Grounding Scheme

[Healey3000]

Hi,

This is my first engine ECU attempt but I've done several mixed-signal layouts from which to draw on. I'd like your opinion on optimal grounding:

I typically run three separate grounds that are all tied together at one point (single point, star ground approach). These would be Power, Digital and Analog grounds.

The single point connection will be MS3's only ground contact point with the outside world, that is, it will go right to the engine block/head. All I/O, low-current lines will connect to Digital ground. This includes crank and cam Hall sensors, logic ignition coils, and things like switches. All analog sensors, both of the three-pin and two-pin variety will connect with Analog ground (TPS, IAT, etc.). High current returns, such as ignition coils, injectors, IAC will go to Power ground.

The question is how best to ground the shields on those cables that require shielded wiring. For example, a Hall crank sensor would be referenced to Digital ground, but should the shield go to Power ground? Normal mixed-signal practice would say that all noise sources should be drained off to stay away from signal grounds; in this case Digital and Analog.

Thoughts?

[jsmcortina]

This is covered in the wiring section of the Hardware manual. Have you had a look at that?

James

[Healey3000]

This is covered in the wiring section of the Hardware manual. Have you had a look at that?

James

Hi James,

Yes, I have read it and it was pretty helpful. The difference is that I am considering separate analog and digital grounds which offers the option of grounding the shields differently. Not sure if that provides any advantage or not.

Thanks.

[arran]

All grounds are connected together in the MS3. The grounding scheme (for reference is http://msextra.com/doc/general/grounding.html) has a signal ground which is just one of those ground wires that is separated out and the user wires the car such that it is not sharing ground current with high current returns. So if you want to then further separate digital from analogue grounds, just pick another ground wire and use that for all the digital signals returns.

I am not sure that is necessary in my opinion