sharing input signals

Discussion and support for MoTeC's previous generation ECUs.

sharing input signals

Postby sphilips on Thu Feb 28, 2013 8:06 am

I have a m800 and aim mxl which are sharing (though wire splice) a front suspension signal. On both the aim and the m800 I have a bit of noise. I don't have this noise on the mxl when I don't connect the wire to the m800.

The mxl give current to the suspenion sensor.
The sensor output is connected to the av6 input.

Maybe a a resistor? Or a diode? or connect to the at inputs?

Thanks
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Re: sharing input signals

Postby stevieturbo on Fri Mar 01, 2013 12:19 am

A lot will depend on wiring, wiring routing, grounding and sensor type.

ie, is this a rotational/pulsed sensor, resistance, voltage based ?

Is any wiring routed near any sources of interference ? Does it require any shielding ?
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Re: sharing input signals

Postby sphilips on Fri Mar 01, 2013 1:20 am

the sensor provides a 0-5v output.
the m800 and mxl share the same ground. they are connected through the can bus system.
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Re: sharing input signals

Postby Holmz on Sat Mar 02, 2013 9:24 am

It Is almost certainly a ground loop problem so shielding will not likely help.
You may want to run the wires with a fat ground around them and try tying that to the AIM, the M800 or both. Or some different path to minimize loops.
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Re: sharing input signals

Postby mstech on Sat Mar 02, 2013 7:04 pm

I have an oil temp sensor shared between a EVO4 and a M84, the sensor output is shared through a splice, but the 5V and GND are handled by the M84, there is a CAN connection between them as well. I do not have any more noise on this setup than with a straight connection into either a M84 or EVO4.
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Re: sharing input signals

Postby Holmz on Sun Mar 03, 2013 11:46 pm

mstech wrote:I have an oil temp sensor shared between a EVO4 and a M84, the sensor output is shared through a splice, but the 5V and GND are handled by the M84, there is a CAN connection between them as well. I do not have any more noise on this setup than with a straight connection into either a M84 or EVO4.


Do you have the 5V and ground running along with the sensor output?,
and also do you have the spliced wire running alongside another ground wire to the other unit?

I am sure if you tried you could probably find a way to get noise onto it.
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Re: sharing input signals

Postby Scott@FP on Thu Mar 07, 2013 4:06 am

Mx00 has a 100K pulldown on the AV, maybe the AIM unit does not?
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Re: sharing input signals

Postby Holmz on Thu Mar 07, 2013 7:21 am

Scott@FP wrote:Mx00 has a 100K pulldown on the AV, maybe the AIM unit does not?


The 100k pull down will affect the mean (DC) level of the signal more than the (AC) noise level.
Noise can be voltage (RF) induced or magnetic field induced.

I once spent hours on a 50Hz hum in a stereo (only on the turn table), before I figured out it was the wiring of the lights in the ceiling that made a coil and magnetic field that the turntable was picking up.
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