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[on:]

Hi!

I'm planing to build rpm limiter for my motorcycle. This is the schematics and code that I wrote, and I'm interested would this work:



This is the code:

Code:

const int rpmPin=2;
const int killSwPin=0;

unsigned long lastPulseTime = 0;
unsigned long rpm = 0;

void setup()
{
pinMode(rpmPin,INPUT);
digitalWrite(rpmPin,HIGH);
attachInterrupt(rpmPin,RPMCounter,RISING);

pinMode(killSw,OUTPUT);
}

void loop()
{
if(rpm>=7000)
{
digitalWrite(killSw,HIGH);
}
else
{
digitalWrite(killSw,LOW);
}



}
void RPMCounter()
{

  unsigned long now = micros();
  unsigned long interval = now - lastPulseTime;

  if (interval > 2000)
  {
     rpm = 60000000UL/(interval);
     lastPulseTime = now;
  }  

}

RPM reading is based on this schematics:
www.sportdevices.com/rpm_readings/index.htm

Thanks!

[Reply #1 on:]

I'm not familiar with the symbol you're using for T1 - is it some form of transistor? If so I guess you're planning to override the points by holding the coil -ve to ground. While that will certainly kill the spark, it'll also overheat the coil pretty quickly.

[Reply #2 on:]

That is a SCR.

How should I overheat ignition coil, when all the voltage goes to the ground?

[Reply #3 on:]

Does anyone know?

[Reply #4 on:]

PeterH is thinking you're using an automotive type coil that receives power from the battery. You're apparently using the type of coil that generates its charge from a magnet on the flywheel. No, there's no risk to the coil for what you're doing.

[Reply #5 on:]

I would be interested in this for an automotive application any way to get over the overheating issue?

Lance

[Reply #6 on:]

PeterH is thinking you're using an automotive type coil that receives power from the battery. You're apparently using the type of coil that generates its charge from a magnet on the flywheel. No, there's no risk to the coil for what you're doing.

Thanks!

[Reply #7 on:]

I would be interested in this for an automotive application any way to get over the overheating issue?

You reduce the amount of time that current is flowing through the coil (the "dwell" time). It should only be energized for a very short period before you switch off the current / create the spark. Just take a close look at your distributor and you'll see the the breaker points are only closed momentarily.

There are special purpose IGBTs/mosfets designed for this type of high voltage current switching; a dig around Fairchild Semi's site will list a number of them. Or use the google, etc.

[Reply #8 on:]

PeterH is thinking you're using an automotive type coil that receives power from the battery. You're apparently using the type of coil that generates its charge from a magnet on the flywheel. No, there's no risk to the coil for what you're doing.

Yes, I was thinking this was a conventional automotive car ignition system. On these systems, pulling the coil -ve low would result in a lot of heat being dissipated into the coil and is a good way to burn them out.

If this question is actually about a magneto-based system then all you'd be doing it shorting the magneto output to ground. I don't know whether that would be safe to do - perhaps it is.

[Reply #9 on:]

PeterH is thinking you're using an automotive type coil that receives power from the battery. You're apparently using the type of coil that generates its charge from a magnet on the flywheel. No, there's no risk to the coil for what you're doing.

Yes, I was thinking this was a conventional automotive car ignition system. On these systems, pulling the coil -ve low would result in a lot of heat being dissipated into the coil and is a good way to burn them out.

If this question is actually about a magneto-based system then all you'd be doing it shorting the magneto output to ground. I don't know whether that would be safe to do - perhaps it is.

On that principle, works kill switch on motorcycle, so it would be safe!