Hi Guys

Can anyone help me with my question?

Im trying to make a circuit with a 555 timer that will allow me to press a momentary push to make button and then latch the output (which i have managed to do).

However I also need to the circuit to be able to switch off an output using a relay or similar when either a external -ve or +ve is detected using the same on/off switch.

I have attached a basic circuit below as to what i i have done so far.

Can any of you guys help me?

Thanks

 

-ve or +ve detected where...??...do you mean the input...do you want input over voltage protection ??

 

Basically what i want is to be able to turn somthing off with the switch using a relay or somthing like that.

Im thinking that when a 12v signal is detected it will illuminate the LED but i can override the signal with my button thus firing the relay and removing power to the LED.

 

I am one of the experts on the 555 around here. Feel free to point me to your posts on them. I am writing several articles for the AAC book using them.

I think this will answer your question...

555 Bistable Multivibrator

Bill's Index (my blog)

 

Hi Bill

Thanks for the responce.

Are you saying that the circuit you posted is what i need? as i dont understand how it will let me overide when a signal is detected.

Thanks

 

I am one of the experts on the 555 around here. Feel free to point me to your posts on them. I am writing several articles for the AAC book using them.

I think this will answer your question...

555 Bistable Multivibrator

Bill's Index (my blog)

follow this dude

 

The circuit I showed is a simple flip flop, but it can also be reset with the reset input on pin 4. I am not sure I understand your requirements, but I think this fills them. Reset on the 555 overrides all other inputs.