FANS, 5V LED ( was Re: Gecko current set resistor

Hi Alan,

you mean we're not supposed to re-invent the wheel every 6 months ?

: )

or is it to learn the mistakes of others, because you'll never live
long enough to make them all yourself ?

Dave, off on a quest to search the archives......

--- In CAD_CAM_EDM_DRO@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> Hi Dave, Listies,
>
> Read the previous thread (6 mo. ago?) on using a 12 or 24V DC fan
(and
> appropriate series resistor) to discharge cap and indicate charge
> remaining. You want a fan anyway!
>
> My collection of old PC power supply fans are typically 170 - 250
ma. A
> small resistor drops the need voltage from a 37 or 74v power
supply.
> IDENTICAL fans can be used in series.
>
> Another good way as Mariss published (see files) is to use a relay
to
> switch in a BIG bleeder resistor when the AC power is shut off. I'm
> happy with my fans!
>
> HTH
>
> Alan KM6VV
>
> turbulatordude wrote:
> >
> > Modern LED's are designed to use the 20mA and 5V as the basis for
> > determining resistors.
> >
> > There are some different styles like ones with internal resistors
and
> > ones with much lower power. The Garden variety is 5v-20mA
> >
> > I assume you are referring to the 1.7 volt drop across the LED so
> > I=5/R
> > but 5-1.7=3.3 volts for power
> > so I=3.3/R or 20mA=3.3/R
> > In many circuits you worry abourt wasting power, but my premise is
> > that at 1 amp, you are not worried about an 0.02 drain.
> >
> > You can power one with 40mA or lots more if you pulse the voltage,
> > makes it REALLY bright. if you don't get the pulse correct, it
makes
> > it's life REALLY short. The reasoning is that amps will heat the
> > LED if left on too long. and if the pulses are faster than your
eye
> > can seperate the pulses it will appear REALLY bright. and with
> > cooling between pulses, you do not risk the LED by over heating.
> >
> > And you are correct that 5v-20mA will yield a bright light. One
> > question is how big is that Cap and how long will it take to
bleed it
> > down ? and how bright will the LED be when there is still enough
> > charge to make you jump ?
> >
> > An LED will light quite nicely at lower voltages, so as the cap
> > discharges you will see a dimming as the voltage reduces. At some
> > point you will need to be in a very dark room to see the faint
glow.
> >
> > An LED should work up to about 40mA, but any spikes will soon
destroy
> > it. Also, you should have a faint glow at about 1mA. but you do
> > need about 1.7 volts to light it (1.9 for orange)
> >
> > At what voltage will your cap still shock you ?
> >
> > if you light at 20mA at 80 volts, your LED will glow dim down to
very
> > low voltages and will blead faster than a higher resistor.
> >
> > My use is not to just indicate, but to blead down the cap and read
> > voltages all the way to the almost safe level.
> >
> > besides it LOOKs like your machine has a lot of power when it is
> > glowing brightly. power ummmm......
> >
> > Dave
> >
> > --- In CAD_CAM_EDM_DRO@y..., JanRwl@A... wrote:
> > > In a message dated 21-May-02 12:11:17 Central Daylight Time,
> > > davemucha@j... writes:
> > >
> > >
> > > > Figure 20mA for the current and 5V for the LED
> > > >
> > > >
> > > >
> > >
> > > 5 VDC is WAY too much for LED's (except those special ones with
VR
> > > "on-chip")!!!
> > >
> > > 20 mA is BRIGHT for a T1-3/4. "Modern" LED's work fine on 10
or 15
> > mA!!!!!
> > >
> > >
> > > [Non-text portions of this message have been removed]
> >
> > Addresses:
> > FAQ: http://www.ktmarketing.com/faq.html
> > FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> >
> > OFF Topic POSTS: General Machining
> > If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach
it if you have trouble.
> > http://www.metalworking.com/news_servers.html
> >
> > http://groups.yahoo.com/group/jobshophomeshop I consider this
as a sister site to the CCED group, as many of the same members are
there, for OT subjects, that are not allowed on the CCED list.
> >
> > Post messages: CAD_CAM_EDM_DRO@y...
> > Subscribe: CAD_CAM_EDM_DRO-subscribe@y...
> > Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@y...
> > List owner: CAD_CAM_EDM_DRO-owner@y..., wanliker@a...
> > Moderator: jmelson@a... timg@k... [Moderator]
> > URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> > bill,
> > List Mom
> > List Owner
> >
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/