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How To Do And Not Do EMS Power And Ground Wiring/PCB Design 
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DRAFT:

This could probably do with a different shorter title, but I need to write this up in detail as a golden standard for when I'm asked about how it should be done, and what is flawed about other systems, or indeed boards designed for FreeEMS in an ignorant way.

General principals: star connections, separate return paths for different current sources/sinks, be aware that no wire is zero ohm
Power connections: BRV sense, CPU power/analogue power, output to ext map/tps/etc, 12v rail spike catching, high side drivers, always on, on with key
Ground connections: Master reference, 0v rail spike catching, low side drivers (inj and/or ign), accessory

Relative and absolute wire sizing - ground much bigger than power, power big enough for current + big enough for physical vibration resistance
Skin effect and redundancy

External noisy devices: external ign and/or low z inj drivers, pwm heater control widebands, pwm fuel pump control

two more aspects that I've forgotten about since I started writing it.... ???

TBC

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Mon Mar 14, 2011 2:29 pm
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