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 Post subject: Launch Switch
PostPosted: Tue Apr 24, 2018 10:03 am 
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Joined: Tue Sep 13, 2016 9:06 am
Posts: 59
ECU Model: S80 Pro
I'm trying to figure out a grounding strategy for my ECU, Dash and Buttons.

Looking at the S80 wiring diagram PDF, I see that the launch control button should be a switched input using a signal ground.

I have a 12 conductor curly cable, and 10 buttons on my wheel. Leaving two conductors for grounds. One ground was going to be used for 12v switching (Relays), the other ground would be for 5v switching (dash and ecu).

Does it matter? Should I try and get hold of a 13 conductor cord instead?

Thanks


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 Post subject: Re: Launch Switch
PostPosted: Tue Apr 24, 2018 10:11 am 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2852
Location: Norn Iron
ECU Model: No ECU
Explain exactly what you're intending to with said switches and wiring ?

Launch etc just needs a ground...it doesnt really care where this ground comes from.

When you talk of 5v, that suggests sensors, which must always reference to sensor ground.


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 Post subject: Re: Launch Switch
PostPosted: Tue Apr 24, 2018 10:35 am 
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Joined: Tue Sep 13, 2016 9:06 am
Posts: 59
ECU Model: S80 Pro
Some inputs for my dashboard, and a switch for launch which goes to the ECU, that's it. The other buttons and switches on the wheel are negative triggers for 12v relays which power things like wipers, lights, starter, etc.

No sensors, perhaps I'm getting my terms mixed up a little bit. My dashboard, and the dta ecu work on similar logic levels which is why (wrongly or rightly) I thought I'd have anything that is 5v (dash, ecu) on one shared ground. Then anything 12v on another.

Sounds like that doesn't really make much difference if we aren't talking about sensor grounds, which is good news. I can get on with wiring up my steering wheel now.


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 Post subject: Re: Launch Switch
PostPosted: Tue Apr 24, 2018 10:51 am 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2852
Location: Norn Iron
ECU Model: No ECU
Any of those simple switched inputs to the ecu, like TCS, ALS, MAP2, Launch etc will be happy with a ground, whether sensor ground or normal ground. But do not interconnect the sensor ground with vehicle ground anywhere.

But if you can keep things like those switches referenced to ecu sensor ground...it keeps all ecu things, dedicated to the ecu so no risk of external influences.


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 Post subject: Re: Launch Switch
PostPosted: Tue Apr 24, 2018 11:33 am 
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Joined: Tue Sep 13, 2016 9:06 am
Posts: 59
ECU Model: S80 Pro
Thanks!


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 Post subject: Re: Launch Switch
PostPosted: Tue Apr 24, 2018 2:43 pm 
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Joined: Fri Feb 28, 2014 1:03 pm
Posts: 1030
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79
I kept mine separate.

ECU switches (launch, etc.) use ECU sensor ground.
Dash switches (paging, etc) use dash sensor ground.
I don't have power grounds like you, but they would go to a separate power ground.

It's too easy to introduce ground loops. Belt and braces for me.


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 Post subject: Re: Launch Switch
PostPosted: Wed Apr 25, 2018 4:25 am 
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Joined: Tue Sep 13, 2016 9:06 am
Posts: 59
ECU Model: S80 Pro
In a perfect world I'd do that, but my curly cable is short of conductors! :(

The 8STA connector I have has 13 as well. I've dropped request in with the supplier of curly cables to see if they do anything with 13 or more.

I think for the time being I'll wire it up with 12, then if there are any undesirable effects I'll certainly look to spend the money on a replacement curly.

Thanks for your input.


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 Post subject: Re: Launch Switch
PostPosted: Wed Apr 25, 2018 6:17 am 
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Joined: Tue Jan 16, 2018 9:38 am
Posts: 31
Location: Aberdeen
ECU Model: S100 Pro
Distributor: DTA
Tim,
Demon tweeks sell a 12 way curly cable with a screen; I used the screen to enable all 13 pins of the 8STA to be used on my steering wheel.
For info, I did keep signal ground (for the switches and pots) and normal ground (for the power for the dash) separate, but would have joined them up if short of conductors.
Steve


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 Post subject: Re: Launch Switch
PostPosted: Wed Apr 25, 2018 8:18 am 
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Joined: Tue Sep 13, 2016 9:06 am
Posts: 59
ECU Model: S80 Pro
The cable I have is screened as well, and I'd have never thought to use it in that manner.

Learning something new every day with this stuff, thanks for your input!


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 Post subject: Re: Launch Switch
PostPosted: Wed Apr 25, 2018 9:32 am 
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Joined: Tue Sep 13, 2016 9:06 am
Posts: 59
ECU Model: S80 Pro
Ordered a DCE coiled cable from Tweeks this afternoon, the coiled cable I have is slightly too short. They're also much cheaper than my original option when you factor in costs of delivery.


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