HELP with 555 timer

Does anyone have a schematic for a count down timer (5-10 mins) using a 555 chip?

If the timer is activated by a push button switch, is it possible to make it so that when I push the button it will keep the timer going even after the button is released?

 

What I am looking to make is a count down timer, where when I press a button, the circuit will let me know when the time has expired. I would like to be notified either by a flashing led, buzzer or both

 

can a piezo buzzer be used in place of the sonalert? if I integrate this into a circuit that I have and a push button has a fuction already. Can I use that same button to silence the alarm? If I only needed one LED how do I make the changes to the plan?

 

Im in New York. I tried your timer using the 555. I dont want to attach the sonalert so I stopped after I installed the 1k resistor on the right side of the shematic. I only have one switch.

when I plug the battery in the red led comes on with the switch pressed. after 3 mins (I have 165k resitor) nothing happens. when I touched the battery it was hot. what am I doing wrong? Do I have to complete it with everything installed in order for it to work?

Alex

 

i followed the plan. i put a 1000uf cap instead of a 10uf
i also used a 15 k resistor fot the "rt". i followed the values for the kitchen timer project . im burning the 10k resistor. what seems to be the problem. can i burn out the timer if i keep trying.

 

Hmm, feel the 555 timer, is it hot? Even if it is slightly warm, it usually means the timer is a dud. What are you building it on, breadboard? Stripboard? If you have a short on the output, the timer could be damaged, this could lead to the hot battery you noticed.

 

Bill

I took everything apart and built it again. the 10k resistor on the "A" side of the capacitor is smoking when i apply power to the curcuit. I'm using a switch from "GND" to "trigger" and i also configured where i use a switch connecting "GND" to the "A" side of the capacitor. both with the same results.

when I plug power in the red LED turns on, when I press the switch the green LED comes on then after a few seconds i smell the resistor burning.

 

Im using a 9 volt batt. Im using a 556 because I want to use this in con juction with something else. (i know a 556 is 2 555 in one) Im only testing the timer by itslelf. i havent even begun to build the second part of my project. Im going to triple check the values of all the resistors.

 

Make sure you have the correct pin out for the 556. It isn't the same as two 555s stuck one on another; there are shared power pins, for example. Also, make sure you're not using the 558, which manages to fit 4 x 555s in one chip, but has to combine some lines into timing and only has one reset/control voltage IIRC.

 

yes i have a volt meter. im using the "#5 pin" on the 556 as the out. Im using a Radio shack 556cn (part # 276-1728.

the original plan called for a 10 k resitor. Im now using a 15k as per your instructions, Bill

No more burning, but it smells like something is burning and the cap is getting hot (C1)

How are the lights supposed to "flash", if at all. I plug in the 9v batt and red LED is lit. I press the switch Red goes out green turns on.

 

pls tell what Is the maximum Freq. of 555 Ic........!