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The LED driver described on this page is based upon schematics for the NUD4001 IC provided by OnSemi.
It is almost as simple to create as the LM317 driver described on the Drivers page
but much more flexible and reliable.
All the information needed to understand the NUD4001 IC can be found on the OnSemi
site from their White paper PDF here.
I'll try and summarize the best I can and offer printable schematics, board layout
and positive resist image at the end.
The NUD4001 IC is a simple constant current driver that requires only 1 resistor
to function in it's simplest form. As this will work, it is limited to a very
small supply voltage vs LED voltage variance. I do not know the actual variance, but if the
supply voltage is some percent greater than the LED voltage, the IC will overheat
and realease all its magic smoke. To prevent this, the circuit must be designed
with either a large copper pour to act as a heat sink (about 2 cm2 of 2oz copper may
work for driving a single Luxeon I from a 12 vdc source), or you need to add a transistor.
Transistors are cheap and easy to use so I saw no reason to exclude the one in their
schematic.
I have made a couple of changes from the source schematics.
-
First off, I separated the dimmer and made it its own board.
In its place are two sets of headers to plug the dimmer board directly onto the
driver board to add the functionality if I need it. Although the schematics
do not show it, I recommend using a female header for the power pins (J2) and a
male header for the switch pins (J1). This will keep you from accidentily
shorting out the driver (there are no fuses on this board so a short would probably
fry the bridge rectifier instantly). If you are not using a dimmer board,
simply jump J1 with a standard jumper sleeve.
- Secondly, I have replaced the SMD (surface mount devices) with suitable
through-hole components. This makes the entire board easier to solder but
does add considerably to the overall size. I did not add a recommended heat
sink for the TIP42C transistor. If you are planning on driving 3 Luxeon I
LEDs from a 12vac supply (outdoor landscape transformer), no heatsink is necessary.
However, if you are going to drive a single Luxeon I LED with the same power source,
the bigger the heatsink the better. On a side note: the TIP42 series of transistors
is extremely durable. I had attempted to use copper stick-on
heat sinks designed for computer memory in the place of a traditional bolt-on heat
sink. The transistor got so hot the sticky pad melted and the heat sink slid
off. I did not realize this had happened for over 1/2 hour. The transistor
was extremely hot (burned my finger on it), but still doing it's
job...
I have taken the plung and had professionally etched driver and dimmer boards produced
for the NUD4001 chip. The kicker is I did not double-check my schematic pin line-ups so the
dimmer board cannot plug directly into the driver - they need wired together (I inadvertently
swapped the signal and source pins). If interested, component kits, and completly assembled
drivers can be purchase from me. I am simply doing this as a courtesy at this point so if you
are interested in these items, drop me a line (via the web administrator link at the bottom of the
page) and we can set something up. If you are more of the do-it-yourself type and are
interested in making your own drivers with this circuit here are the schematics, board layout and positive resist mask all in one
convinient PDF: NUD4001 LED Driver**
**If you feel the need to place a link to this PDF on your site,
or copy the PDF and place it on your site, please be respectful by giving credit
and a link to BoilingPondsCemetery.com. While the schematic is not proprietery
(but may be Copywrited by Semiconductor Components Industries, LLC) it does take
time to convert the schematics into a single-sided workable board.
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