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I am building a CPH System with an old Volkswagen TDI diesel engine.
The original computer for this engine is missing and actually I don't want to use one
anyway as I'm feeding a 50hz grid with an asynchronous
generator running at constant rpm and load.

The original computer of the engine feeds the hp pump with a PWM signal of 8 to 10 volts and a frequency of 200 - 400 hz between idle and full load.
I am using an embedded windows platform with FlowStone as the software for the whole system, (thermal switches, engine control, pumps ect.) and it is able to generate a PWM Signal, but I don't know how to boost it to the desired signal strength for the diesel pump.

Now my questions are:
Can a soundcard hocked up to a switching amp that I have laying around, be used to generate the needed 8-10 volts PWM signal? If so, do I have to use a diode to suppress the sinus wave or is it irrelevant for the electro magnet mover(or whatever it is called in English) in the diesel pump?

I hope someone of you guys can enlighten me on how to (cheaply)generate an adequate PWM signal.

Thanks,
Klaus

Oh please guys, someone surely knows this stuff.

OK, maybe this helps a bit.
The PWM signal goes to the fieldcoil magnet which turns the lever on the right.
Based on the wire strenght, it looks to me that quite a few Ampers are needed.

To reiterate the question:
Can the PWM signal that I generate with the software be brought to adeqate strengt
via a soundcard and a switching amp?
The Tripath amps I got can be run with a 12V supply which would prevent over voltage.

I will be glad for any hint.

Klaus

You didn't think of just switching a mosfet to control it? Just need a suitable power supply from there, and don't forget the flyback diode on the coil too.

I think the name you are looking for of the coil you have there is a solenoid.

Thanks for the reply Dakiller,
I thought about using a FET, but since I got so many switching amps laying around I thought I may
as well use them.
In the case of using a switching amp, would I still need a flyback diode?

I guess my bigger concern is the internal soundcard. Is there anything about that type of signal
that would damage it if used 24/7. The diesel engine needs to stay between 1540-1570 rpm.
Only in this range does the asychronus motor that is hooked up to the diesel engine feed the grid.
If the system falls under this rpm range the generator becomes a normal e-motor drawing 22kw/h from the grid.
Insted of getting money for feedign the grid I would loose allot. Actually about $3 an hour.
So I can not afford an unnoticed low rpm running for weeks.

Greets,
Klaus

Hello, nice project.
Once you get it working you could try enhancing your engine:
http://www.panacea-bocaf.org/hydroxygas.htm

Good luck
Alex

There's also Paul Pantone's GEET, that's a proven combustion-enhancing exhaust-cleaning technology that should have been standardized ages ago.

Cheers
Alex

Thanks Alex,
actually a SPAD system on diesel engines, that is used by many French Farmers is saving
much more than the hydroxy kids. It is easy to build and the savings are in the range of
25-50% depending on the engine. Panacea-bocaf has a bunch of info also on the SPAD.
We get about 0.20 Euro for the KW/h here in Germany if we use locally produced vegetable oil.
That means free heating from the coolant and exhaust gas for our homes. If an efficient diesel
engine is used with a SPAD system on it we can actually make money. Unfortunately a combined-power-heat
system in the size I am building it cost at least 20000 Euro, that's why I am building
it myself. Still way to go though.

Greets,
Klaus

Hello Klaus,

You can use mosfets to "amplify" the pwm signal from your soundcard.

I suggest providing 12Vdc, buffer this with say an elco of 4700uF/25V,
don't forget the flyback diode.

I attached an example injector driver output circuit.

You need to modulate the pwm duty cycle to effectively change the opening times of the injector.
I'm not sure if in the automotive industry if they make a difference between the pull-in current and hold currents for an injector.

Regards,
Rudolf

_________________
Rudolf Broertjes

Thanks for the hint on the SPAD, will look that up.
Hope your project goes smoothly
-Alex

Thanks Rudolf,
I gues this is what I will use.
Do you think that the soundcard is OK with a constant PWM signal.
PWM looks to me like a square wave signal without the negative wave.
I thought I read somewere that audio equipment does not like square waves
for whatever reason.

Klaus

I found this very simple booster schematic on the net. Is there any advantage on the one
that Rudolf posted over this one?

Problem with using a soundcard output is that it's hard to encode a duty cycle into it, since the output of basically every soundcard out there AC coupled.

How about this? Feed a class D amplifier a constant frequency sine wave from your soundcard, but vary the amplitude of it. Put the output of the amplifier into a bridge rectifier (you might want a resistor in parallel with it, to keep the amp stable) and feed the actuator with the output of the bridge rectifier.

This should give you a variable, "sort of" DC.