Whats the Pefered Method to Wire for Voltage Dist? 2

[MICR0]

I have a new ECU that I'm wiring to an engine with a significant number of sensors. Each 3 wire) sensor needs to be supplied with a 5v signal from the ECU. Since I cant wire them all individually in to the one output pin of the ECU, what would be the simplest method for connecting them all? I'm hesitant to run a wire all the way to each sensor and tie the in to common block fed by the ECU as that doesn't seem too elegant. I guess I could piggy back with the lead going to one sensor then another and so on and so forth. Is there a common practice?

thanks

 

[dicer]

All sensors have individual inputs to the ECU. If you don't connect them all individually how does the ECU know which one is which?
Don't you have install instructions for this new ECU? If it's an aftermarket unit it should have very well detailed instructions.

 

[patprimmer]

I think (maybe) he means that each sensor needs a 5 volt input, but they put out a signal on another wire that the various ECU connectors read

Regards
Pat
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[WGJ]

Power connections to sensors need to be wired in such a way that volt drops are minimised.
A decent, low resistance connection to each sensor will ensure long-term reliability and robust engine operation.
One of the issues sometimes seen on systems where the OEM has skimped on the vehicle wiring is the gradual increase in connector contact resistances, added to scrawny wiring resistance, giving the 5V regulator in the ECM drop-outs during cranking, which may then corrupt signals from sensors that contain electronics/ASICs which may depend on the 5V regulated supply for plausible outputs. Things like Hall effect cam and crank sensors, for example. Corruption of these signals will probably prevent a start.

Bill

 

[MICR0]

FWIW this is a complete prototype application so there is no existing harness and I'm building one from scratch (fun). I've decided to distribute power, and likewise provide a reference ground, by wiring everything to a terminal block wired just off the ecu. This should make the wires to each sensor roughly the same length and therefore keep impedances as equal as possible. Is there anything obvious that I'm missing?

 

[WGJ]

Don't try and sneak any other loads into the sensor power supply. Any unnecessary loading could try and pull a 5v ECU regulator to the point where regulation or even all voltage is lost.

Bill

 

[jbkettler]

First - to answer your question directly - the most elegant is going to be to start with a single connection at the ECU and install a splice pack with a lead going to each sensor from that. Put the splice in a central location to the sensors it feeds. This splice can then be properly sealed to minimize degradation of the connection. A terminal block typically referes to an open to atmosphere connection point with screwed connections - good for quick and dirty (i.e. a quick hookup to make sure everything works before final fabrication of a wire harness - maybe what you should do with the prototype), not so great for long term and open to environment.

In addition - The 5V output from the ECU should have a maximum rating (probably reported as maximum amps). Do not exceed this. Each of your sensors will consume some amount of power. You can power multiple sensors as long as their current consumption does not exceed the rated output of the 5V channel (Most 3 wire sensors consume very little power - but also most 5V references are only good to about 1 amp - on stock OEM ECU's). If the ECU has multiple 5V references, divide the sensors up logically between them.

 

[zzzjim]

A few of my thoughts (Re worked a harness for OFF ROAD)
a) Consider signals present , if any of the sensors produce small signals , screening and routing these away from High Current wiring produces a more tollerant design.
The above may not be true with modern sensors .
b) Unexpected grounds may produce ground loops and strange DC
offsets when starter engaged !

Some sensors are less important than others , a full undersatnding ot the function of each sensor may help in chosing its importance .