Hi I am of need of a circuit operation for the following circuit. I beleive after building it the not gates act like a nonstabke vibrator but I'm not sure how excalty this circuit works. The counter part I do understand.

 

Top left is an oscillator, bottom left is just a buffer that when the button is pressed drives the led's to ground and turns them on. The oscillator obviously clocks the counter, the button press also stops the oscillator pausing the counter.

 

Yes , but how does the configuration in the left produce the oscillations

 

R1 and r2 charge c2 forming the timing circuit for the input to the osc amp.

 

R1 and r2 charge c2 forming the timing circuit for the input to the osc amp.[/QUOTE

So the parallel combination of r1 & r2 charge c2. What about r4 and c3

 

That oscillator isn't what you think it is. IC1D and IC1E form a non-inverting buffer with hysteresis, which can act as a latch. It is IC1A with feedback through D1 and R2 that turns it into an oscillator. The original designer is playing some games with the resistor value ratios. For example, R1 can override the hysteresis feedback coming in through R2, and R4 might figure in there depending on the output state at pin 2.

ak

 

If possible can you eblaborate on that because I have never seen a schmitt trigger configuration like this before.

 

What a neat circuit; with insufficient + bias at pin 1 , nothing moves. Charge up C3 & ckt. oscillates at about 50 Hz. As C3 discharges it takes + bias longer to recover & at about 8 sec. later C3 down to 2.5 V , osc. stops. Vcc = 6V. IC = 4009.

 

As the overall circuit slows down, R3 always discharges C3 through D1 at the same rate. If you tied the three inverters (pins 13, 3, and 5) to pin 10 instead of the switch, then the LEDs would blink off briefly when changing from one LED to the next, and as the circuit slows down the off time would be constant and the on times would get longer and longer until the circuit stops on its final value. VERY nice.

ak

 

Thx guys those are excellent explanations

 

Here's what it looks like:

 

Here's what it looks like:

Yes but this circuit is not easy to breadboard as the all the leds do not light up

 

They all light up, but one at a time; that's the intent of the circuit.

ak

 

They all light up, but one at a time; that's the intent of the circuit.

ak

I think that he is saying that its hard to breadboard because of many connections he has to do which results in some LEDs not lighting up because of improper connection.

 

yes

 

That's part of the "fun" of electronics, and it never goes away completely. About 2 weeks ago my hands thought they knew more than my brain. I love the smell of fried transistors in the morning.

ak