From: SFPhysics@aol.com
Date: Fri May 06 2005 - 02:16:45 PDT
From: SFPhysics@aol.com Message-ID: <45.27b387a1.2fac8ffd@aol.com> Date: Fri, 6 May 2005 05:16:45 EDT Subject: Remote Control Explorations
>>Does anyone have any ideas for how we can use old remote controls in our
classroom? These things keep piling up and I'm sure we can do something
educational and interesting with them.
>
>
Marti Andreski
De La Salle HS
<<
Greetings Marti:
I like to put a silicon solar cell attached to an amplifier to let students
hear that IR emitting remotes have different digital outputs for different
functions. You need to do this in a room without the normal 60 Hz lighting
turned on (which you will hear as a 120 Hz tone) and not too much sunlight. I
put the solar cell at the sealed end of a short cardboard tube with the inside
painted black then hold the remote on the open end. If you connect the cell
to an oscilloscope you can see the pulse train that is generated. A good
O-scope with memory function will let the students figure out the digital
sequence and they love to do this. The binary code can also be converted to base
10 with some interesting results. Some remotes will transmit the same code
over and over so a regular O-scope will be able to read the output. Generally
commands to raise or lower volume and change channels will be repeated.
The IR output will also let you test various materials for IR transmission
using the silicon solar cell and amplifier. Cellophane tape, mylar tape,
polypropylene film, mica, glass, clear plastics, gems, etc. can all be tested to
see if they will pass IR light. Most everything does but a few materials
that pass visible light will not pass the IR. The students can have fun trying
to find those that will not.
If you are good with a very small soldering iron you can put in a normal LED
that transmits in the visible range. This alone will show that there is an
energy output from the unit. The LED is polarity sensitive so make sure the
cathode goes to the correct connection. An old spinning strobe wheel can
show the pulses in many cases (the kind with the slits cut radially around the
periphery and spun my a motor with a speed control).
I had a friend who would aim an IR remote at his dog, not an old ultrasonic
unit, and the dog would come if he saw the beam. I could never figure out if
it was a trick or the dog's vision went into the IR region.
Best wishes to all on the list,
Al Sefl
Who always goes to the kitchen when the microwave light is on...
And salivates when he hears the microwave done bell...
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