help with parts

[Dwayne]

Total know nothing here
I have an idea but could do with some help finding the parts to work out a
circuit.
first off I need to clip a wire onto a HT lead on a car engine which will
give me a pulse once every 4 turns of the engine (or I could put it on the
main feeder lead which would then pulse every turn either way is fine )
So this HT signal would need to be converted to a safe usable voltage: I am
thinking small transformer with a voltage regulater or a optical device or
even getting the signal from the low voltage area of the ignition (not ideal
I want the unit simple to clip on or off and for any make of car).

Next this signal would need to be fed to a PWM, I am thinking that I would
need to change the pulses to a variable voltage which could be used to
control a simple 555 based pwm circuit. what would be the simplest way of
achieving this?

Then the output from the PWM would need to be fed into a transistor capable
of running a motor of around 20amps.

So the block diagram would look something like:
HT pickup - useable pulse - analogue signal - PWM - transistor - motor

as you may have guessed I want a motor that runs faster and slower dependant
upon the rpm of the engine.
thanks in advance for any help.

 

[Andy P]

Can I ask what for? Just a big guess here...but I would suggest
spending the money on the turbo or supercharger. If your trying to make
a hybrid type of setup, this is not the way to do it. If I'm way off
base, then I appologize.

In answer to your question...

Inductive pickup (like on a timing light)- schmitt trigger -
(optional)optoisolator -frequency to voltage converter-pwm
controller-high current darlington-bigger transistor (probably a fet of
some sort, check the specs to be sure).

Honestly, if your a know nothing as you put it, this may not be the
project for you. Your going to be dealing with massive voltages on one
side, and massive curents on the other. 100miliamps and/or 30 volts is
enough to permanently stop your heart. On top of this, a failure in the
system could mean a total failure in any one of the dozens of systems in
the car. It really is a safety risk not only to you, but to anyone
around you when it happens while your driving.

 

[Dwayne]

Can I ask what for? Just a big guess here...but I would suggest
spending the money on the turbo or supercharger. If your trying to make
a hybrid type of setup, this is not the way to do it. If I'm way off
base, then I appologize.

your spot on but I fancy experimenting and will continue despite the
previous rather disapointing results from electric superchargers. You never
know i may just come up with something no one has thought about.

In answer to your question...

Inductive pickup (like on a timing light)- schmitt trigger -
(optional)optoisolator -frequency to voltage converter-pwm
controller-high current darlington-bigger transistor (probably a fet of
some sort, check the specs to be sure).

thanks have found some some parts from your description.

Honestly, if your a know nothing as you put it, this may not be the
project for you. Your going to be dealing with massive voltages on one
side, and massive curents on the other. 100miliamps and/or 30 volts is
enough to permanently stop your heart. On top of this, a failure in the
system could mean a total failure in any one of the dozens of systems in
the car. It really is a safety risk not only to you, but to anyone
around you when it happens while your driving.

OK maybe know nothing was a tad understating myself. I do understand the
dangers of the voltages and currents involved (just one of the reasons I
wanted a non intrusive method of getting the signal from the car) I have a
little experience with electronics, not a lot admitedly but some.