Reduce volume of AC buzzer

It might take a resistor rated for several watts to get what you want, and pots with that rating are rare and expensive. So it might be better to try a few values of fixed resistors and pick one to install, permanently.

Or you might use a series capacitor that is rated for plenty of AC voltage (say, 250 VAC) to drop the extra voltage without producing heat. Something between 0.1 uF and 1 uF might do it.

Cover the buzzer with something. The more you cover it, the weaker the sound will be.

If it was an electric bell, you could weaken the sound by damping the actual bell, or putting something between the hammer and the bell.

I'm not actually that familier with many buzzers to know what might be directly applied, assuming one can get at the works, but something similar is bound to work.

Michael

Duct tape.

John

:I've got an old Gralab darkroom timer with a buzzer that is, to my :taste, way too loud. Some Gralabs had a volume adjustment knob, this one :doesn't. I'd like to add one. : :The buzzer is labeled: : :U.S. Controls Corp :120V, 50-60Hz. 4W :Pat. Pend. Int. Duty :25%W/Max. Ontime :30 Sec.@65C. Max :10037-63 : :Googling part numbers turned up nothing useful, but I'm guessing that :it's a simple vibrating electomagnet type thingy that strikes the metal :plate attached to the bottom of the black box. : :Now, it seems that wiring a pot in series with buzzer should reduce :the voltage it sees, reducing the amplitude of the vibrations and thus :its volume. Or do I need something fancier? : :If a pot is sufficient, how to size? Is it as simple as Ohms Law would :imply? That is: 120V 4W -> 0.033 A and 3600 ohms, and thus a 5K or 10K :pot would provide plenty of adjustment? Or is such a buzzer likely to be :more sensitive to voltage, making a 5K pot too sensitive? : :Thanks, :Steve

Maybe you can get advice from the manufacturer.

How about a diode?

Best regards,

Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis

Is that safe, in an inductive load?

I've never done it , in spite of using caps for LV supplies. My concern is that I might form a series resonant circuit and get some reactive voltages much higher than I was planning on.

Just curious on what you think.

(snip)

I doubt it is a very high Q inductor, but, it is possible that there is a resonant capacitor value that would peak the voltage measurably above line voltage. That would make it louder, so I doubt the O.P. would use that value for long. But that possibility is the reason I said the cap should be rated at twice line voltage. No point in having the cap pop during a momentary test.

But as long as the capacitor value is considerably less than the resonant value (somewhere around 2 uF, I think), the cap will drop the voltage applied to the buzzer, even though the sum of the cap drop and the buzzer drop may add up to more than the line voltage. I.e. he might like the sound where the voltage across the buzzer is 3/4 of line voltage, and the voltage across the cap is also 3/4 of line voltage.

I am reluctant to advise that without knowing how the unit works. It my include a permanent magnet. Inductive loads and diodes often do not get along.

Duck tape is better. It keeps all your ducks in a row!!! ;-)

-- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85.

Michael A. Terrell Central Florida

Well, covering it doesn't do much, because, it turns out, quite a bit of the noise is from it being bolted against the case. Installing a bit of rubber padding between the two helped a lot. Whether or not it's enough, we'll see.

I've also e-mailed Gralab, as suggested, to see if they'll sell me the volume control part. If not, I guess I'll need to dig out my EE280 text book and figure out how big a capacitor I need.

BTW, I pulled apart the box, and, as I suspected, it's just a coil with a metal bar that strikes the base plate.

Thanks for the replies.

Steve

Put a couple of thicknesses of duct tape on the spot where it hits.

Good Luck! Rich

Unfortunately, the way the coil is mounted in the metal clip/base doesn't allow disassembly by the amount of force I'm willing to apply.

I could stick a bit of tape on the end of the center cylinder, I suppose, but it's not very big, and if it came unstuck it would probably jam things nicely.

The good news is that Gralab is going to send me a copy of the parts catalogue they use. Presumably I'll be able to order the volume control thingy.

Steve