Will this circuit work?

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gary350

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When the LED flashes will the buzzer buzz. I am only interested is a circuit where the buzzer buzzes about 1 time every second. I have not bought buzzers yet so I can't build a circuit to see if it works. Data on buzzer says nothing about DC or AC. Do data on buzzer volume either. Buzzer is probably about what is in a microwave oven.
 
You do not show the important polarity of the LED and "buzzer".
You do not show the important datasheets for the LED and the "buzzer" so that we will know the RANGE of LED voltages (nobody makes a 3.4V LED) and and if the "buzzer" is electro-mechanical or is a piezo beeper with a built-in oscillator.
The battery will be 3V only when it is brand new, then the circuit will soon stop working.
 

Online info says, Blue LED is 3.4v, 30ma

Online info says, buzzer is 3 to 5v, 25ma

2 brand new D batteries in series are 3.2v 8a

I have no part number, no name for buzzer, google is probably generic info. Google search for Buzzer data sheet shows nothing. I need a part number? Probably need a buzzer name too?

Here is very importing polarity drawing.

Can the flashing LED turn the buzzer ON?


 
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There are different types of buzzers. Some have built in drive electronics such that it will buzz as long as voltage is applied. Others don't have the electronics, so the drive electronics would have to be provided by the designer. The datasheet would specify the type.
 
The battery voltage is way too low. Use some arithmetic to see what the minimum battery voltage has to be. Hint: 3 V is not enough.

ak
 
I would suggest the following parts, available from Tayda Electronics.

Start with a red or orange flashing LED - Vf is ~ 2 volts, 20mA max. Flash rate is 1.5Hz.

This piezo beeper works from as little as 1.5 volts, 10 mA max.

You may need to use three Dollar Store batteries....you're still a bit short with 2 batteries.

I'm not sure if flashing LEDs are internally current limited, so a series resistor may be needed.

 
Gary, the Meanwell "buzzer" sales sheet says their buzzers are "active that beeps" or are "ready made that beeps". It is Chinglish and is meaningless.
If you use an electro-mechanical buzzer or a name-brand piezo beeper that has an internal oscillator then it will not get any voltage from a 3V battery in series with an LED because the battery voltage is too low.

A red or orange LED can be used as a warning. Therefore some are made to be flashing. A blue LED is never used as a warning therefor none are made to be flashing.

Depending on the type of buzzer or beeper, the LED will need a series or parallel current-limiting resistor.
 
I don't buy cheap junk ($0.03 for an LED) from a "seller" on ebay, AliExpress or Amazon.
 
That doesn't change the FACT that your declaration is wrong.

audioguru said:
A blue LED is never used as a warning therefor none are made to be flashing
Click to expand...

Also, for the record, I have purchased many parts from Tayda Electronics. All as described and high quality. Except for one order of terminal blocks where their definition of "vertical" vs "horizontal" didn't match mine, and the promptly sent the correct parts.

Yeah, I suppose Chinese sellers won't take a check (cheque?) to purchase parts.
 
Speaking of warnings, our oven timer makes one small beep when the timer goes off. When the microwave is done, it beeps every 30 seconds until you tend to it.

When the microwave beeps incessantly, the only danger is your food gets cold. If you miss the gentle beep of the oven, your next reminder may be smoke rolling out of the kitchen. Makes no sense.
 
Today I found what appears to be 2 types of buzzers from junk microwave oven circuits boards. I used a red auto flasher LED it flashes 60 times in 1 minute. I used a 470 ohm resistor in series with the LED. I also have a tiny speaker. 3 volts makes the speaker click click click each time I apply 3v. The larger buzzer in the center of photo makes clicking sounds. Buzzer on the right no sound.

Next I soldered the resistor & LED to each, speaker & both buzzers. Speaker the red LED flashes but speaker makes no sound on 3v.

Both buzzers make no sound and LED does not flash.

My idea to use the LED as an automatic switch to make the buzzers beep, does not work. If I buy a new piezo buzzer LED won't make it beep either.

I tried 3v 6v 12vdc on both buzzers with no resistor & no LED, no sound.

3v on LED flashes connected to the tiny speaker but no sound from the speaker.



 
Geez. Those are speakers. Did you expect the magical tone fairy to show up?

Who knows what voltage your random junk maybe piezo beeper works at?

The LEDs and beeper I pictured above were selected for specific characteristics. Sorry you won't find them at the Dollar Store or in a junk microwave.
 
3.4V LEDs are nominal Voltage @ 30 mA for both blue and white 5mm and using incremental Rs=16 ohms (typ.)

I expect at 5mA Vf= 3.4V - 25mA*16 ohm = 3.0V but it will drop quickly to near 0 brightness with battery voltage @ 2.5V

You would not put two different impedance devices in series and expect them to share battery voltage in half, thus you might choose to use them in parallel with a battery that still works at low voltage.

Buzzers come in many types and current is generally linear with voltage.
  1. Internal oscillator, piezo
  2. External oscillator, piezo
  3. Magnetic (electro-mechanical), internal oscillator.
LEDs with built-in flasher drivers (rare)
LEDs without flashers (common)

They are not all the same loudness and magnetic tend to be lower pitch.
The best solution is to choose a common flash rate for both and one can alternate the current between driving the LED on and then the Buzzer On to conserve power using a CMOS astable oscillator at any frequency in the 1 Hz range easily with 10 Meg and 68 nF.

This may not meet your simplicity requirements but is not hard to do with a piezo buzzer and an LED.

They do make vehicle backup flashing buzzers but these use several parts and naturally cost a lot more.
 
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The piezo in the middle is a piezo transducer (speaker) that does not conduct DC. The piezo on the right side probably has an oscillator circuit inside it which conducts DC and causes the piezo to beeeeep.
 
audioguru said:
The piezo in the middle is a piezo transducer (speaker) that does not conduct DC. The piezo on the right side probably has an oscillator circuit inside it which conducts DC and causes the piezo to beeeeep.
Click to expand...

The middle one that you call a transducer will make click click click sounds if I keep swapping battery wires +-+-+-+-+-+-+-. If I give the transducer +++++++++++ or ------------ it only clicks 1 time. This device needs AC to work. It clicks on 3vc and clicks louder on 12vdv. 3000KHz will make this device buzz.

The pieco on the right makes no sound 3v or 12v on DC or AC.

I asked the wrong question on this thread. I should have asked. How can I make a BEEP sound 1 times per second with minimum number of parts?

It is very easy to flash an NE2 neon with 1 resistor & 1 capacitor at 55VDC. With AC add 1 diode to the circuit. DC won't work in the transducer.

555 circuit will work, Mosfet osc circuit will work. But I want a very simple easy to build circuit very few parts if possible.

Anyone have suggestions for very simple 1 beep per second buzzer circuit?
 
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That is type 2 with the external oscillator. (constant or sweeping or beeping tone) Your choice. its external.
 
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