I used to play around with 555 timer circuits up until I retired about 15 years ago but have become a bit rusty on it now and am seeking a bit of help.
I also used to have access to bread-boarding and heaps of components to try out different things but that is not now readily available. The particular application I am putting together does not work on a pulse as such but is looking at a switch position and needs to generate a delay based on the switch position. It may be possible for some clever chap to achieve the delays simply with diodes, resistors and capacitors.
The first diagram is quite straight forward but as a possible variant it would be nice to have the 555 timers energised when the switch is closed and de-energised when the switch is open so there is no residual standby current in the open switch position. I will probably use a CMOS 555 timer so if the variant isn't possible to achieve then residual standby current won't be a huge concern.

 

When the input goes low, output 2 will go low .

 

This is my attempt:

 

Hello Albert.
I need the input to be the opposite sense to what you have nominated as per my initial concept drawing.
Thanks
Ian

 

You are aware of the 556 I assume?
Max.

 

Hello Albert.
I need the input to be the opposite sense to what you have nominated as per my initial concept drawing.
Thanks
Ian

As the '555 needs a negative going trigger then that's the way it needs to be. You can use your positive going trigger and an inverter (chip or transistor) to drive the circuit.

 

You are aware of the 556 I assume?
Max.

Max
I think from memory the 556 is a twin 555 in a single package.
Ian

 

Max
I think from memory the 556 is a twin 555 in a single package.
Ian

Yes.
Just cuts down on real estate.
Max.

 

This is my attempt:
View attachment 161833

Hello Albert
I had a play with your suggested circuits and I am happy with your suggestion for Output 2. I have modified it slightly as per the attached file to cater for my particular needs and it works OK.
The only problem I have which you may be able to assist me with is when the circuit is powered up with S1 open the Output goes high for a second or two which means the relay it is going to control will also be energised and I don't want it to be until S1 is closed. Once the power is on and it has done it's little pulse it settles down and works as per the Input and Output diagrams.
Would you have any suggestions as to how I can hold the output low at switch on with S1 open?
Thanks
Ian

 

Connect C4 positive to the positive supply and C4 negative to '555 pin 2.

 

Connect C4 positive to the positive supply and C4 negative to '555 pin 2.

Albert

I will give it a go and see what happens.

Cheers
Ian

 

Connect C4 positive to the positive supply and C4 negative to '555 pin 2.

Albert

That worked a treat thanks. No more spurious unwanted output excursions.

Regards
Ian