Making a small Alert sound

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Ron Potashnik

Joined Dec 27, 2015
16
Hi everyone.
i want to make a small product the't when i charge it he will be quiet, and when i'm stop charging it he will make a strong alert sound for like 15 seconds. i want it to have a car electricity exit.
i think i suppose to use a capacitor , resistor and timer but i don't know how to make it like a small and nice product.
i need your help in what component's to buy, how to build the circuit and how to make it accessible for use.
 

Bernard

Joined Aug 7, 2008
5,396
A thought: Use a PNP transistor & a current sense resistor to trigger a 555 one shot which drives a piezo buzzer. Need more inf. on charging load.
 

hp1729

Joined Nov 23, 2015
2,304
Design 952 charge gone alarm.PNG

Just a starting point. Sonalert puts out about 3 KHz at about 90 db and only draws about 10 mA at 9 V.
As long as "charging" is present Q1 is held on. When "charging" goes away. Q1 turns off, Q2 turns on giving a pulse to the LM555. The LM555 gives a single pulse out for about 15 to 20 seconds, turning the Sonalert on.
How close is this to what you want?

Hi everyone.
i want to make a small product the't when i charge it he will be quiet, and when i'm stop charging it he will make a strong alert sound for like 15 seconds. i want it to have a car electricity exit.
i think i suppose to use a capacitor , resistor and timer but i don't know how to make it like a small and nice product.
i need your help in what component's to buy, how to build the circuit and how to make it accessible for use.
If you are provided a schematic could you build a circuit from that?
 
Last edited:

WBahn

Joined Mar 31, 2012
25,250
What kind of "small and nice product" are you talking about? How many of these are you hoping to make? Ten, or ten thousand?

What do you mean by "when I'm stop charging it"? Do you mean when it is removed from the power source, or do you mean when it has determined that it is fully charged?
 
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