Power

Power Boards
On the 2011 system, there is a board which has the regulator, fuses, and connectors for all of the power, and the turn-off switch.

This board is the most frequent to fail, as it is constantly having things plugged in and removed.

Time
To design and build the power board took 10 people hours.

Batteries
We have 7.2V NiMH batteries (1500mAh, 1800mAh, 3600mAh). They all charge at the 4A setting on our battery quick-charger.

We also have 3 7.4V 5400mAh LiPo batteries. They have a maximum charge rate of 5.4A and must be charged on the LiPo charge setting or run the risk of fire and explosion.

Chargers
We have an old battery quick-charger.

We have decided to get the Intelligent Battery Manager 606-D by G.T.Power Re. The digital battery charger can charge NiMH as well as a number of types of lithium batteries. It will run off of AC or DC power. The charge rate can be set between 0.1 and 6A. Care must be taken to charge batteries on the correct setting. If unsure about how to operate the charger cunsult the manual. Improper charging could destroy batteries or cause fire.

Sizing
http://www.joliebrisemodels.co.uk/tenth/rc.html See this page; batteries must be sized for both maximum and average discharge current.

Regulators
Regulators change the voltage level. Presently we use 1A linear regulators (LM7805), with 2 filter capacitors, and a 1A fuse on each regulator circuit.

Regulates the voltages so that components aren't fried by too high or too low a voltage.

7805 - 5V {C}7812 - 12V (dont think we need this?) {C}7833 - 3.3V

Data-sheet here: (insert link)

These are all 1A regulators.

http://knol.google.com/k/electronic-circuits-design-for-beginners-chapter-4# good basic reference about selecting voltage regulators

Heatsinks
We need to heatsink our regulators, depending on how much power they are dissipating and their thermal resistance (see the LM7805 data sheets). This is important, and needs to be done before the boat is water-tested.

Google "heatsink selection", there's some good info.

Wiring and Fuses
Wire, connectors, and fuses must be sized to current.

Fuses must be sized to protect wiring, batteries, and circuitry. Fuses we use are fast-blow.

In the past we've used Dean's Ultra connectors, rated to 10A or something high, for our batteries, theres a guide to soldering them here http://www.ezonemag.com/~awilletts/deansultra.mpg and it's also on dropbox.

Power Systems on GaelForce
Arduino can supply 40mA maximum.

Questions marks mean that I made it up quickly, and someone needs to actually look up the numbers.


 * Arduino 5V (200 mA)
 * RC Receiver 5V (200 mA?)
 * Compass 5V (50mA,15 in sample mode)
 * Pololo 5V (500mA?) and 12V (50mA?)
 * Multiplexer 5V (10mA?)
 * RS232 to TTL 5V (1mA)
 * Wind sensor 12V 150mA?); 1A fast-blow fuse required
 * Smartwinch 3.8->9V (18A stall current)
 * Rudder servo 5V (4A stall current?)

Power Systems on GaelForce II
As of June 2011, the current power system for GaelForce II is as follows: Total curernt draw : 415mA for sensors/ electronics, between 100mA idle, around 1.5A no load on motors
 * Arduino 5V (200 mA)
 * Compass 5V (50mA,15 in sample mode)
 * Pololo 5V (500mA?) and 12V (50mA?), 5V is currently unused and draws no power.
 * RS232 to TTL 5V (1mA)
 * Wind sensor 12V (150mA?); 1A fast-blow fuse required
 * Smartwinch 3.8->9V (18A stall current, 23mA idle, 650mA no load current)
 * Jib Servo 4.8 -5V(1800mA stall current, 285mA at no load)
 * Rudder servo 4.8 -6V (180mA at no load)

8A with all motors at max.

Research for 4m Power
http://en.wikipedia.org/wiki/Battery_management_system

This stuff is complicated: http://www.mpoweruk.com/bms.htm we ideally want something off the shelf? this seems like way too much detail.

Will design systems for $$: http://www.claytonpower.com/power/renewable/

"designing battery management systems": http://www.edn.com/article/512154-Designing_battery_management_systems.php

Monitoring
Power monitoring to detect low voltage is important

There's a chip we have on hand to shut down things at certain voltages (MAX696EPE+-ND)