Peter,
Where is the schematic of the BMS system?
On the noise, I remember looking at two grounds, and seeing the noise spikes, so some of it is being transmitted via RF. Shielding the wires, and playing with some low pass filters, and/or RF chokes may help.
The source is the IMA, I remember turning off the breaker , and seeing it disappear.
Good luck.
The source is the IMA, I remember turning off the breaker , and seeing it disappear.
Done that and of course it works fine with IMA off
For info here are the Master & Digital slave circuit diagrams. There are 50 slaves (cells) with the Master bus outputs in parallel all connected to the Master Board master bus input.
Can you use input filtering by using a digital pulse filter that requires an input pulse of a specified length before it generates one. The spikes would all be eliminated if you adjusted the input to require a pulse of just short of the actual data pulse length. I am assuming of course that the data pulses are much longer than the spikes. This kind of filtering is much more effective than cap/res/ind filtering and much more effective that shielding. You could use a hex chip that could filter 6 lines all at once. It requires very little circuitry, maybe one or two chips and a few resistors to set the pulse width.
__________________
Jim Isbell
2000, 5 speed, 250,000 miles
"If you are not living on the edge, well then,
you are just taking up too much space."
Pulse width does NOT equal Frequency. Frequency is measured in cycles per time period and pulse width is measured in time period. The two could NEVER be equals. There IS a relationship however.
IF the pulse width is the width of a symmetrically repeating pulse, then it can be said that the pulses per time period is the frequency, but not the pulse width itself.
If the pulse width desired is longer than the pulse width of the noise, then you can build a digital filter that looks at the pulse width of the incoming pulse and if it is less than the desired pulse width it is NOT passed through. It has nothing to do with frequency...or at least very little to do with frequency. On the other hand a capacitor/resistor/inductive filter IS very much about frequency.
__________________
Jim Isbell
2000, 5 speed, 250,000 miles
"If you are not living on the edge, well then,
you are just taking up too much space."
However, given that the IMA output is analog then its noise will most likely be one of frequency and amplitude - "analog". And maybe characterizeable in pulse width terms sufficiently enough to filter by the method you suggest. R/C and filter choke noise filter systems are limited.
Just an "Old School" train of thought here... Indeed, your suggestion may be the clear winner.
The "data" is a square wave pulse. All the "analog" noise would be clipped by such a filter and become, essentially, a square wave, it is easily measured as pulse width and could be measured by a simple "one shot" that has an input width of a size just under equal to the data you are looking for. Any noise that lasted for less than the length of the desired data would not generate a pulse at the output of the One Shot. If a pulse of the length of the data came in, it would generate a pulse of equal length. Thus everything of shorter duration, whether sine wave, square wave, or random pulse, would be rejected and the buss would remain silent....until a pulse of the proper...or longer width arrived at the input. You could even get fancy and design it to reject pulses of LONGER length as well. Though in this case I suspect the noise is of narrow width.
The traditional R/C/L filter has a slope, so even though it removes some of the noise, there is a decibel range above which some of the noise comes through ANYWAY and the closer the pulse width is to the desired pulse there is also some feed through. A digital filter is absolute, nothing comes through if it isn't the width of the desired pulse, no residual noise, no mater how low.
What is nice about these filters is that they are 6 to a chip, already designed and all you do is add 6 resistors to set the pulse width and you have a filter that will handle 6 lines....and they are dirt cheap, pennies. Since there is already a digital board available then the power circuitry is already there. AND these chips are available as 5 volt, 12 volt, and maybe even 24 volt versions to match the digital power buss.
__________________
Jim Isbell
2000, 5 speed, 250,000 miles
"If you are not living on the edge, well then,
you are just taking up too much space."
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Re: Phev Insight
I'll try the extra layer of opto isolation first.
Indeed, your suggestion may be the clear winner. 
