2 x 555 monostable loop

[abuhafss]

Hi

I want to make a circuit having two 555s monostable with following features:

1) U1 should be triggered automatically at power ON.
2) When output of U1 goes low, U2 is triggered.
3) When output of U2 goes low, U1 is triggered.
4) Hence the cycle is repeated continuously.

Here is my schematic. The first timer is triggered at power-on and it also triggers the second timer. However, the second timer is also triggered at power-up and also it does not triggers the first timer.

Any help would be appreciated.

 

[(*steve*)]

Is there any reason that you can't use a free running oscillator for this?

 

[abuhafss]

Is there any reason that you can't use a free running oscillator for this?

Yes, actually both these timers form a section of the main circuit which controls them. And these timers have to perform there respective jobs alternately.

 

[jpanhalt]

What type of control signals are being used? The schematic you presented looks kinda fixed.

A single 555 can be configured to give independently adjustable on and off times within the constraints of the device.

Why do you have to use a 555?

John

 

[abuhafss]

This partial circuit is to give you an idea.

The first timer issues a pulse of about 15 seconds.
Then the second timer issues a pulse of about 3 seconds.
They both form a cycle of 15+3 seconds which is to be repeated continuously.

And their reset pins are actual connected to the output of a 3rd timer which controls how long the cycle is to be repeated (20 -25 times).

p.'s: The restriction is that no PIC has to be used.

 

[(*steve*)]

I would connect the first 555 up as an astable running ON 15 seconds, OFF 3 seconds.

I would connect the second 555 as an inverter.

I would connect both reset lines together and back to the rest of the circuit.

Or I would alter the second part of the circuit to allow a pulse in the opposite direction (a transistor and a couple of resistors most likely)

 

[abuhafss]

I would connect the first 555 up as an astable running ON 15 seconds, OFF 3 seconds.

Got the point. But how, to handle the case if for example the first timer is to issue a pulse of 15 sec and the second one to issue more than 60sec say 300sec?

 

[(*steve*)]

Then you use something other than a 555. A microcontroller may be a simple solution. (Use an ATtiny -- it's not a PIC )