One idea you might want to look into is to measure the VCEsat This should 
give you a good indication on how much current is flowing. assuming you use 
a pic for timing you can determine what would be close to the optimum time 
to start current to the coil for the next spark.

Peter

----- Original Message ----- 
From: "Sascha" <sascha@go.ro>
To: "'Microcontroller discussion list - Public.'" <piclist@mit.edu>
Sent: Wednesday, November 03, 2004 1:08 AM
Subject: RE: [EE]:Coil core saturation


> Hi guys,
>
> I am designing a multispark ignition for my car and I encountered a 
> problem.
> I whant to know how much time the ignition coil needs to be driven so it
> stores the maximum magnetic field in it's core. Unfortunately I can not 
> find
> the specs of the induction coil so I can compute it. Is there any way I 
> can
> find this time? The induction coil has a primary winding of about 200 
> turns
> and a secondary winding of 20.000 turns. That's all I could find about it.
> If I keep the driving transistor saturated too much I loose power and if I
> turn it off too soon I will loose energy in the spark. None of this is
> acceptable.
> First I thought of adding a emitter resistor and measure the voltage drop
> across it. But this again means power loss 1.5V across the transistor, 0.5
> across the resistor and if the battery is not very strong when I try to
> start the car it will drop to 9-10V so the remaining voltage across the
> induction coil will be as low as 7V. And this will translate as a weak 
> spark
> right at the moment where I need the strongest.
> I want to drive the coil with a BUT12 transistor which is driven by a PNP 
> or
> a PMOS.
>
> Any suggestions?
>
> TIA,
> Sascha
>
>
>
> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf 
> Of
> Roland
> Sent: Tuesday, November 02, 2004 10:16 PM
> To: Microcontroller discussion list - Public.
> Subject: Re: [PIC]:PIC's and CAN
>
> At 08:41 AM 02/11/2004 -0800, you wrote:
>>I have decided that I want to learn about networking PIC's ( 18F258 or
>>18F458 depending my total IO needs) via a Computer Area Network (CAN).
>>I looked at the Microchip site and the app notes, but they are not meant
>>as introductory material.  A 'GOOGLE' search did not turn up anything
>>either.
>>
>>Does anyone know of a tutorial or introduction to CAN?  With a PIC would
>>be a bonus.  :)
>
> Hi
> Not explicitly tutorials, but I found these to contain reasonable intro
> material. Unfortunately did not record all the URLs.
>
>
> http://ams.cern.ch/AMS/Dataformats/node2.html
>
>
> AN247 A CAN Bootloader for PIC18F CAN Microcontrollers
>
>
> APPLICATION NOTE (Philips)
> Determination of Bit Timing Parameters for the
> CAN Controller SJA 1000
> AN97046
>
>
> Parallel or Serial CAN Connection Using External CAN
> Standalone CAN Controllers with the Motorola
> M68HC908 Embedded FLASH Microcontrollers
> Designer Reference Manual
>
>
> For a full technical introduction to Controller Area Networking, see
> http://www.hitex.co.uk/can
> The full Softing CAN Products Catalogue can be found
> here(http://www.hitex.co.uk/softing/IC_CA_01E.pdf) (1.9MB PDF)
>
>
> Regards
> Roland Jollivet
>
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