[Printers] Blue LEDs from Radio Shack

[Seth David Schoen]

If you want to see tracking dots for yourself without buying an LED
flashlight or modifying a scanner, a cheap way is to go to Radio Shack
and buy two "5mm blue LED 3.7 volt 20 mA 2600 mcd" LEDs (Radio Shack
part 276-316).  You can then buy a 9V battery and twist together (or
clip together) one positive lead and one negative lead from the pair
of LEDs.  Then you can attach it to the battery and you're within the
rated voltage of the LEDs without a resistor (they say that they
accept a maximum forward voltage of 4.5 V).  I'm sure Bunnie can give
arguments for why one should use a resistor anyway, but this is close
to reasonable in terms of being unlikely to burn out the LEDs from
over-current right away.

This will cost you about $15.  You can hold the LEDs directly against
the 9V battery terminals even without a battery clip, if you want (or
you could splurge and buy a 9V battery clip).

-- 
Seth Schoen
Staff Technologist                                schoen at eff.org
Electronic Frontier Foundation                    http://www.eff.org/
454 Shotwell Street, San Francisco, CA  94110     1 415 436 9333 x107