Maybe add a low resistance and look at the collapsing voltage across it (an= d hence the coil current) in addition to the voltage across this should show when the magnetic circuit opens and give you some confidence that the surge is or is not present.=20 With your application the soft release on a fet will be unlikely to have reliable timing across parts due to manufacturing tolerances. Be cautious o= n the breaking of the contacts and look at what happens at the moment of separation with the load you will quite likely have a substantially longer arcing time particularly if switching DC S -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Justin Richards Sent: 01 January 2017 06:38 To: Microcontroller discussion list - Public. Subject: Re: [EE]: snubber protection diodes for inductive loads. Are they always required I have been trying to measure and capture the inductive spike without success. It is clearly evident when collapsing the coil directly and measure about 108V spike. when driven via the BS170 n-mos produces about 60v spike. I am guessing th= e body diode is clipping this. However, when the Gate is connected via a cap to ground, there is no measurable spike. Perhaps I need to devise a better test. Any ideas? On 1 January 2017 at 12:35, Justin Richards wrote: > That one second seems to cause so much grief. > > On 1 January 2017 at 08:03, John Gardner wrote: > >> Very nice, Jean-Paul. IIRC, the savants are adding 1 second >> >> to the length of this year to correct for various perturbations? >> >> >> ... >> >> >> >> On 12/31/16, Jean-Paul Louis wrote: >> > David, the beginning of the year is fairly arbitrary. What needs to=20 >> > be >> right >> > is the duration of the year, so there is no shift. >> > Earlier calendar were not exact in term of length of the year so a=20 >> > shift happened. >> > >> > Out of curiosity, why would you start the year at the winter solstice? >> It is >> > just another point on the elliptical orbit of the Earth, and not a=20 >> > significant point at that because of the orbit of the Earth, the=20 >> > tilt >> of the >> > Earth axis, and the other variations makes it almost impossible for=20 >> > the equinox to be constant either. >> > >> > Just $0.01, >> > Jean-Paul >> > N1JPL >> > >> > >> >> On Dec 31, 2016, at 7:35 AM, David C Brown wrote= : >> >> >> >> Never could get my head round the antipodean calendar.. Seems=20 >> >> just >> plain >> >> wrong to start the year in mid-summer. Even in the North we are >> several >> >> days wrong since it is self evident that the year begins at the=20 >> >> Winter Solstice >> >> >> >> __________________________________________ >> >> David C Brown >> >> 43 Bings Road >> >> Whaley Bridge >> >> High Peak Phone: 01663 733236 >> >> Derbyshire eMail: dcb.home@gmail.com >> >> SK23 7ND web: www.bings-knowle.co.uk/dcb >> >> >> >> >> >> >> >> >> >> *Sent from my etch-a-sketch* >> >> >> >> On 31 December 2016 at 10:32, RussellMc wrote: >> >> >> >>> I was going to say the same as Richard did re relay dropout. >> >>> I have never had the occasion to check the following in practice=20 >> >>> - >> it's >> >>> "out of my head". >> >>> >> >>> When the spring tension attempting to cause the relay to=20 >> >>> de-operate >> can >> >>> can >> >>> no longer be resisted by the attraction generated by the magnetic >> field >> >>> the >> >>> armature starts to move away from the pole face and the=20 >> >>> attraction >> force >> >>> almost instantly falls substantially with even a small airgap and=20 >> >>> the armature is pulled away with very little resistance, so=20 >> >>> usually quite rapidly. The change in inductance will depend on=20 >> >>> aspects of the relay design but I'd expect it could be substantial. >> >>> >> >>> The resultant inductive 'kick' is interesting to consider. ...=20 >> >>> deleted ... >> >>> I'm off shortly to take pictures of the midnight end/start of=20 >> >>> year fireworks. >> >>> Left as an exercise for the student ... >> >>> >> >>> I'd be liable to (1) check what happens (2) fit some form of >> suppression >> >>> regardless. >> >>> >> >>> >> >>> Russell >> >>> 31 December 2016, 23:30 >> >>> At the dawn of the day, edge of the empire, 1st to see=20 >> >>> the light ... >> >>> >> >>> >> >>> >> >>> >> >>> >> >>> On 31 December 2016 at 21:13, Justin Richards=20 >> >>> >> >>> wrote: >> >>> >> >>>> I have a working circuit that delays the off time of a relay. >> >>>> >> >>>> It simply has a 10uF in parallel with 3.3M ohm that is tied=20 >> >>>> between >> the >> >>>> Gate and Source of a BS170. The cap keeps the Gate voltage high=20 >> >>>> and >> >>> slowly >> >>>> discharges. >> >>>> >> >>>> In the original design I had a protection diode across the relay >> coil. >> >>>> >> >>>> But I need to make changes and space is limited and was thinking=20 >> >>>> the >> >>> diode >> >>>> can go. >> >>>> >> >>>> The rationale is that the coil never suddenly turns off so no >> inductive >> >>>> spike. The current gradually decays as the cap discharges over=20 >> >>>> a 1.5 min period. >> >>>> >> >>>> The data sheet also shows a body diode for the BS170. >> >>>> >> >>>> So what say ye, is there any argument for keeping the diode in=20 >> >>>> this case. >> >>>> >> >>>> Cheers Justin >> >>>> -- >> >>>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 >> >>>> View/change your membership options at=20 >> >>>> http://mailman.mit.edu/mailman/listinfo/piclist >> >>>> >> >>> -- >> >>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 >> >>> View/change your membership options at=20 >> >>> http://mailman.mit.edu/mailman/listinfo/piclist >> >>> >> >> -- >> >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 >> >> View/change your membership options at=20 >> >> http://mailman.mit.edu/mailman/listinfo/piclist >> > >> > Just my $0.02, >> > >> > Jean-Paul >> > N1JPL >> > >> > >> > >> > >> > -- >> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 >> > View/change your membership options at=20 >> > http://mailman.mit.edu/mailman/listinfo/piclist >> > >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 >> View/change your membership options at=20 >> http://mailman.mit.edu/mailman/listinfo/piclist >> > > -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .