| Author | Message | ||
     Anonymous |
Ok, what I need to do is a demonstration of a cristal radio to all my class. I have some questions : Can I remove the bottle, or is it essential for my radio ? Do my magnet wire needs to be very long (is 10 feets ok ?) Please answer by posting me a mail. | ||
| Simon Quellen Field (sfield) New member Username: sfield Post Number: 100 Registered: 12-2004 |
Of course I can't post mail to anonymous posters. The bottle keeps the wire in place. It is not necessary if you have another way to keep the wire in place. You need 50 to 60 turns of wire on a 2 to 3 inch form. The circumference of a 2 inch form is pi times 2 inches, or about 6 inches. Multiply by 50 turns and you get 300 inches, or 25 feet for the minimum. For 60 turns on a 3 inch form you get 60 times 3 times pi, or about 47 feet. I would get 50 feet of wire if I were you. | ||
| Anonymous |
Thank you ! | ||
| tanmoy choudhury (Unregistered Guest) Unregistered guest Posted From: 61.2.11.162 |
how to build a piezoelectric headphone from scratch? i can't find them locally. | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 761 Registered: 12-2004 |
We ship ours all over the world. But if you want to make your own, that can be a fun project. A sensitive (non-piezoelectric) earphone can be made by winding a few thousand turns of wire onto a rod magnet, and placing a thin steel diaphragm very close to the magnet. A piezoelectric earphone can be made by growing a Rochelle's Salt crystal, then grinding it carefully along the proper crystal axis, coating the edges with a conductor such as silver or our liquid metal alloy (or even pure gallium), and attaching wire leads and a diaphragm to the crystal. Commercial piezoelectric earphones such as those in our catalog are made by coating a brass diaphragm with a piezoelectric ceramic such as lead-zirconate-titanate, firing the ceramic, and orienting the piezoelectric polarity in a high voltage electric field. | ||
| chris martin (Chris) New member Username: Chris Post Number: 1 Registered: 9-2006 |
can some one tell me how it worksssssssssss | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 1472 Registered: 12-2004 |
I already did. "http://sci-toys.com/scitoys/scitoys/radio/homemade_radio.html" "http://sci-toys.com/scitoys/scitoys/radio/am_transmitter.html" But read the whole radio chapter -- there are important parts in places you might not expect. | ||
| jonlin (Unregistered Guest) Unregistered guest Posted From: 76.212.65.120 |
I purchased a Simple Crystal Radio Kit for my grandson's scienc fair. But it did not have instructions with it on how to assemble it. Can you help? | ||
| Michael (Michaelt) Senior Member Username: Michaelt Post Number: 146 Registered: 12-2005 |
If you have a printer, you can just go to http://sci-toys.com/scitoys/scitoys/radio/ten_minute_radio.html and print it. | ||
| paulo melendez (Paul0) Junior Member Username: Paul0 Post Number: 4 Registered: 9-2007 |
what does "grinding it carefully along the proper crystal axis" mean? found a 2 sites: http://rimstar.org/materials/piezo/rochelle1.htm http://www.seawhy.com/xlroch.html | ||
| Simon Quellen Field (Sfield) Senior Member Username: Sfield Post Number: 1787 Registered: 12-2004 |
See "http://www.ieee-uffc.org/freqcontrol/quartz/vig/vigqrtz.htm". | ||
| paulo melendez (Paul0) Junior Member Username: Paul0 Post Number: 5 Registered: 9-2007 |
thanks alot for the fast response! | ||
| Jane Doe (Unregistered Guest) Unregistered guest Posted From: 71.198.222.189 |
when you say wire is there any specific kind we should use? | ||
| Theresa Simmons (Theresa) Advanced Member Username: Theresa Post Number: 82 Registered: 1-2008 |
Generally, electromagnets are wound with magnet wire. That's why it is called magnet wire. Magnet wire is simply copper wire that has a thin coating of enamel on it as an insulator. The thin coating allows the wire to be wound more tightly than it could be with thicker insulation, allowing for a more compact electromagnet. | ||
| Jane Doe (Unregistered Guest) Unregistered guest Posted From: 71.198.222.189 |
if you want to use the homemade non piezoelectric earphone then how do you listen to it do you put the diaphram in your ear or....? | ||
| Theresa Simmons (Theresa) Advanced Member Username: Theresa Post Number: 99 Registered: 1-2008 |
Old fashioned high impedance headphones were usually worn over the ears, like earmuffs. That has the advantage of eliminating extraneous room noise. |
