Count-down clock is supposed to make a sound every minute?

Thread Starter

Mrjesus

Joined Jan 15, 2017
6
I have a question about 555. I am trying to create (circuit diagram) a 5 minute count-down which is supposed to make a noise (buzzer) EVERY minute. So when the timer reaches 4 minutes it will make a noise and it reaches 3 minutes it will make a noise.

I have tried different thing circuits I found on the web but none of them really do what I need. Can someone link me a page that could possible help me with this?
 

#12

Joined Nov 30, 2010
18,217
No, it's a custom design. That's why engineers were invented.:D
Beeping every minute can be as simple as a 555 timer. If you want it to count and know when to stop, you need a second chip.
 

#12

Joined Nov 30, 2010
18,217
I just can't remember which is the, "count by ones" chip.:(
Somebody else will know it and post it pretty soon.
We also need to know how accurate it needs to be and what is the maximum number of minutes required.
There are several ways to do it. Preset input and an actual count-down or a counter that counts up and stops when it's full, etc.
 

AnalogKid

Joined Aug 1, 2013
9,189
How long does the buzzer buzz?
What starts the circuit?
What restarts it after it runs through one cycle and then stops itself?

If you want an accurate minute, a 555 is very poor at long time intervals. Plus, it's first 1/2 cycle after power up is longer than the following ones.
For more accuracy, use a 32 kHz watch "crystal". But to count that down to 1 minute is a 21 stage counter, a minimum of 2 chips. There is an old CMOS single-chip 24 stage counter part, CD4521, but I don't know if it still is available. Also, there are 60 seconds in a minute, not 64, so decode gating is needed.
Someone is going to suggest a PIC/Arduino,whatever.

If you have an old battery-powered wall clock, the kind that runs on a single AA or AAA cell, the guts can be used to make a 1-second clock signal with much more accuracy than a 555. The circuit has been posted here many times.

ak
 

AnalogKid

Joined Aug 1, 2013
9,189
Starting with a 2 ppm (pulse per minute) clock source, a 4-bit binary counter will do most of the work. The Q0 output can drive a CD4093 monostable circuit (maybe nothing more than an R-C and a small FET) and buzzer, and the extra gates can disable the counter after five output pulses.

Now, about that 0.0333 Hz clock ...

ak
 
Last edited:

Bernard

Joined Aug 7, 2008
5,783
Two 555's or 1 556, first 5 min. a-stable osc. second one , one sec. beeper driver & clock for 4017 or 4022.
On 5th count, invert & connect to first 555 reset.
 

hp1729

Joined Nov 23, 2015
2,304
I have a question about 555. I am trying to create (circuit diagram) a 5 minute count-down which is supposed to make a noise (buzzer) EVERY minute. So when the timer reaches 4 minutes it will make a noise and it reaches 3 minutes it will make a noise.

I have tried different thing circuits I found on the web but none of them really do what I need. Can someone link me a page that could possible help me with this?
Okay, here's a first draft for you. It depends on 60 Hz line for timing, but that can be modified. Some parts could not be specified yet.
 

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