Help Door Knob Alarm

shteii01

Joined Feb 19, 2010
4,644
Since u r unable to formulate observations and requirements, I will offer some suggestions that might or might not work:
- reduce r1
- increase b1
- instead of buzzer use amplifier and attach louder sound device (buzze, speaker, whatever) to the amplifier.
 

ian field

Joined Oct 27, 2012
6,539
Hello everyone
I need some help on this circuit
Piezo in this circuit is not alarming loud enough
I tested it on Proteus
Can anyone help me
Many commercial products have a peaking inductor in parallel with the piezo sounder.

Step up autotransformers aren't exactly rare in CO alarms that need to be loud.
 

Thread Starter

Grizzly09

Joined Oct 24, 2017
11
Many commercial products have a peaking inductor in parallel with the piezo sounder.

Step up autotransformers aren't exactly rare in CO alarms that need to be loud.
Actually it's almost like a silent.And as you can see i should have used touch palette but i replaced it with a button.Clicking button doesnt make any noticeable change in sound.
Thanks for the reply
 

ian field

Joined Oct 27, 2012
6,539
Actually it's almost like a silent.And as you can see i should have used touch palette but i replaced it with a button.Clicking button doesnt make any noticeable change in sound.
Thanks for the reply
Piezos need a fair bit of voltage - they're also capacitive and resonant. you'd probably hear it if you drive it at the right frequency, but most commercial products have some form of peaking inductor.
 

Alec_t

Joined Sep 17, 2013
11,141
Clicking button doesnt make any noticeable change in sound.
I'm not surprised. The pull-up resistor R8 is probably effectively clamping the oscillator output to the positive rail, and pressing the button clamps the output to the negative rail. Both situations result in Q3 turning off and the sounder being actuated.
 

Thread Starter

Grizzly09

Joined Oct 24, 2017
11
I'm not surprised. The pull-up resistor R8 is probably effectively clamping the oscillator output to the positive rail, and pressing the button clamps the output to the negative rail. Both situations result in Q3 turning off and the sounder being actuated.
Any tips or answers will be very appreciated.
 
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