Calculations, formulas and diagrams for calculating and estimating self inductance of various structures.
http://home.san.rr.com/bushnell/self_inductance.htm
second edition
http://home.germany.net/100-173822/d_logg2_engl.htm
detects when someone traverses the gate, ringing the bell in a very peculiar way.
http://www.nutchip.com/progetti/annunciatore_en.htm
http://w1.859.telia.com/~u85920178/use/filt2.htm
detect minute variations of a magnetic field, particularly the Earth magnetic field
http://www.geocities.com/CapeCanaveral/Lab/5185/circuit1.html#SENSITIVE
http://www.asel.udel.edu/robotics/sensory_fb/sensory_feedback.html
using 10 LEDs
http://www.uoguelph.ca/~antoon/gadgets/bfflash2.htm
with PIC microcontroller
http://www.imagesco.com/articles/picservo/02.html
an interface to convert pulses such as provided by R/C receiver to a dual PWM signal required by an H-bridge to drive a DC motor.
http://www.bobblick.com/techref/projects/sv2pwm/sv2pwm.html
Servo Pulse Generator.
http://www.uoguelph.ca/~antoon/gadgets/servo2.htm