[Diy_efi] New MegaWideband schematic

[Jorgen Karlsson]

Perry Harrington wrote:

> Jorgen Karlsson wrote:
> > I took a look at the schematic and I can't find any current regulation
> > (other then R12, but that will not regulate current very well)
> or current
> > sensing for the Ip current. I can't see how it will work without it.
>
> It's all done using PWM.  It uses the same principal as the
> MegaSquirt and Bernd's
> DDL.  The current is 'known' for the Ip as a percentage of max
> (6.1ma).

I do not agree, we would need to assume that the pump cell impendance can be
calculated from the known heater temperature. We will also need to assume
that the ramp up and ramp down of the IP current are well defined over the
temperature and impendance range of the sensor. Even if we make the above
assumtions we will probably be close but I would feel better if we knew the
temperature of the nearst cell and if the current was regulated.

> For
> the heater, we know the heater's impedance at various
> temperatures, and thus
> can regulate current.

Regulating the heater temperature is not a big problem. But can we assume
that the pump and sense cell is at the same temperature as the heater?

> Mail away, the more info out there, the better.  I think it's
> also important
> that as much prior art on these things is released so that
> companies don't patent
> the most accessible ways for DIY folks to do stuff.

Good point.
I did some changes to the circuit yesterday, nothing that change the
operation but I replaced two IC's with a few discrete components. I will
send it as soon as I have checked it once more. That will probably be
tomorrow as it is a few minutes after midnight here now.

Jorgen



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