RC08Power

The 2008 power supply circuit uses the same switching topology as the 2007 system with some changes, most notably a jump in system voltage to 12V from 9V to support the new motors. Another change is more analysis in the design phase including looking at possible interference with the radio and other devices that use oscillators.

Tasks

• [X] Finalize specs on voltages, maximum current draw, and allowable frequencies
• [X] Select a part based on the spec
• [X] Determine how to mount batteries
• [X] CAD the design
• [X] Verify the design
• [X] Fabricate Prototype

Specifications

Power Supply

• 12V operation
• Small package
• Low inductance
• High allowable RL (so we can use smaller inductors)
• Frequency does not interfere with other electronics
• Protection Circuitry (TVS:Transient Voltage Suppression)

Specification

Part	VBatt	5V	3.3V	2.5V	1.8V	1.2V
FPGA			1 mA + 12*n mA n pins high	8 mA typ 12 mA max		8 mA typ 27 mA max
ARM			15 mA max		15 mA max
HP3 RX
HP3 TX
FET Drivers (each)	9mA
FET Drivers (total)	45mA
Maxon Halls	??
Micro Mo Halls		??
Kicker Board	4A (when charging)

The FPGA has between a 2.5K and a 10K pullup, and between a 4K and 34.5K pulldown. Thus, the bus pins (D0-D7) are expected to draw max ~1 mA when driven into the FPGA.

Parts and Supplies

• 3V3 @ 3 A supplies all linear regulators
• 2V5
• 1V8
• 1V2

Battery

• Packs need to be configured to give out 12V
• Orientation and number need to be spec'd by both EE and ME
• Possible on-board charger? maybe in 2009
• Battery health monitor
• Affordable

Similar to last year, we will probably go with NiMh batteries because we cannot afford Li*.

Quick notes on available batteries

Tenergy Batteries have done well (enough) in tests, and the internet seems to think they are ok.

• 2600 mAh AAs $24 free shipping and a travel charger
• 2300 mAh AAs $26 with solder tabs

Supposedly these coupons "tenergy2547" and "septspecials" can save us 10% from this slickdeals post.

Schematics

• 

  Power Supply Schematic

Links

• Electrical System