Coil current ramp

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Coil current ramp

Postby brett nz » Fri Jun 28, 2013 9:35 am

Hi all, just been reading some of the case studies in library. Great reading.
https://www.picoauto.com/tutorials/friday-afternoon.html by Nick Hibberd. Looking at the coil current ramp and its characteristics. I have attached my first coil current ramp capture from a known good firing coil on a Nissan Primera. A little bit different from Nicks. Can anyone tell me anything about what im seeing here? We have max at 6.5A with a charge time of 4.3ms. The ramp itself seems to be slightly different with a few oscillations in the very beginning and when switch is closed drops to about 1V then slowly down to 0V? Any tips for me.

Thanks in advance.
Attachments
coil current ramp.JPG
coil current ramp.JPG (14.17 KiB) Viewed 1659 times
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Re: Coil current ramp

Postby Robski » Fri Jun 28, 2013 10:56 am

Brett,

As mentioned before it's hard for us Pico users to manipulte your captures as they are from a different scope/software.
In that same capture you could have included the primary & secondary to give the full picture of that one ignition event.

Different ignition systems will have different characteristics from marque to marque.
But from the one current capture you have posted i see there are the initial turn on oscillations & no steep up ramp showing no shorted coil, i cannot tell you anything about the 'turn off' time as there isn't any file posted & if there was i don't have your SW to open it. It doesn't appear to be a current limiting system neither from that screen shot, pretty much all i can give you from one picture like that :?
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Re: Coil current ramp

Postby Fat Freddy » Sat Jun 29, 2013 1:41 am

As Robski said.

Also Nick points that out in his study.
Needless to say, each captured trace should be very similar, having a good self-inductive ramp, a good peak current, and a clean release.


Its comparative.

The most important part is the peak current and "turn off". If thats OK you know the coil is being driven correctly therefore the fault is coil onwards.


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