I need some help….Thank you

When a ground (input) is applied (via a switch) monetarily or indefinitely, I need the output to provide a single output pulse of ½ second (or so). The output can be either positive or negative. Once the switch opens the cycle will repeat itself.

This may be simple to most of you but this old man needs some help.

 

You need what is known as a monostable multivibrator.
You can do this with any one of these TLC555, 74HC123, CD4538 or similar devices.

 

What supply and signal voltages do you have?

 

5V supply

 

Below is the LTspice simulation of a typical 555 one-shot circuit.
It generates a ≈0.5s output positive pulse for any length trigger from the switch.
Any 555 type IC will work (they come with several different prefixes such as uA, LM and NE but they are all the same.

 

Thank you for your quick response.
I will build it and post my results.
Brian K

 

A one-shot won't give you a second pulse when the trigger is removed. It only generates a pulse when the trigger is pulled low (when the green trace goes high in the simulation above). I think this can be solved simply if you really need that pulse when the switch opens as well as when it closes.

 

I bread boarded the circuit “CRUTSCHOW” detailed above. It works as detailed.
However, I need to apology to all. The requirement is to provide a 0.5 sec. output pulse when the switch opens (ground is removed).

Brian K

 

So, is that an output pulse *both* when the switch closes and opens, or only when the switch opens?

ak

 

When the trigger switch opens (ground is removed), the output is a one pulse of 0.5 seconds.

Brian K

 

Here is a quickie, 1-transistor circuit. The trailing edge of the output pulse will not be nanoseconds-fast, more like milliseconds.

ak