Grounding issues are very common in this type of electrical environment.
A first step is make sure that units involved are "star grounded". That is each unit involved should have a separate ground wire preferably to the - terminal of the battery.
Also decoupling of supply voltage noise is crucial. Every unit should have a a low esr capacitor across its supply lines located as close to the unit as possible.
These are only general guidelines since you do not provide any details
It'd be worthwhile knowing what kind of car this is (modern car or older/classic) as well. Older cars don't have the protected electrical system that modern cars have.
nilton61:
Grounding issues are very common in this type of electrical environment.
A first step is make sure that units involved are "star grounded". That is each unit involved should have a separate ground wire preferably to the - terminal of the battery.
Also decoupling of supply voltage noise is crucial. Every unit should have a a low esr capacitor across its supply lines located as close to the unit as possible.
These are only general guidelines since you do not provide any details
hi there
thanks for the info.
This was going to be my next step, giving a GND to each sensor in the engine bay. Taking it all the way to the - on the battery isnt going to happen though due to its boot location plus the chassis is GND, so that will be fine. Plus it would build a resistance at that distance.
I am a newbie to techy stuf, so please forgive me, but "esr capacitor".... whats one of those and you say across its supply lines? As in sensor power supply?
I have a RPM sensor, MAP sensor and TPS sensor. All share a common GND and a common 5v supply...but a independent one from the power reg board I built.
thanks again.
and I changed the alternator today due to it faulting this week...hoped it may have been the noise issue...wasnt so lucky!
its a 1998 diesel engine. 2000 engine loom. Mechanical diesel injection. Very little electronics going on.
If the sensors are all in the engine bay, then I suggest you ground to the Arduino and its voltage regulator to the car ground in the engine bay near the sensors, and nowhere else.
Put some filtering on the all the Arduino inputs, such as a 47K resistor in series with each Arduino input pin, and a 0.1uF capacitor between each input pin and Arduino ground.
Piggy1987:
This was going to be my next step, giving a GND to each sensor in the engine bay. Taking it all the way to the - on the battery isnt going to happen though due to its boot location plus the chassis is GND, so that will be fine. Plus it would build a resistance at that distance.
I am a newbie to techy stuf, so please forgive me, but "esr capacitor".... whats one of those and you say across its supply lines? As in sensor power supply?
I have a almost perfect continuity...but I get interference/noise on the line.
There is some need for clarification here. First of all, there is no such thing as perfect continuity unless we talking superconductors. All other materials have some resistance. And low resistances are hard to measure, below 5 ohms you will have to use special instruments or special methods to get reliable readings. This also means that all materials that carry some current will exhibit a voltage drop that is proportional to the resistance and the current.
Since cars have low voltage systems the currents can be substantial tens of Amperes are quite common. Also iron is a poor conductor compared to copper and its prone to corrosion. In a car the chassis is normally used as the return conductor, this means that all currents from all electrical apparatus return to the - terminal through the chassis. These currents can easily add up to 100A. So even if the resistance in the chassis was 10mOhm this would result in a voltage drop of 1V. This voltage drop would in turn affect all electrical apparatus. One good example of this are old cars where the resistance in the tail lights has increased so much due to corrosion that the lights start to blink when you turn on the turn indicators.
All this is true for both dc, low frequency and high frequency currents with the problems worsening the higher the frequency gets. This is the reason for the star grounding i mentioned. A complete star grounding may be impractical because of the amount of wiring needed. But what you can do is connecting the ground from all your sensors and the arduino together to a single ground point. This single ground point should in turn be connected with the - terminal on the battery with its own wire. That way you ensure that no voltage drops from other sources are interfering.
ESR stands for Equivalent Series Resistance in capacitors. The lower the esr the better the capacitors ability to absorb interference. These capacitors should be connected at a as close distance as possible to the power supply terminals of each unit. The value will depend on the current consumption of that unit
