red Blink Circuit breaker is tripped
Fast Green Blink Circuit breaker was tripped / Battery Good
Fast Yellow Blink Circuit breaker was tripped / Battery Low - Charge soon
Fast Red Blink Circuit breaker was tripped / Battery Critical - Charge Now