12volt to 5volt for Ecu Aux
Turbo Mini Forums

Can anybody tell me how to reduce a 12-14v volt down to a 0-5 volt signal to my Dta Ecu. When I activate nitrous in want the ecu to retard ignition.

Class C 3rd Place Avon 2011 14.18 @101mph

I'm not familiar with DTA but it must have a 5V out for all it's sensors.

If so, the simplest (but crude) way would be to use a small relay with a 12V coil to switch the ECU's own 5V back to the input line that you want to activate.

I assume this is just an on/off 5V signal you want ???

Schrödinger's cat - so which one am I ???

Yes, just want a 5v on/off. The Dta does have 5v out. I was originally thinking using the circuit from a 5v in car mobile charger.

Edited by alaskanow0 on 19th Aug, 2012.

Class C 3rd Place Avon 2011 14.18 @101mph

Use the DTA's own 5V, not an external one - it's own one will be ground referenced within the ECU box.

External 5V sources won't be the same actual 5V (VCC or VRef) nor the same ground plane, so could compromise the ECU chip.

There are better ways than a relay but it depends if you want to start soldering transistors and the such like.

But a relay switching the ECU's own 5V is the simplest solution.

Schrödinger's cat - so which one am I ???

Thanks Rod, relay it is.

Class C 3rd Place Avon 2011 14.18 @101mph

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

The way I controlled the nitrous was using a the ECU settings. The nitrous controller in the ECU is 'activated' by a toggle switch on the dash which simply grounds one of the digital inputs to the sensor ground. Most ECU digital inputs are 5v pull up internally so that when grounded it pulls the 5v to ground, thus it is either on or off. Above 90% TPS the ECU grounds the output that is connected to the progressive nitrous controller's activation input (normally the micro switch on the throttle)


Doing it this way means that the ECU replaces the throttle micro switch, with the added advantage of retarding the ignition advance and trimming the fuel. The fuel trim is usesful only to trim the jetting that is already fitted, rather than privide the extra fuel and eliminating the fuel jetting altogether. Some ECU's will also disable the nitrous when it detects an AFR or lambda outside of the safe range, which is advenatgous.

As has already been mentioned, do not even consider using an external 5v supply as this could push negative volts through the chip and damage it. Use only the ECU's own 5v and sensor grounds to avoid damage, depending on how well the ECU's inputs are protected in the first instance.

Edited by Sprocket on 19th Aug, 2012.

That was the plan, but wasn't sure how to activate aux only when nitrous was in use.

Class C 3rd Place Avon 2011 14.18 @101mph

Matt this doesn't suprise me one bit, lol

Audi s4 b5 - 470bhp & 486ft lbs

On 30th Apr, 2012 Brett said:
yeah stick the bit in and give it a wobble

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will