User:Epcole/enes100/Sound Powered Phone

Link to project EPC team page.

Give instructor top 3 project choice list
My top three projects were Power Projects, Corn Starch, and Infared.

Write problem statement
Make a sound powered telephone system

Assign Task1
Test how speakers can transmit sound

Compare actual work done to Task1
Recorded electrical signals created by speaker when diaphragm vibrates.

Week1 Narrative
Speakers and microphones convert sound vibrations into small electrical signals. To better understand this, I took a speaker and connected it to a National Instruments Data acquisition board. The electrical signal is generated when the speaker's coil moves inside the magnetic field of the permanent magnet. It creates sound when the coil is magnetized by electrical current - this attracts it to the permanent magnet, which causes the diaphragm to move. For this experiment, I basically used the speaker as a microphone and recorded the electrical signal created when the coil passes through the magnetic field. The signals were quite small, around 3mV peak.

Assign Task2
Learn about the history of the microphone and also the construction of sound powered telephone elements

Compare actual work done to Task2
Studied the construction of Sound Powered Telephone Elements

Week2 Narrative
I found out that unlike the speaker, the element of the sound powered phone has its coil attached to the end of a drive rod. Although there are different constructions, the basic idea is similar. the speaker has its coil attached directly to the diaphragm and it moves back and forth along one plane. I think attaching the coil on a balanced armature at the end of the drive rod allows the coil to move and vibrate freely. The coil is also balanced between 2 magnets. A drawing of this can be found here. I also did some searches for parts but haven't yet turned up anything. I would like to find an old unit or a part of it that I can take apart and get a better understanding of the elements inside.

Week2 Peer Review
Go to each team mates weekly summary wiki page. Read their activities and narrative. Then go the associated discussion page. Say something positive on this page. Try some constructive criticism. Add your name and 1sfoerster 13:32, 28 August 2011 (UTC) to create a time and date stamp. Create a new category if another team mate has already commented here.

Assign Task3
Search for sound powered telephone parts.

Compare actual work done to Task3
Spent the week trying to find parts from sound powered phones

Week3 Narrative
I did some searches for any antique electronics dealers in MD. Found a few but no one carried sound powered phone parts. I visited a flea market also and didn't have any luck. I did come across the NAVSEA website and found some information on the Inactive Ships Program. Its a program which allows the Navy to donate "obsolete" shipboard parts from scrapped ships to nonprofit organizations for educational purposes. Hoping there is one of those in the area that I can visit. There is also the DLA where the DOD auctions off some scrap parts to the general public. No sound powered parts on there at this time. Right now it looks like building a unit from the ground up might be a good way to better understand how they work. Thankfully, crystalradio.net has very detailed pictures of what the inside of an element looks like and has pictures of all its parts. That seems like a good place to start.

Week3 Peer Review
Go to each team mates weekly summary wiki page. Read their activities and narrative. Then go the associated discussion page. Say something positive on this page. Try some constructive criticism. Add your name and 1sfoerster 13:33, 28 August 2011 (UTC) to create a time and date stamp. Create a new category if another team mate has already commented here.

Assign Task4
Find individual parts and start planning on building a sound powered element from scratch.

Compare actual work done to Task4
Continued Search for Sound Powered Phone parts. Also began designing a prototype microphone unit.

Week4 Narrative
I haven't been able to find any sound powered phone parts yet, and the next Hamfest doesn't happen till January, so I started to move ahead with trying to build a sound powered system from the ground up. The first part is the microphone. It would be made from PVC since it is easier to cut and machine. Since the diaphragm would be made from latex, which I believe could be highly sensitive, we could end up with unwanted vibrations. To prevent this, there will be a dome over the diaphragm, which would be lined with a foam sheet to dampen vibrations in the casing from the sound waves. The entire casing might need to be lined with this if needed but for now, the dome will be the only part. In my research, I saw that a lot of microphones using diaphragms use two separate magnets, and the sound powered units on crystalradio.net also used two, so our mic would have the same. As of right now, I'm going to try to buy a coil but there is the possibility of building one if I can't find a suitable coil.

Week4 Peer Review
Go to each team mates weekly summary wiki page. Read their activities and narrative. Then go the associated discussion page. Say something positive on this page. Try some constructive criticism. Add your name and 1sfoerster 13:33, 28 August 2011 (UTC) to create a time and date stamp. Create a new category if another team mate has already commented here.

Complete Project Page
Follow the "project done" format.

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