"GregS" wrote in message
...
| In article , "WBH"
wrote:
| You can put led lights in series, but then you always have to switch more
| lights on than you need. The whole idea of led lighting is to be more
| efficient with DC and that translates to being able to switch lights
| individually. The only way to efficiently supply power to leds is by
using
| constant current regulators, that use PWM (pulse width modulation). Any
| other circuitry, be it transistor or Vreg, produces heat and is therefore
| inefficient. Cheap led drivers can be found he
| http://www.dealextreme.com/details.dx/sku.13553
| cheers,
| wbh
|
| Well I guess the regulators are cheaper than the leds now.
| At least these imports.
| These are interesting but what the hell are those prongs for ?
| Would be interesting to see the specs and the switching frequency.
| Free shipping fro Hong Kong. Good.
|
| greg
|
|
|
|
| "Geoff Schultz" wrote in message
| . ..
| | A couple of years ago I installed DoctorLED
| | (http://www.doctorled.com/p24.htm) Mars Dome interior lights throughout
| | BlueJacket. This was the first shipment of these to the US and I
literally
| | had to wait for them to get off of the container and into my hands
before
| I
| | could depart for the NW Caribbean. They may have changed the design
since
| | then, but this is what I've got.
| |
| | Anyhow, about a year later I realized that they were getting dimmer and
| | dimmer and recently took a failed unit over to a friend who's an
excellent
| | electronics engineer to determine what had failed. He found 2 problems
| with
| | the units:
| |
| | 1) There's a layer of thermal paste which is supposed to conduct the
heat
| | between the circuit board that the LEDs are mounted on and the aluminum
| | backing plate which also functions as a heat sink. For all intents and
| | purposes, there was too little paste to provide contact between the
two.
| | However, after running a working unit for about 10 minutes, there was
no
| | appreciable heat buildup, so we don't suspect that my problem was due
to
| | thermal overheating.
| |
| | 2) The basic design of the circuit is a transistor which limits the
| voltage
| | to 9V to 2 parallel stacks of 3 LEDs in series. This provides 3 V to
each
| | LED, which is just fine. However, the transistor is too slow to handle
| fast
| | transient voltage spikes, and there's no voltage dump circuitry on the
| | boards to handle this. A spike probably occurred somewhere along the
line
| | and fried some of the LEDs.
| |
| | DoctorLED will sell me replacement circuit boards at about 1/2 of the
cost
| | of the whole unit, which is still expensive. I plan to do that, but I
want
| | to protect against this happening in the future. All of the lighting is
on
| | 2 separate circuits. What can I do to protect against this happening
| again?
| | I was thinking about a 12 V DC to DC power supply. Any suggestions?
| |
| |
| | -- Geoff
| | www.GeoffSchultz.org
|

No idea what the prongs are for. I guess these drivers were made for a
specific application. I just de-soldered them and replaced them by wires.
Put heatshrink around the whole thing and put it in the back of the light
fitting. I use them to drive Cree leds. This is what it looks like:
http://www.flickr.com/photos/38407103@N07/ Total DC draw with all the lights
on: 0.9A.
They do produce some noise on the VHF, but that's acceptable as we only use
the interior lights when anchored. I've ordered half a dozen more, because
by the look of it the design has changed somewhat since I bought them and
I'm curious to see if they got rid of the noise.

wout