Duty Cycle Help???

[shaneshane1]

Hi, i have some questions about Duty Cycle.

eg: i know that if a fuel injector has a duty cycle of 60%, then it is on 60% of the time and of 40%.

but what im not sure about is, in what time period does the duty cycle happen, meaning does the 60% duty cycle happen every second, every half a second, every minute?????????

or does it depend on the device eg: fuel injector, printer, etc.

 

[audioguru]

The fuel injector squirts fuel when it is supposed to squirt fuel. On the intake stroke of the engine?
Its duty-cycle occurs when it squirts fuel and determins how much fuel per squirt.

 

[kchriste]

Technically, a duty cycle is not dependent on the time period. ie: one second on with 9 seconds off is the same duty cycle as 1 hour on and 9 hours off: 10%.
In practice, most parts, such as solenoids, also spec the max time period when discussing duty cycle. The "off" time gives the solenoid time to cool off so if the "on" time was very long, the device would overheat and fail before it got to it's cooling off time.

 

[shaneshane1]

The fuel injector squirts fuel when it is supposed to squirt fuel. On the intake stroke of the engine?
Its duty-cycle occurs when it squirts fuel and determins how much fuel per squirt.

not entirely, on my car i have a airflow meter which measures the air been sucked into the engine, and that sends the infomation to the computer which sends the info to the injectors, the injectors then shoots the right amount of fuel to the intake valve waiting to suck the fuel in, without the airflow meter the car simply wont run because the injectors wont know what to do.

so im assuming that when the car is at idle, there is a duty cycle eg: 20% at a given time frame 1 second?

so it might be open for 20% duty cycle every second?

that was just an example, and is not correct at all.


so im just wondering as i excelerate does the duty cycle increase and the time frame stay the same.

eg: 20%, 30%, 40%, 50%, etc and still every 1 second

 

[kchriste]

so im just wondering as i excelerate does the duty cycle increase and the time frame stay the same.

Of coarse not. Your fuel injector squirts during every intake cycle of the cylinder on the engine so as RPM increases the time frame between squirts gets shorter. The duty cycle will vary to keep the proper fuel/air mixture for a given engine load, RPM, ambient air temp and pressure etc.

 

[Roff]

This article has a good explanation of injector duty cycle. If you Googled "fuel injector duty cycle", you should have already read this article. If you didn't Google - shame, shane!

 

[Dean Huster]

And then when you look at the duty cycle equations for the 555 timer, it dashes your electronics education to bits as you try to figure out why when you're trying to lengthen the "ON" time, the duty cycles keeps getting smaller. Don't know what Signetics was thinking about back then.

Dean