> Conclusion for me: the quick FET produces the biggest spike, =

> independent from the diode. The voltage runs for nearly 1 =B5s =

> up to 160 Volts, measured with an good old analog Tektronix =

> 300 MHz scope. The best diode for suppression was a BYV2100, =

> a Schottky soft recovery diode (a little bit expensive as a =

> diode for a relay), the second best a 1N4148. At this diode =

> the spike was nearly 80 Volts high, so with an other relay =

> maybe the diode will come in trouble... (80V / 200 Ohm =3D 0,4 A !). =


I think you should not calculate like that: the voltage can rise only
because there is no current (the inductance tries to maintain the
current, and rises the voltage as needed)! And the 1N4148 I saw was
actually rated for 1A for short pulses.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu
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