[Diy_efi] Use O2 sensor on motorcycle?

[bcroe at juno.com]

An SCR is great for charging a battery from the AC line 
(esp if you use a fero-resonant transformer).  With a 
1 amp load, power dissipated wouldn't be much over a 
watt.  BUT an SCR once triggered will only turn off when 
the power is (briefly) removed.  Thats great for AC power 
that stops and reverses 120 times a second.  But not at 
all practical in controlling DC power.  Even the rectified 
DC from a vehicle alternator is generally 3 phase, which 
means it never drops all the way to zero.

Bruce Roe

On Tue, 04 Jun 2002 23:47:11 -0700 David Gravereaux 
<davygrvy at pobox.com> writes:
> If heat dissipation using a linear output drive (transistor) is 
> a problem, with a bit of design work and using the direct 
> (unfiltered and rectified) alternator output, you can use an 
> SCR for the drive part.  It dissipates almost no heat...  well, 
> almost, maybe 5-10 watts.  I made a 15 amp 12v battery 
> charger this way.  It worked like a charm.  I can get you a 
> gif of a schematic, if you're interested?
> 
> Basically, you generate a triangle wave from the periods of 
> the input waveform -- start at zero, end high, repeat.  Feed 
> this into a comparator along with the out of an opamp 
> (linear) comparing a 6 volt reference to the output divided 
> by 2.  The feedback resistor is the gain around the drive 
> point.  My recall is kinda fuzzy, but the idea is to fire the 
> scr earlier in the triangle wave to output more current.  
> Because an SCR is either on or off, the only heat it 
> develops is it's forward drop -- chopper style or Class-D 
> as it's also called but with a 4-layer diode
> instead of a linear device.
> --
> David Gravereaux

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