555 EFI again...

[Walter Petermann]

Bruce Plecan wrote:
> 
> From: Walter Petermann <corsaro at brokersys.com>
> Subject: Re: 555 EFI again...
> 
....
> >  The nice thing about the circuit (if it works) is that
> >  only one op-amp is needed for each new function. It should
> >  be easy to add engine temp, air temp etc.
> 
> If this converts voltage to PW, how would one stack Op-Amps
> together to add voltages?.  Or are we talking about something
> that would look like an audio mixer?.  Comments from the EE
> challenged.
> Bruce
> 
Actually, I got a little ahead of myself there...should count to 20
before pressing "send". The circuit was made to control an aux
injector on an existing fe system. To have any hope of working
as a fe circuit, by itself, it would need an rpm input. Then a way of 
multiplying the map * rpm * some constant. Multiplications are a bit 
difficult with op-amps.

As far as adding new sensor inputs to this circuit, this is how it 
works:

Each op-amp circuit is a current source. For the map sensor, the 
current output is (MAP - vr2)/vr3 . As the MAP voltage drops the 
op-amp drains current from the control voltage pin of the 555 lowering
the threshold -> decreasing output pulse duration.

The op-amp current sources can be connected in parallel. Each will 
add/subtract current as necessary according to its own sensor input.

Hope this helps, and if anyone has a KISS circuit for multiplying
voltages or currents we can put that in too. 

 Walter

PS Speaking of audio mixers which I don't know anything about, except,
they are a great source for variable voltages for ecm's. You can tear
all the guts out and just keep the pots and power supply. Radio Shack
sells some basic ones very cheap.

1,2,3.........20  send