Test Circuit Request: Stop Current Before Wire End?

[starcruiser]

@Spherenot,

The RC network determines the time constant t=R*C, the circuit values posted provide a 10Hz pulse or .1mSec on time.

t = Time

R = Resitance in Ohms

C = Capacitance in Farads

Try a smaller value Cap and a smaller value resistor

Actually you would be better off using a 555 timer circuit in an astable mode.

Try this site

http://www.williamson-labs.com/555-circuits.htm

[Spherenot]

Try a smaller value Cap and a smaller value resistor

Actually you would be better off using a 555 timer circuit in an astable mode.

Try this site

http://www.williamson-labs.com/555-circuits.htm

Radio Shack did not have a 4013 chip the other day.  So, I picked-up a 555 while I was there.  I got it to work and played with square wave sizes using various R & C sizes.

The next day I made a mad lunchtime dash to the other local(ish) electronics store with 9-5, M-F only, hours and got my two NTE4013B chips to pursue this circuit.  When I used smaller C and R, on the pulse out side of the circuit, my nice vertical square wave turned into curly mess.  So then I started playing with the R's and C on the switch side.  I went to bed as dumb as the post I was when I woke up that morning.

Thanks for the link.  I will check it out.

[Loki67671]

Try a smaller value Cap and a smaller value resistor

Actually you would be better off using a 555 timer circuit in an astable mode.

Try this site

http://www.williamson-labs.com/555-circuits.htm

Radio Shack did not have a 4013 chip the other day.  So, I picked-up a 555 while I was there.  I got it to work and played with square wave sizes using various R & C sizes.

The next day I made a mad lunchtime dash to the other local(ish) electronics store with 9-5, M-F only, hours and got my two NTE4013B chips to pursue this circuit.  When I used smaller C and R, on the pulse out side of the circuit, my nice vertical square wave turned into curly mess.  So then I started playing with the R's and C on the switch side.  I went to bed as dumb as the post I was when I woke up that morning.

Thanks for the link.  I will check it out.

Spherenot,
One thing you will have to do is pay attention to the current ratings, source and sink, of the flip flop when you "play" with your R values. The adjustment for the pulse duration is the RC network on the output. The Frequency is directly related to how fast you close that pushbutton and the logic component, i.e. the 4013 in this case. While this circuit is certainly useful in the lab, you'll probably get tired of having to push the button.  Take your R value down and C value down on the output end to shorten the pulse duration. Frequency is another story. An oscillator of some sort will be necessary for frequency adjustments.

Regards

JT

[Spherenot]

My goal is a 20 nanosecond pulse.  The spec-sheet that came with my 555 indicates:

Maximum frequency in astable mode: 2.1 MHz

If my calculations are correct, this is 476 nanoseconds per cycle.  I already know about putting the diode across pins 6 & 7 to get < 50% duty cycle, but I am not sure if I can squeeze a 4.2% duty from the edge of the 555 specification envelope.

I was hoping that I could do this with simple solid state circuitry.  Will I need something exotic and expensive to achieve a 20 nanosecond pulse?

I don't know about stopping the current before the wire ends, but I think I am going to stop this test before it ends.  WTF am I going to do when I get my 20 nanosecond pulse anyway?  It's like giving a hooker to a seven year old. 

[Grumpy]

Simple.