Bob,
What Dr. Gerald said is totally correct. I would appreciate myself a working
formula for calculating LED at 3 an 5 volts to operate on 12vdc. Dr. G. can
you give us something to put into our calculator please.
No problem exists in voltage regulation for me due to the nature of the
resistor and the LED which after all is just a diode, just like Dr. Gerald
said. Like a capacitor, there is a +/- range percentage that I chose for the
24v conversion and the range is more than sufficient with no price
difference. I can't remember the resistor I used, but it seems like the
operating voltage of the diodes were about three volts and there is a chart
I used at ACE in Houston. They resistors do not ever get hot that I can ever
feel with my very sensitive fingers. They just don't heat and the LED's have
been on since 1999.
My long time application is for an elevator I built in my home. Very vintage
in style, welding, and components, it serves need well. I had a multitude of
choices, since I am in the Forklift and Machinery business (presently on
hold) and so I chose a 24 volt system. I mounted all the noisy hydraulics in
a panel and placed it outside of my home. There are therefore no batteries
or hydraulics or oil in my home. I built a safety redundant system and
automated doors on weights that open and close from remote location without
attendance. There is a redundant system with view for any failure of the
lift hydraulics with flow failure even under pressure, back to the
reservoir.
Anticipating the needs of handicapped, I have "call buttons" at both hallway
approaches downstairs, upstairs, and on the elevator itself. The buttons had
to be illuminated for total darkness purposes. That is ten illuminated
buttons and I was able to get green for go and red for stop in LED. I needed
flow control due to the nature of micro milli volt contactors to stop eddy
current from the demands of high ampere draw 24v pump and heavy contactor. I
also wanted operation indicators at the control panel. Both needs were
accomplished with dual-direction dual lamped single LED's in again, red and
green colors to help me when in the pantry and blind to actual operation of
the outside unit or the elevator itself. I further added event-stop toggle
switches at the control panel and path the LED's to help indicated mode at
the panel.
I chose 24 volts to reduce initial LRA (locked rotor amp) draw, which is
about half of the 12v pumps, and safer than the 36 and 48 volt systems that
further reduce ampere draw, wire size, but get up in amps akin to a welder
in the event of some sort of catastrophic failure. I once saw a crowbar
dropped from an elevated scissor lift into the 120vdc battery rack
containing 10 12v batteries. Sure was pretty at the first explosion! The
120v dc systems were popular because you could run a lot of standard tools,
but had to be abandoned due to the inherent safety issues of some real idiot
workers. I digressed and am sorry.
Anyway, I chose 24vdc over ac power due to the nature of being on a elevator
in any type of power failure. The unit never operates on ac, which is only
used to keep the batteries up tight daily. The run time without charging is
two weeks.
I bet people are sick of this topic. I'm sorry, but Dr. G has is a walking
computer of knowledge and I never seem to learn enough.
-Eddie-
> I also have a burning interest in LEDs. Since they are so sensitive to over
> voltage could you send me information (part number?) on what you use to keep
> the voltage correct. I am concerned as charging voltages can be as high as
> 14 volts. Are you using a SCR or something else to fine tune the voltage?