-12vdc signal to switch automotive ignition amplifier

[rab986]

High guys... new to the sight and glad that I found you.

To the problem....
I currently have a -12vdc to ground signal that i need to trigger an ignition amplifier which can be fired 1 of 2 different ways.
1. it can be triggered if a certain resistance level of 400-1300 ohms is met between 2 pins or...
2. it can be triggered if a pin to ground contact in interupted. (break of ground)
Whichever way I go it needs to be able to fire at a rate of about 600 - 700 times per second.

Thank you in advance
Steve

 

[OperaHouse]

You could usp a (gasp)555. I can't believe I said that, hate that device. A little easier to use by a neophite is a TL494 and these can be found in most old PC power supplies. You can easily control the duty cycle and frequency sperately, a pain with the 555. I doubt that you need a -12V signal.

 

[rab986]

I don't "need" the -12v pulse signal but it is all I have so I "need" it to fire my ignition amplifier which is my problem. I will look into both of these timers and see if I can figure out how to make them work. Any other input would greatly be appreciated.

 

[coconutalley]

rab,
You problem is vague. I'm assuming that you have -12V but the amp needs something like +12V? One possibility is to use an optoisolator?

 

[itsmoked]

Why a minus 12V in an automotive system?

When someone mentions 555's here, (shame on you OperaHouse!! Go to your room.

),
I and others will always pipe in with, "just use a microcontroller". Microchip has 6pin SOT23-6 controllers that would let you do all sorts of stuff to/with your signals.

If you want more suggestions I suggest you flesh out your description a bunch more.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[MikeHalloran]

I don't understand where you would _get_ a -12V signal in a car.



Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

Other side of the transformer Mike...

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[MikeHalloran]

Ah.

Operahouse and I thought he was talking a gated oscillator ... but he's talking about the rep rate for a single pulse inverter/switch, to replace breaker points.

... brain fade.



Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

Who knows... I was kidding on the transformer, you may be entirely correct!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[rab986]

How am I getting a -12vdc signal?
It is the signal that I am getting from the factory optical distributor and since I do not have the ECU computer I am trying to find a way to fire my ignition module with the only signal that I have. I could probably take the opto isolator out and machine the shaft putting cam lobes on it and simply use points but where is the challenge in that?

 

[rab986]

I will check out microchip and see if I can find the right micro-controller for my application.

Being a "neophyte"... the first thing that came to mind was a relay of some sort that would be reliable at a rate of 40000 cycles per minute. This could be used to imulate a breaker point system but is there a relay with that kind of duty cycle?

 

[OperaHouse]

How did you measure that -12V? If you had a scope with an AC input, a narrow pulse that went from +12 to ground would look like a -12V signal. Your easiest choice is the TL494/594 if you can find one. I love microchip, but it is not something to start out with from ground zero.