MC3334 dwell control

[Stuart Baly]

Gday,
	I came to the same conclusion while looking at the High 
Energy ignition kit published in Silicon Chip a few years back, but 
for a different reason. If you have a look at the Silicon Chip kit 
design and the DDIS design, there's no sense resistor, so neither 
of these designs can measure coil current, so no dwell control.

My opinion on this is that it'd be better from a parts count and 
configurability viewpoint to control the dwell using the 
microcontroller. Maybe even measure the coil current in real time 
using a sense resistor and one of the 8535's ADC inputs if you're 
clever.

Stuart.

On 7 Mar 2002, at 1:00, MWP wrote:

> Date: Wed, 6 Mar 2002 02:15:05 +1100 (EST)
> From: MWP <mwp at overclockers.com.au>
> Subject: MC3334 dwell control.
> 
> Hi all...
> 
> My first post to diy_efi so please be patient with me :)
> 
> Ive read all the info i can find on using the MC3334, but it seems to me
> a
> lot of people are using it incorrectly.
> 
> It seems many people are using this schematic as a base:
> http://www.diy-efi.org/diy_efi/projects/ddis/ignitor.gif
> ... with the IN- grounded at the controlling circuitry.
> 
> >From the data sheet for thr MC3334 it seems as if gounding this output and
> sending a digital signal to the IN+ completely removes the dwell
> controlling section of the IC.
> 
> Has anyone found an effective way to fix this for use with a
> microcontroller?
> 
> I was thinking of using a 3k:3kohm coupling transformer between the
> microcontroller and the MC3334. This way the IN- should still work
> correctly.
> 
> Anyone have any opinions on this?
> 
> Thanks,
>  MWP
>Building a 4cly twin-coil wasted spark system using MC3334's 
>and a Atmel
>AVR At90S8535 MCU. Programmable vis RS232 from a PC.

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