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Canary doorbell: How can I make it louder?

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gunsmoker

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I found this schematic floating around the net and built it for use as a doorbell. My wife and I like it very much but it would be nice if it were a tad louder.

**broken link removed**

I tried using an lm386 op amp on the output of this following a schematic provided in it's datasheet, also I tried using an identical transformer hooked up backwards to the existing transformer and directed the output from that into the op amp circuit but that didn't work either, I only got a long downward spiraling tone, but I honestly am not sure I had the transformer hooked up right because of the center tap on the primary winding: where should it go? I tried several configurations with the transformer as well as without. It seems the extra circuitry is throwing off the amount of time required to charge and discharge the capacitors. It finally occured to me that maybe what I'm dealing with here is not an ordinary signal like from an mp3 player but something else. Any help would be greatly appreciated as I am still an infantile electronics newbie and my wife and I have become quite attached to this cute little circuit, the grandchildren and the nephews and nieces love it too.
 
My 1st thought is to use a 4 ohm speaker rather than an 8 ohm.
 
Okay, I found a couple 3.2 ohm speakers, hooked one up and it sounded even weaker than before. Just to be sure I tried the other 3.2 ohm speaker and it sounded very weak, too.
I guess I can live with it the way it is, but it's not loud enough when I'm in the back of the house.
 
It was worth a try.
There are 2 other paths to go by then.
1: Attach an amplifier to the speaker output but this may be problematic with a source impedance of 8 ohms.
2: Modify the circuit so that a simple low power amplifier can be attached but again this may run into problems as the output transformer forms part of the resonant circuit.
I'm sure someone on here can shead more light on this. I'm curious about a solution myself now.
 
Yes, it was definitely worth a try, thank you very much, Zed. I have worked with this thing off and on for a while now, I'll give up on it then take it down weeks later and try something else, always wind up putting it back up to haunt and tease me.
 
The 1000 ohm winding has 250 ohms from the center-tap to the transistor driven with 9V. Therefore the peak current is only 9V/250 ohms= 36mA. The peak power is only 9V x 36ma= only 324mW. the transformer isn't perfect so the speaker gets about only 260mW. Peanuts power.

An LM386 gives an output of nearly 1W into an 8 ohm speaker with a square-wave input and a 9V supply. 1W sounds a little louder than 324mW. 3.24W will be twice as loud.

I would increase the supply voltage to the existing circuit until the transistor gets pretty warm. 24VDC would make it pretty loud.
 
Thanks, Audioguru. 24v makes it significantly louder, now all I have to do is build a little 24v power supply to hook up to it.
I had tried 12v a few months ago and it did not sound a bit louder, after reviewing the math I can see why -- it had only increased the power by 252mw. So I had abandoned ideas of increasing the voltage. I have learned much since then, and have a lot more to learn, that's part of the fun.
Thanks again, Audioguru and Zed.
 
You could get a real canary and connect up a solenoid so that it bangs its balls together when the doorbell rings.
 
if you don't want to get into too much trouble, you may as well hock the output to small 'made in china' speakers, that are fed from the mains, and have an integrated AMP..., then you can control the volume as you wish...
 
Why a canary for an annunciating task. You should be using either a Macaw or a Screech Owl.
 
I wound up using a power supply from an old Lexmark printer, it's 30v 400ma, in it's own little 3x3x1 inch box with the power cord removed and speaker wire in it's place run to a light switch box. I soldered a fuse inline with the hot wire inside the light switch box, the speaker wire is a lot less intrusive than the power cord would have been.
 
Does it just not work when connected up to the LM386 or is it just not loud enough?

You might need to add an 8:eek:hm: resistor to the output then the LM386 aplifier.

You could also try the TDA7052.
 
Hero999 said:
Does it just not work when connected up to the LM386 or is it just not loud enough?

You might need to add an 8:eek:hm: resistor to the output then the LM386 aplifier.

You could also try the TDA7052.

When connected to the lm386 it doesn't work properly, it just starts about mid range and tapers off and sort of hangs without the canary twitter. I tried it after connecting 30v also, same result. I might try with the 8 ohm resistor on the output, though. What effect might that have?
 
The circuit might be designed to only work when the speaker is connected and adding an 8:eek:hm: resistor will make it appear as though a speaker is connected.
 
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