Electronics > Beginners
Identify speaker
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fixit7:
This is from a cordless phone.

I think it is a speaker.

Phone uses 2.4 volt battery.

I was wondering if it would work in a 9 Vdc circuit?

https://www.dropbox.com/s/yy6rwm0vib91010/PhoneSpeaker.jpg?dl=0
PA0PBZ:
Yes it is a speaker, and the characteristics are printed on it. Since a speaker is driven with AC your question about 9V DC is irrelevant.
mikerj:

--- Quote from: PA0PBZ on May 25, 2019, 06:45:20 pm ---Yes it is a speaker, and the characteristics are printed on it. Since a speaker is driven with AC your question about 9V DC is irrelevant.

--- End quote ---

Not entirely irrelevant.  A 9v pk-pk signal across that 150ohm speaker would be around 68mw, more than double it's rated power.

A high impedance driver like that could be driven directly from the output of an op-amp.
fixit7:

--- Quote from: PA0PBZ on May 25, 2019, 06:45:20 pm ---Yes it is a speaker, and the characteristics are printed on it. Since a speaker is driven with AC your question about 9V DC is irrelevant.

--- End quote ---

Was not aware it was an AC speaker.

Zero999:

--- Quote from: fixit7 on May 25, 2019, 08:42:14 pm ---
--- Quote from: PA0PBZ on May 25, 2019, 06:45:20 pm ---Yes it is a speaker, and the characteristics are printed on it. Since a speaker is driven with AC your question about 9V DC is irrelevant.

--- End quote ---

Was not aware it was an AC speaker.

--- End quote ---
All speakers need to be driven from AC. The sound they produce mirrors the AC waveform. For example put in 1VAC at 1kHz and it will produce a 1kHz tone. There are limits of course the the upper and lower ends of the frequency response. This telephone speaker is probably only good for a narrow frequency range of 300Hz to 3kHz.

The only things which beep and work off DC are buzzers, basically a simple speaker with a built-in oscillator which converts the applied DC voltage to AC to drive the speaker. The oscillator in a buzzer can be either electronic (normally just a transistor with feedbacl) or electromechanical: basically a relay with a normal closed contact wired in series with the coil and the moving iron attached to a diaphragm to improve the coupling of the vibrations to the air.
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