AquaMist pump (was: Re: Voltage controller)

[Daniel Houlton]

rr wrote:
> 
> OK, finally got into this site (it can be reeeaaallll slow). This is
> an interesting pump. Basically, it is a solenoid driven pump. Figure
> a bicycle pump with a magnetic solenoid pulling back the rod, then a
> powerful spring returning the rod to the original position to pump.
> The pump stroke is run at about 50Hz.
> 
> There are electronics built into the pump itself, no separate
> controller.
> According to the schematic, the input siganl is just an on/off as the
> water is required. They use a pressure switch.
> 
> Bottom line,  Dan, I don't think that you need anything else to drive
> this pump. It's all self-contained...


Yeah it looks that way, but it can still be controlled to vary the
amount of injection by controlling the pressure.  The basic system
comes with an on/of pressure switch which means you get all or none.

Their upper-level kit includes their fuel injector control box which
also has an output for this pump.  It increases pump pressure and 
therefor the amount of water injected as the boost pressure goes up.

That's basically what I want to do.  Provide a variable voltage signal
(looks like 0 - 12V) to increase water pressure as boost goes up.  If
I could get this signal from the 0 - 5V a MAP sensor gives, I can get
a nice water injection curve instead of turning it on full blast at X
psi with a pressure switch.

Use the pressure switch that comes with the pump to arm the system 
and prevent injection before 3 psi say.  Then map the MAP output so
that the pump gets about 6V (half pressure) at say 3 psi and then ramps
up rapidly to deliver 12V (full pressure) by 8 or 9 psi.

Someone mentioned an op-amp could do this.  Also a 555.  What is a
555?  Is that a particular op-amp?  I remember it being referred to as
a timer someone used to drive and additional injector from the signal
to a stock one.

For now I'll start studying op-amps.  Thanks for the help.

--Dan