[Diy_efi] DIY WB heater driver

[bcroe at juno.com]

That should work, if you can solve the calibration problem 
that each sensor may have a somewhat different heater.  
You will need A to D inputs for measuring the voltage and 
current.  

But then you need to ask how much benefit you can claim 
for this complexity.  Maybe a hot turbo needs it.

Bruce Roe

On Fri, 21 Jun 2002 20:03:09 -0700 Brian Dessent <brian at dessent.net>
writes:
> bcroe at juno.com wrote:
> > 
> > The heater tends to draw less current as it gets hotter,
> > partially compensating.  However this effect is not 100%,
> > since the heater actually needs to BE hotter to decrease
> > current.  A fancy system might actually measure resistance
> > (applied voltage divided by current flowing) and continuously
> > adjust power for the resistance representing the correct
> > temperature.  Part of the problem is that not every sensor
> > has the same resistance.
> 
> Well the idea is to maintain a given set temperature, no?  What if 
> the
> wb controller measured the cold resistance and the hot resistance of
> the  heating element, and do regulation based on this (the
> differential)?  Is the heater a wound nichrome wire or a ceramic 
> block
> (or something else)?  Its resistance should have a pretty linear
> tempco.  This would probably require a microprocessor, but it might 
> have
> the benefit of having a crude EGT estimate output.
> 
> Brian
> 
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