Hi I need a circuit that when you press the switch the led will stay light. Say 30 sec and then turn off till sthe switch is pressed agen

 

Something like this might work:

You can adjust the resistor and capacitor to control how long it stays on after release.

John

 

Something like this might work:

You can adjust the resistor and capacitor to control how long it stays on after release.

John

Thanks John I can't see the image on my iPhone but il check
It out on my computer soon thanks

 

That's an old picture from a previous post here. I don't know why it came out so small. While I am trying to fix that, here is the link to the original post:
http://forum.allaboutcircuits.com/showpost.php?p=167417&postcount=5

Fixed it. Note, it is a logic level mosfet.

John

 

That's an old picture from a previous post here. I don't know why it came out so small. While I am trying to fix that, here is the link to the original post:
http://forum.allaboutcircuits.com/showpost.php?p=167417&postcount=5

Fixed it. Note, it is a logic level mosfet.

John

i see you are also saying you can di it with a 555 timer would you have anything on that scamatics

 

How complicated do you want it to be? Do you want a "snap" action or is a gradual fading off ok? What current will the LEDs draw? Almost any analog circuit will be a variation on the RC circuit I showed.

John

 

How complicated do you want it to be? Do you want a "snap" action or is a gradual fading off ok? What current will the LEDs draw? Almost any analog circuit will be a variation on the RC circuit I showed.

John

Hello a gradual fade of is fine i just need to run 5 led using forward voltage of 2.8min 3.0 typ
i also will need to run a 3v buzzer on the same circuit picture this circuit as a door bell you press the button and it light up and makes sound. but unlike a door bell it stayes on for a few seconds longer than the button is pressesd.

 

Q1 is a generic N-channel, logic-level mosfet transistor.

You will need to consider your supply voltage. Will it be 5V (nominally) or 3V?
Can post a flow chart or block diagram of what you want to do. "I also want to..." can be confusing.

John

 

I can put as much as 12v into this circuit as it will be running off a variable powersupply so i can change it down to 3v or up to 12v what ever makes it easier for you to do thanks

edited**** sorry was mentt to say the picture is of what the circuit looks like now with no timing at all

 

what about this i i use this layout but were pin 3 comes out of the 555 timer i split so one cable goes to the led and the other goes to the buzzer this way i can put diffrent resisters values on for the busser and the leds that will be in series