Geert Decorte wrote:
AFAIK (my technical college time is 20 years behind me now) You need to
feed a led with a current of aproximity 15 mA (should have to look a
datasheets for this). Depending on the color of the led the tension could
be in the neighbourhood of 1.2 V
So the value of R would be
R = (UHD - 1.2)/15 mA
This are a few standard rules out of the head
better values: http://www.kpsec.freeuk.com/components/led.htm
You have to be aware of the following: UHD is the tension measured without
charge (without led). The value of R can be a variable of the resistance
of the power supply and the resistor you switch in serie
For this reason R = R0 + R1
This diagram would be closer to the real world
output ^^ HD LED
|---|>|----+
HD+ o--[ R0 ]--o---[R1]---+ c |-----+
UHD0 UHD |---|(-----+ |
HD- o----------o---------------------------+
R0: circuit uncharged: no led.
UHD0: Voltage uncharged.
1) measure UHD0: uncharged
2) measure R0
For this we need one suplementary step:
R' = UHD0/15mA
We connect R' instead of the led and measure the voltage drop UHD'
So
R0 = (UHD0 -UHD')/15mA
Now we have
UHD0: The uncharged value of the led voltage
R0: The own resistence of the power circuit
Iled: The current trough the led (15mA)
R = UHD0/Iled
R1 = R -R0
Most circuitry has already it's own resistance R0, so it is possible you
leave R1 = 0.
Afterwards you need to determine the value of C
As Chris Ellis pointed out: T = 2pi.rc or as most engineers use to
calculate 6,25RC
So the value of C must be much greater the the time in seconds it flickers
C >> T/(6.25R)
Karl Lattimer wrote:
After sitting, almost transfixed on my mac's sleep light as it slowly
rises
and falls a little college electronics returned to me.
^^ HD LED
|---|>|----+
HD+ o--[ R ]--+ c |-----+
|---|(-----+ |
HD- o--------------------------+
Now I'm pretty sure this is right, off the top of my head, and would
relieve
the headache a hard disk light in a freevo can cause.
The only problem is I can't rightly remember the method of determining
the
values of R and c (my notes are long gone), I'll keep looking, and update
as
necessary and of course post a wiki. The thing is, what would be a good
timing? Should we try and time it so our breathing comes in time with it
as
we watch a movie?
Regards
Karl,
-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Freevo-users mailing list
Freevo-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/freevo-users
sorry for the second reply, I also should introduce myself a bit, i'am
currenlt studding for a-levels and will be going to uni to studdy
electronic engineering so are quite ok at electronics. I have put the
circuit through so circuit modellign software I have and it did not seem
to work. (this is not a 1005 accurate but i will also construct to have
a look, it is an excellent IDEA. I think what we may need is a RC
filter.
-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Freevo-users mailing list
Freevo-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/freevo-users
--
This message has been scanned for viruses and
dangerous content by OpenProtect(http://www.openprotect.com), and is
believed to be clean.
I must point out that T = RC not 2pi RC 2pi is used in the capacitor
reactance formular but not in the timne perioc for a RC circuits
Chris Ellis
-------------------------------------------------------
SF email is sponsored by - The IT Product Guide
Read honest & candid reviews on hundreds of IT Products from real users.
Discover which products truly live up to the hype. Start reading now.
http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click
_______________________________________________
Freevo-users mailing list
Freevo-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/freevo-users