Wiring a digital input switch

[Raheel Farouk]

Hi,
Can someone explain how to wire a digital input switch. To what pin should it go and should i ground it to 12V. I am trying to wire a switch to turn anti-lag on and off

[Merlin]

Just connect the digi input to the 0v line through your switch
And program the input overrun boost


John P

[Holmz]

...And should i ground it to 12V.
...

You either run 12V to the switch and back to the ECU.
Or
You run the 12V to the switch with an ~5K-ohm resistor before the switch and ECU and have the switch ground the 12V (2-mA).

[Scott@FP]

On a digital input you don't need a voltage source they already have a 4.7K 5v pullup on them. Just ground it to go below the switch threshold voltage, its like 3.5v going up and 1.0v going down.

[Raheel Farouk]

…Just ground it to go below the switch threshold voltage, its like 3.5v going up and 1.0v going down.

So if I ground it to the 0V aux that would be fine right?

[Scott@FP]

…Just ground it to go below the switch threshold voltage, its like 3.5v going up and 1.0v going down.

So if I ground it to the 0V aux that would be fine right?

Yes both the digital inputs 1-4 and the AT 1-6 already have a 5v pullup so just ground to 0v engine or aux with the switch and set up the parameters.

[Holmz]

…Just ground it to go below the switch threshold voltage, its like 3.5v going up and 1.0v going down.

So if I ground it to the 0V aux that would be fine right?

Yes both the digital inputs 1-4 and the AT 1-6 already have a 5v pullup so just ground to 0v engine or aux with the switch and set up the parameters.

Are you saying ground it anywhere?
Or running a wire back to the ECU to ground it there?

I thought the advantage of the pull-up was one small wire to the switch, and not 2 ??

[Scott@FP]

In theory chassis ground would work fine, but reading the fine print on the digital inputs the negative swing switching threshold is 1v, to insure it functions always might be better to ground to aux or engine 0v. In the case of an AT you can set the switching voltage in software to insure a chassis ground issue won't happen, like 3v with a 1v hysteresis. My personal preference is to keep digitals away from any high current ground path, but there are 34 ways to skin a cat as they say.

[Holmz]

I agree with the idea of a twisted pair.
But the input should be low pass filtered?
And then again adding noise into the system can be mitigated with a twisted pair.

It probably helps to have a scope!

[Raheel Farouk]

Hi

I am trying to wire a switch to turn launch control on/off. But when I go into the digital input function selection there is no option for launch control. But there is an option for traction control. I don't have traction control setup. I only want launch control. Will selecting the traction control function turn on lauch control on/off? Any help will be appreciated.

Thanks,