Identify speaker - Page 1
Forum section: electronics / beginners

author: fixit7
author_rank: Regular Contributor
timestamp: May 25, 2019, 04:18:37 pm
content: 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

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 25, 2019, 06:45:20 pm
content: 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.

author: mikerj
author_rank: Super Contributor
timestamp: May 25, 2019, 06:54:50 pm
content: Quote from: PA0PBZ on May 25, 2019, 06:45:20 pmNot 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.

author: fixit7
author_rank: Regular Contributor
timestamp: May 25, 2019, 08:42:14 pm
content: Quote from: PA0PBZ on May 25, 2019, 06:45:20 pmWas not aware it was an AC speaker.

author: Zero999
author_rank: Super Contributor
timestamp: May 25, 2019, 10:14:39 pm
content: Quote from: fixit7 on May 25, 2019, 08:42:14 pmAll 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.

author: fixit7
author_rank: Regular Contributor
timestamp: May 26, 2019, 12:44:30 am
content: Quote from: Zero999 on May 25, 2019, 10:14:39 pmThanks.I have one of these. Does it run on AC?What is the 5Vp-p?Piezo TransducerElectrical Specifications:Rated Voltage: 5Vp-pRated Current: 2mA (max)Sound Output at 10cm: 85 dBAResonant Frequency: 2.04kHz

author: timelessbeing
author_rank: Frequent Contributor
timestamp: May 26, 2019, 02:09:56 am
content: Vp-p = Peak-to-Peak voltageAre you trying to make something, or just taking things to bits to see what they do?http://www.bcae1.com/audoutex.htmhttp://www.bcae1.com/speaker.htm

author: fixit7
author_rank: Regular Contributor
timestamp: May 26, 2019, 02:50:22 am
content: I made this circuit on a experimenters breadboard.After I knew it was working, I soldered the components to one of these.PCB Prototype Circuit Solder BREADBOARD - Discrete and DIPhttps://makezine.com/projects/laser-tripwire-alarm/I made some modifications by adding a piezo buzzer instead of a plain speaker.I also had to put a 3 inch piece of PVC pipe over the Cadmium PhotoCell to keep non-laser light from affecting the circuit.

author: timelessbeing
author_rank: Frequent Contributor
timestamp: May 26, 2019, 04:03:23 am
content: does it work?

author: Zero999
author_rank: Super Contributor
timestamp: May 26, 2019, 07:20:11 am
content: That circuit requires a buzzer to work. It will not work with plain speaker or piezo transducer which doesn't have an internal oscillator. It it works, then you're using a buzzer - well done!

author: fixit7
author_rank: Regular Contributor
timestamp: May 27, 2019, 02:29:45 am
content: Quote from: timelessbeing on May 26, 2019, 04:03:23 amYes, both the circuit and buzzer work.The diagram was from the author of the circuit.I am learning to use Geda to create my own circuit diagrams.I looked for a symbol for a piezo buzzer. The closest I found looked like a speaker with plus and minus terminals.It was quite a leaning experience going from the solderless breadboard to soldering the components in the final board.Learned a lot and it will take quite a bit of practice to get good.I will eventually need a temp controlled iron as my "Hakko knockoff" was overheating as the dial readings did not correspond to the actual tip temperature.AndyAndy