One off pulse recognition circuit.

Thread Starter


Joined Feb 14, 2008
Hi guys and girls.
I'm very new to this so please excuse any lack of etiquette or ability!

What I am trying to create is a circuit that can be attached to a striker point and will recognise a pulse and then be able to show that it has happened. For example, I press a button, a pulse of around 28V is generated at a remote point.
(I should point out that this system is already in place.)
What I am trying to devise is a way I could then walk to the remote point and confirm that the pulse was delivered to the striker. I was thinking press a button LED lights up, that sort of thing. So I guess in essence I need a circuit that will store a 28V pulse until I press the button and light the LED.
As I said I am very new to this so apologies for the rambling, I was thinking a circuit using a 555 timer may work.
Any ideas
All help gratefully received.


Joined Aug 8, 2005
If you have access to +5V, you could try something like in the attached. This could also work from a 9V battery with some circuit changes.

Circuit Description
Upon power-up, push switch to set 555 into known state (LED to off).

After which TRIGGER will be high, THRESHOLD will be low.

If positive pulse is received (> 4V), the THRESHOLD (3.3V = 5 * 0.67) will go high and set the output low to light the LED.

The LED will remain on until switch is pressed.

The input diode (D3) is for steering & input protection. The 4.3V zener (D2) will limit the input voltage to proper levels.

The circuit, as is, will require about 1mA from the 28V pulse.

To power this from other than +5V, both R1 & D2 would need to be selected accordingly.