Re: [[EE] Resistor power rating

Just be careful though, I have had "concrete block" wirewound resistors
smoke on me. I don't know exactly why but suspect it was something to do
with peak current at switch on.
The ones I refer to as "concrete block" are those in a 1" cross section
ceramic package with a cermet mixture on on side where the element gets
inserted.


On Tue, 9 Dec 2025 at 08:55, David C Brown <[email protected]> wrote:

> Thanks for that.   It seems that a 5w wirewound resistor wold easily meet
> my requirements
> __________________________________________
> David C Brown
> 43 Bings Road
> Whaley Bridge
> High Peak                           Phone: 01663 780582
> Derbyshire                eMail: [email protected]
> *SK23 7ND          web: www.bings-knowle.co.uk/dcb
> <http://www.jb.man.ac.uk/~dcb> *
>
>
>
> *Sent from my etch-a-sketch*
>
>
> On Mon, 8 Dec 2025 at 22:22, Clint Jay <[email protected]> wrote:
>
> > Vishay and Bourns both have info on their wesbites about selecting
> > resistors for pulse load applications:
> >
> >
> >
> https://www.vishay.com/docs/48516/_ms9702509-2401-vishaychecklistpulseload.pdf
> > https://www.bourns.com/products/resistors/pulse-power-resistors
> >
> > On Mon, 8 Dec 2025 at 19:32, Jason White <
> > [email protected]>
> > wrote:
> >
> > > vishay makes some nice pulse rated 2512's that have some graphs where
> you
> > > can look this up in
> > >
> > > On Mon, Dec 8, 2025 at 2:09 PM David VanHorn <[email protected]>
> > wrote:
> > >
> > > > Normally, resistor power ratings assume 100% duty cycle, so 1/0.016
> > would
> > > > be a first approximation, but the part may not be capable of
> > withstanding
> > > > that much pulsed power.
> > > > Unfortunately, the low duty cycle ratings are hard to find on most
> > > > resistors.
> > > >
> > > >
> > > > On Mon, Dec 8, 2025 at 11:37 AM David C Brown <[email protected]>
> > > wrote:
> > > >
> > > > > I am planning to use a 2R2 resistor to limit the current to a
> > solenoid
> > > to
> > > > > 6amps.
> > > > > Ohms law says that the power dissipation is about 80watts.
> > > > >
> > > > > But the duration of the current pulse is only 16mS.   Does that
> mean
> > > > that I
> > > > > can get away with a lower power rating and, if so, how much lower?
> > > > > __________________________________________
> > > > > David C Brown
> > > > > 43 Bings Road
> > > > > Whaley Bridge
> > > > > High Peak                           Phone: 01663 780582
> > > > > Derbyshire                eMail: [email protected]
> > > > > *SK23 7ND          web: www.bings-knowle.co.uk/dcb
> > > > > <http://www.jb.man.ac.uk/~dcb> *
> > > > >
> > > > >
> > > > >
> > > > > *Sent from my etch-a-sketch*
> > > > > --
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> > > --
> > > Jason White
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> > --
> > Clint. M0UAW IO83
> >
> > *No trees were harmed in the sending of this mail. However, a large
> number
> > of electrons were greatly inconvenienced.*
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