Pulse Generation Problem

[hyedenny]

I hope we get an A for your project...

 

[ecid]

more?

:lol:
An "A" ? Scoring is not necessary for me.....
What important now is how can i design the pulse shaper....

thanks

 

[ecid]

more?

hyedenny :
An output reading from flying wheel to measure rpm, is it a high speed signal?

In your previus post (pulse.jpg), how can i determine the value of the components (resistor) ? And what type of transistor would be used?
Also in your newly post (monostable.jpg) what kind of transistor(s) is used?
what's the difference between both configuration?

The parallel interface to the pc is only for displaying the speed in the pc's monitor. What is actually the PIC needed for?
Is the PIC also for controlling the motor movement ? (although for my project, it is not necessary) ?

If i use 555, how is the configuration? (I think it's provided in the 555's datasheet, isn't it?)

 

[hyedenny]

It depends on the circuit you use. I would guess that a signal of less than 10Hz could use its period as a measurement. But since your messing with the pulse width, just stick to a frequency measurement.

The transistors in either circuit can be any handy NPN, like a 2n3904 or 2n2222. The resistor and capacitor values, R & C, are determined as I mentioned before, by t=RCln2.

There are a zillion tutorials for the 555 timer on the web. Theyre VERY easy to use. Configure it as a "monostable multivibrator" sometimes called a "one-shot." The 555 is probably a more stable circuit for doing what you want to do (whatever that is!), but I would still use a microcontroller, and take care of all your needs in one tidy package. It takes a little time to learn how to use them, but you'll open a whole new world of possibilities once you do.

 

[Nigel Goodwin]

Re: more...

Nigel Goodwin :

That's the problem.... it has been specified in my project that i must altered the pulse width to fullfill the interrups requirements, so the pulse will be 100us.

I think you've misunderstood the reason for that comment?, it's NOT to make the pulse narrower, it's to ensure that narrow pulses are at least that wide, to give the interrupt system plenty of time to respond.

 

[phalanx]

A oneshot (either 555 based or specific monostable multivibrator IC based) will work fine for generating the minimum pulse width.

I think you should do everything in the microcontroller. Setup two pins on your microcontroller to interrupt on change. Feed your unconditioned pulse into one one of the interrupt pins. In the ISR, generate a pulse that satisfies the timing requirement of your assignment. Connect that output pin to the other interrupt on change pin you configured. The PIC will effectively trigger itself and you can then run any other code that you required to do. Then you will have a complete solution in one tiny IC!