[DIY] the accidental human conductor

Usually I would take a break from intense studying by doing some non technical related activity such as cooking, baking etc. But in the office environment, en-suit kitchen is consider a luxury and way out of my reach. Instead, I make little toys (electronics) /handicraft (mastering the art of folding roses) to kill off the gloomy mood from studying non stop.

I wanted to make a Amplitude Modulated Laser Transmitter for Audio. There are many examples (successful ones) plastered all over the Internet.It originates from here ...
http://www.freeinfosociety.com/site.php?postnum=2310

What you will need
1. 1x laser pointer S$1.9 from $2shop.
2. 4.5v battery
3. Audio output transformer (8ohm and 1k ohm impedance)S$1, S$3. This is the tricky one, i shall elaborate later.
4. LDR
5. Speaker, USB powered preferred over passive ones.

Connect them up accordingly. The schematics are available from the link above. From left the laser pointer, the battery pack, the audio output transformer and audio out from the laptop.

Now, hook up the receiver part. The USB powered speaker, LDR.

Now, the tricky part. The "audio output transformer" (branded by the shop with no rating) which was sold to me for $3 does not work. After measuring the impedance using a Digital Multi Meter, it only have 2ohm and 600ohm impedance, a far cry from what I need. The output from laser pointer is very very very weak. The LDR cannot pick up the light intensity. I made another trip down SLT and one of the shop owner sold me a $1  "audio output transformer" . Tough luck I may say, the impedance does not match. The output from the laser pointer still as weak. Hunt around the labs for some spares......no luck at all.

I guess there will be another round of parts hunting, AFTER I finish my exam.

During the 30minutes of playing with the above mentioned toy, i noticed something.

When I am holding the LDR+USB powered speaker's mini stereo jack on my RHS and the laser pointer + messy wires at my LHS. The speaker output some music even though I DID NOT  press the "on" button on the laser pointer. Which it should not be the case. When I DID press the "on" button, the music is cut off! For a moment, I thought it is a very strange phenomena that doesn't make sense. But...after 2 seconds... HAHA.....

The first correct answer to that "strange" phenomena and why I press on the button of the laser pointer the music is off, shall get 1x muesli bar from me. Leave your answer on my post as a comment~


Nonetheless, it is still COOL to be the human conductor by touching both the receiver end and the transceiver end to produce some sound without using a physical wire. TRY IT AT YOUR OWN RISK!!! IF you or any parts thereof Got FRIED, I shall bear no liability nor responsibility.

Below is a video of it, still can WOW some crowd if it is packaged in a magic show. E.g, asking an audience come up to the stage to touch an exposed end (eg the receiver side), while holding at the magician's hand. The magician shall strut his/her stuff with the physics behind it.


now... back to the books..........

[news] Top 500 super computers!!!!

link : http://news.bbc.co.uk/2/hi/technology/10187248.stm