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Practical Wiring - Professional Motorsport: Grounding Design

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Grounding Design


00:00 - When we're designing the power grounding scheme of our motorsport wiring harness, the same design objectives outlined in the wiring fundamentals course still apply.
00:09 And we achieve them in the same way by star point earthing.
00:13 The use of composite materials in the motorsport world is a factor we need to consider as the electrical conductivity of composite materials cannot be relied upon in the same way as a metal bodied vehicle.
00:25 Fibre glass is actually a very good insulator and although carbon fibre is usually conductive, I have seen mixed results when it's used as a conductor.
00:34 For this reason, when constructing a wiring harness for a composite bodied motorsport vehicle, I avoid using the body or chassis of the vehicle for any ground purposes.
00:44 And instead run all power grounds back to one single star earthing point.
00:49 This star earthing point is often the engine block but depending on the layout of the vehicle and wiring harness, can also be the battery negative post.
00:57 The choice between these two options is determined by examining which of them will result in the shortest overall power ground wire runs.
01:05 As this will reduce both the complexity and weight of our wiring harness.
01:10 An example of using the battery negative post as our star earthing point, is often seen on a single seat race car which uses a carbon fibre tub as the main chassis element.
01:20 Commonly the main elements of the electronics package will actually be fitted beneath the driver's seat or to one side on the tub and protected by a screen which doubles as a radiator duct.
01:32 In both these cases, the battery is usually mounted close the rest of the electronics package and grounding to the battery negative post is the optimal choice.
01:41 If this is the case, care needs to be taken to ensure that none of the sensors mounted to the engine ground through their body to the engine block as this will violate our star point earthing requirements.
01:53 And the readings from these sensors are likely to be offset or innacurate.
01:57 Sensors used in the professional motorsport world almost universally have separate ground pins which are isolated from their body so this is not a situation we're likely to strike often but it does need to be confirmed.
02:10 As with the power supply design, the sizing of our ground wires needs to be appropriate for their expected current load.
02:17 And we often run multiple smaller gauge wires in the place of a single larger gauge wire to make a crimp connection to a connector pin possible.
02:25 A specific example of this can be seen on most automotive ECUs.
02:29 As ECUs operate primarily as low side switches to control their connected actuators, they can need to pass a substantial amount of current to ground at times.
02:39 Almost all ECUs on the market will have more than one power grounding pin.
02:43 The reason for this being that a single pin could not handle the maximum expected current load.

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