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Topic: Buzzer Circuit (Read 3 times) previous topic - next topic

0

Hi
I would like to build a simple buzzer circuit which beeps for some 5sec then die off when AC power comes on. I know circuit is kinda simple but i cant seem to figure out  :( here is wat  I came up with...
AC to DC rectification (say 6v)
then a capacitor in series with resistor in series with a peizo buzzer...
like capacitor take time to charge till that time peizo buzzer is on after that once capacitor charges fully to max voltage peizo dies off...
I am i doing this the right way? or is there a better way to do it...
Plz do help out. I want to minimise the component count for this.
I keep feeling its such a simple circuit but I just cant figure out how to....  :'(

robtillaart

With an Arduino one could make one outputpin HIGH for five seconds in setup() when you want a nice "die off"consider digitalWrite(). see http://arduino.cc/en/Tutorial/AnalogInOutSerial, to get started.
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

0

It not power failure circuit. just the opposite. the buzzer should sound say for 5sec then die off. just to let me know that AC power is back.
With Arduino I can simply do this. but come on for such an easy task I don't think I need to use Arduino.
Any idea if the circuit i explained will work? My house is currently under renovation so I cant actually practically work on this for a week. Thats why I cant implement this currently and see if it works.  :(

CrossRoads

#3
Nov 02, 2010, 02:55 am Last Edit: Nov 02, 2010, 03:03 am by CrossRoads Reason: 1
So really want the AC going thru a relay that is Normally closed, and have some of that same AC be rectified into a low level DC (say by having the same AC drive a cheap wallwart as a 5V/12V source) , and have wallwart DC output go thru a current limit resistor to charge up a cap and eventually drive the relay into the open state to turn off the AC to your alarm bell.
System resets on power loss.

Shouldn't be that hard.

alarm bell:
http://www.signalguys.com/p/1005.html
(or just a cheap radio turned up really loud!)
wallwart power supply to drive relay (or as needed for the relay you pick)
http://www.mpja.com/prodinfo.asp?number=15178+PD
resistor & capacitor from your favorite supplier such that 1/2PiRC = 5 seconds (or something like that, maybe need a square root of 2 or something in there too, I'm a digital guy, go google it - big cap, small R)
relay:
http://www.mpja.com/prodinfo.asp?number=18255+RL
(is it just me, or is turn-on current/voltage not shown on the data sheet?)

Okay, this one is simple to follow
http://www.mpja.com/prodinfo.asp?number=18474+RL
5V across coils, 120V across the relay itself, good 1A (for that 125W radio, good & loud!)

Don't forget another R in parallel with cap to ground to make sure it bleeds off on a timely manner.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

0

#4
Nov 04, 2010, 03:11 am Last Edit: Nov 04, 2010, 03:15 am by dev_000 Reason: 1
This circuit will work? Its Buzzer which works at around 4V.
http://www.mediafire.com/i/?3gb6so3p8ck90pr
Shouldn't I add something to discharge the cap???

CrossRoads

I don't think so.  Even if the polarized cap you show wasn't damaged by being charged backwards, as I understood your original intent once the power came up & stayed up the cap would charge & stay charged so the buzzer would not stop until power went away.

You really want something that becomes turned off once the capacitor charges up, correct?
That's why I indicated the relay: power source thru Normally closed contacts to your +buzzer, -buzzer to ground.  
To control the relay: +6V to series resistor to +cap and to relay control. -cap to ground. bleed down resistor in parallel with the cap, value 10X of the series cap.
If it wasn't so late I'd draw a schematic & post it.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

0

Quote
You really want something that becomes turned off once the capacitor charges up, correct?

Yes, I would.
I really wouldn't like to have DC Source like a battery powering the buzzer. since its merely for the few seconds. wouldnt charging up a capacitor do?
I would really appreciate if you could draw up the schematic for the circuit you mentioned when you get time to do it.
Thanks in advance. :)
Seems like my simple circuit keeps growing bigger :-/

CrossRoads

Here's what I was thinking
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

0

@above
This should do the trick... Thanx a lot for the schematic :)

CrossRoads

Let us know  how it works out when you're done. Rbleed should be 10x Rdelay, I think I said 10X of the series cap earlier, typo on my part.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

0

Sure will work on it in a couple of days time :)

0

Yup it works... thanx for the circuit  :)

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