Voltage controller?

[rr]

Dan,

If you wanted to convert the 5v MAP to a 12v signal, relative, use an
op-amp. Just use an amp with a gain of 2.4 (12 / 5). Use this in the
non-inverting configuration. The only problem with this is head-room,
most amps won't go to the plus rail.

A better approach might be PWM. Look in the 'incoming' directory for
the files: PWM2.gif  and PWM2.txt (not sure of the exact case).

These are the circuit diagram and writeup for a PWM controller that
can be used with any permanent magnet DC motor. This circuit can
be driven from the MAP with only an Op-amp buffer at the front end.

For more op-amp stuff (ideas), get ahold of a National Semi Linear
databook, or hit their web site for app notes. They have a ton of
stuff on practical uses of op-amps. (AN-20 & AN-31 are good ones).

BobR.

P.S. The files FprErr.gif & .txt also have some novel uses of op-amps.


Daniel Houlton wrote:
> 
> Hi.  Me again.  Sorry, but I've got more questions.  For my turbo, I don't
> yet have an intercooler and don't know when I will.  In the meantime, I've
> planned on building a water injection system using basically a boost
> pressurized tank and a couple pumps to provide a pressure differential to
> inject water after the turbo.
> 
> Instead though, it's very likely that I'll be getting an ERL AquaMist from
> a friend to try out.  This is the $500 job I think.  Uses a high pressure
> magnetic/diaphram pump or something.  I won't be getting the controller
> they sell for it, just the basic system.
> 
> I'm pretty sure I read on their page that the pump pressure is controlled
> by a 0 - 12V signal.  It could be it's just driven by 0 - 12V, but I
> thought it was a seperate signal.  Power is through a seperate 12V
> supply.  Maybe not though.  This is how their controller controlls it.
> How would I produce this signal from a MAP sensor?
> 
> Say I get a 2 Bar sensor.  These are linear from 0 - 5V representing
> vacuum - ~15 psi (over ambient) right?  Now if the MAP sensor put out 0 - 12V
> instead and the pump took a 0 - 5V signal, I could just use a pot and
> direct connect the sensor to the pump.  I need to go the other way though.
> I need to step up the 0-5V MAP signal to a 0 - 12V signal for the pump.
> 
> Any suggestions how to do it?  What about if instead of a 0 - 12V signal
> I need a 0 - 12V power (presumably much higher amps than the MAP can
> supply) source?  What I need is something like a 30 amp relay that can
> supply a variable voltage instead of full voltage or none.  I'm sure
> something like this exists, but I'm (obviously) not an EE so I don't know
> what to look for.
> 
> Oooh!  What about an "electronic" pot?  Something that can control
> resistance from a voltage signal instead of physically turning a dial?  I
> could then provide full, high amp voltage to the pump through a relay and
> run it through this "electronic" pot.  The pot would adjust the resistance
> according to the MAP output.  Map signal goes up signalling pot resistance
> to go down and the pump gets more voltage resulting in higher water
> pressure.
> 
> A seperate Hobbs switch could control the relay to arm the system at
> whatever boost pressure I want.  Is this totally off the wall or is it
> doable?
> 
> thanks
> --Dan