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timed beeper

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lisoff

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hey,
could someone plz point me in the right direction of making a circuit that beeps every minute or so or maybe even a random beep that can be connected to a 8 ohm speaker would be preferable if it can be run from a 3v button battery

Thanks in advance
--
Daniel
 
yea the thing is that i have never used a PIC and have no idea how to program one so that presents a problem could it be done with a 555 timer??? also do i need a audio generator or something???
 
lisoff said:
yea the thing is that i have never used a PIC and have no idea how to program one so that presents a problem could it be done with a 555 timer??? also do i need a audio generator or something???

You could do timed beeps with a number of 555's, but the timing won't be very accurate.
 
I don't usually draw out schematics, but here you go. I reccomend the use of an ICM7556 dual CMOS 555 chip and 4000 series NAND gates. The top oscillator generates an audio frequency beep, adjust C1 in it to alter the beep frequency (I guessed values). The bottom oscillator sets the delay between beeps, adjust C2 to alter this delay. The NAND gates U3C and U3D with R5+R6 form a schmitt trigger together, with the capacitor and 10k resistor before them forming a high pass filter. Alter the bleep length cap to adjust the bleep length. I haven't tested this or simulated it, but it should work; definatly try it on breadboard first and find values you like. I know this can be implemented with just two 555 and a discrete MOSFET, but adjusting it is much harder.
 

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the timeing isnt really an issue as long as it doesnt consume too much power and can generate a tone any ideas????

THANKS
--
Daniel
 
Well, my design should draw very little power so long as the CMOS 555 versions are used. However, if you want to drive an 8ohm speaker, that will use excessive power. A piezo transducer is what you want, it should be able to be driven directly from the logic gate output, or for more volume, use a discrete MOSFET follower.

3v is a bit difficult, it might work, but the battery voltage will drop over its life, and the operation will probably stop fairly quickly. 5v+ is more suitable.
 
Dr.EM said:
3v is a bit difficult, it might work, but the battery voltage will drop over its life, and the operation will probably stop fairly quickly. 5v+ is more suitable.
National's LMC555 is guaranteed to work with a supply as low as 1.5V.
74HCxx is guaranteed to work with a supply as low as 2.0V but the output current will be very low.
 
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