circuit to a beep with a switch is pressed

Thread Starter

jjarosz

Joined Oct 19, 2011
7
Hi Everyone,
I've looked through many of the threads on this and think a 555 might be the way to go, but haven't seen anything exactly like what I am looking for.

Basically, I'm looking for a circuit to make a short beep (maybe 1 second or a half second) when a switch is pressed each time. The switch I'm using is a push on-push off switch..so basically, I want a short beep when I turn the power on, and also short beep when I turn the power off..

I'm hoping that makes sense...any help is appreciated.

Joe
 

MrChips

Joined Oct 2, 2009
30,720
Ok, you have asked for three different things:

1. A short beep (half-second) when the power is turned on.
2. A short beep when a button is pressed.
3. A short beep when the power is turned off.

Is that correct?

(Keep in mind that for #3 the power is off).
 

Bernard

Joined Aug 7, 2008
5,784
Use two 555's, one for length, other for frequency. A 1/10 sec @ 1 kHz makes a nice chirp. Use a large cap to supply power for off chirp.
 
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Thread Starter

jjarosz

Joined Oct 19, 2011
7
Ok, you have asked for three different things:

1. A short beep (half-second) when the power is turned on.
2. A short beep when a button is pressed.
3. A short beep when the power is turned off.

Is that correct?

(Keep in mind that for #3 the power is off).
Probably my bad explaining it. The button is the on-off power, so when you push the button (which turns the power on) it makes a short beep. Then when you push the button again (which turns the power off) it makes a short beep. So essentially an audible tone when turning on or off via a switch. Sorry it wasn't clear earlier.

Joe
 

MrChips

Joined Oct 2, 2009
30,720
Joe, sorry, my mistake. I did not read your post carefully enough.

OK, it can be done. What kind of beeper do you plan on using?

It can be:

1) a typical 8-ohm loudspeaker
2) a piezo transducer
3) a 5V buzzer (maybe 4.5V)

How loud does the sound have to be?
 

Thread Starter

jjarosz

Joined Oct 19, 2011
7
Hi Ken, not sure why I didnt get a notify on your response, apologies for the delay..

I would use a discrete element. The draw is minimal. Essentially just used to switch on and off an LED which is used as a visual indicator.
 

KMoffett

Joined Dec 19, 2007
2,918
A discrete Piezo element will require additional components for an oscillator to drive it. How loud must the tone be? Can you use the DPST switch, or are you limited to an SPST?

Ken
 
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Hi,

This circuit has been helpful to me.

Note: this is not my own design, i received it from a very helpful member on the electronic-circuits-diagrams.com forum from member 'pebe'.
here is what he told me about the circuit:
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BEGIN QUOTE
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This circuit should do what you want. Only one of the four XOR gates of the CD4070 is used. Its logic is that if the two inputs are both high or low, then the output is low. But if one of the inputs changes state then the output will go high.

With SW open, points A, B, and C will all be high and the output will be low. C1 will be charged via R1.

When SW closes, A goes low. B will go low but C will stay high for 1/2 sec until C1 discharges. During that time the output will go high. As soon as C1 has discharged so B and C are both low, the pulse will end.

The same thing will happen as the switch is opened again.

Tie the 6 unused inputs to either 0V or V+ as convenient. Leave the 3 unused outputs unconnected.

Check on the data sheet for pin connections and chack the gate will supply the current you need.

Best of luck.
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END QUOTE
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What I found when hooking it up is to power it in parallel with your main circuit and a circuit that sounds whatever alert you want to use, *if* it triggers with a positive pulse. If you need a negative pulse, use the other circuit. if you need a longer or shorter pulse, play with the resistor/capacitor values to achieve the desired timing.

Regards,
David
 

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KMoffett

Joined Dec 19, 2007
2,918
Both circuits are dual-edge detectors. You will get a pulse out on both the positive-going and negative-going edges of the input. They do differentiate whether you get a high or low pulse at the output. However if jjarosz wants to use this with a power switch, it has to be powered from the battery all the time.

Ken
 

Thread Starter

jjarosz

Joined Oct 19, 2011
7
now that I read this, that point about being powered all the time concerns me a little. I'm assuming that means it will consume battery all the time while its waiting for the trigger, shortening battery life, am I correct on that?
 

KMoffett

Joined Dec 19, 2007
2,918
Yes. Depending on the capacitor leakage and the quiescent current for the IC it can be very small. But...it will be a continuous drain.

Ken
 
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