Don, assuming each diode has a voltage drop of 3.6 volts, your series
string of 40 would have a voltage drop of 144 volts at rated current. (I
assume 20 mA) The red dot marks the positive terminal of the capacitor.
At only 20 mA the capacitor may level the voltage closer to the peak
value of the voltage You may want to use a 1000 ohm resistor and two
capacitors - one on either side of the resistor - a pi network filter.
Use a 1/2 watt or greater resistor. Using a multimeter check the current
in the circuit. Meter should be in series with the LEDs. Adjust the
value of the resistor to keep the current at or less than the rated
current for the LED's.
Check the spec sheet for your LEDs for actual ratings.
Best regards,
Bill Walden
.
Don Cooper wrote:
Speaking of LEDs... I'm wanting to use a large capacitor to level the
voltage off half-wave rectification (single std.diode isolating the
capacitor - [k.i.s.]) - for a big series string of 40 white LEDs that
are hooked up direct with a 100ohm resistor in series. It works, but
flickers at 60hz. It is running on the positive side of the sine wave
which I think peaks at 177v (110 RMS). While swinging negative
across the LEDs - the house current is a disconnect. They are diodes
after all.
It's a fairly bright and efficient light (probably). Unusually
oriented - the multiple inline elements produce "polarized shadows"
(only vertically aligned objects in the room have defined shadows -
this might make an interesting way to light cave formations!)
Hooked up to AC - the flicker is a bit bothersome. But making it "on"
all the time using a capacitor to reservoir the voltage, it will
appear much brighter. (A beefier load resistor might be in order to
maintain the constant rather than flickering wattage).
QUESTION: I found a big 820uF cap - rated at 200vdc. But it does not
have clearly marked pos/neg terminal. There is red paint on the base
rivet that holds the terminal on.
Is that the Negative or Positive side?
-WaV
A dog. A panic in a pagoda.
On 10/21/07, *Minton, Mark* <mmin...@nmhu.edu
<mailto:mmin...@nmhu.edu>> wrote:
There is a good layman's primer on LEDs and the physics
behind them in the September 2007 issue of Spectroscopy magazine.
You can read it here: <
http://www.spectroscopymag.com/spectroscopy/The+Baseline+Column/Light-Emitting-Diodes/ArticleStandard/Article/detail/457040?contextCategoryId=2324>.
Mark Minton
---------------------------------------------------------------------
Visit our website: http://texascavers.com
To unsubscribe, e-mail: texascavers-unsubscr...@texascavers.com
For additional commands, e-mail: texascavers-h...@texascavers.com
