-----Urspr=FCngliche Nachricht----- = Von: "Michael Rigby-Jones" An: "Microcontroller discussion list - Public." Gesendet: Montag, 06. Februar 2006 18:57 Betreff: RE: [EE] Transient Suppression - was Re: [ee] 3904 base resistor [rest snipped] > = > The 1N4148 is good for application up to many 10's (possibly 100's?) of M= Hz, is the rise time of the induced voltage really too fast? I guess that a= ll depends on the speed of the driver but the commonly used saturated bipol= ar device is comparatively slow to switch off. > = > Fairchilds 1N4148 is rated for 1 Amp forward current for 1 second at a Vf= of 1.5 volts. I've not done the calcs but this feels like it would be ade= quate for the majorty of small relay applications. Then again, I guess the= re may be an awfull lot of inferior devices being sold as 1N4148's that hav= e nothing like these specs. Still though a failure in this case could only= be attributed to an under rated component. I don't think that the problem is speed or current - the problem is the vol= tage. A 1N4148 is rated with 100 Volts and this could be less if you switch= off a relay. From my experiences a 1N4007 as a general purpose diode with = Vrrm =3D 1000V and much reserves in non repetitive current will do the job = without problems and cost nearly nothing. = Regards Enrico -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist