Experimenting with LEDs

W

William_H

Well-Known Member
Joined
28 Jul 2003
Messages
14,412
Location
West Australia
Visit site
I bought 10 of these 1W LEDs
http://www.banggood.com/Wholesale-1...ulbs-(3_2-3_4v-Or-10-piece-Pack)-p-27323.html
I finally got around to setting them up for brightness assessment in the dark. They really are amazingly bright. I wired up 5 in series and run them off a 15v transformer type plug pack. They were spaced about 1 metre apart on the roof of my outdoor living area. The light was brilliant. Certainly too bright for that intimate ambience.
At 1 w they need a heat sink. I devised a system using a piece of copper about 3cms long by 8mm wide. The metal base of the LED sits on this. To hold it down in place I soldered a piece of printed circuit board (not etched) cross ways about 6mm by 25mmm with the pc board soldered to the copper. I had made 2 cuts across the board so that there were 2 insulated pads sticking out each side. The lugs of the LED were soldered to these so holding the LED onto the copper.
http://www.ybw.com/forums/attachment.php?attachmentid=15624&stc=1&d=1326845931
Each LED drops about 3.4 volts at about .33 amps full power and even with heat sink get noticeably warm.
The light seems to radiate at a fairly wide angle about 100 degrees I would say.
For 12v operation one would use 3 LEDs in series and a 6 ohm current limiting resistor.
For safety if you use it with batteries on charge then use 12 ohm resistor. This will give less light and current at 12v but full brightness at 14v. Or you could devise a constant current regulator for 1 to 3 LEDs.
As you can see from pictures the face of the lED is a neat milky colored dot about 7mm in diameter which could fit well through a head lining. If however you used 3 LEDs in a small boat you will need switching to dim the lights because for many purposes they will be just too bright.
I hope this little story might be of interest for those stuck in winter with a hot soldering iron at the ready.
PM me if you want to discuss good luck olewill
 
Last edited:
I made a PWM controller about 8 years ago for controlling leds in RGB clusters. Quite fancied making a system and installing it on my boat project. LED's are cool. I just wish there were high power RGB leds in one package.. As yet not found any.
 
Am playing around with this at the moment.
Bought 100 high brightness LEDs of ebay, £2.78 post free.
Four in series, 12v supply and no appreciable heat and no resistor required.
Will mount them on to plain veroboard for my Stern light with one top one bottom and one each at either side facing Port and Starboard, this should ensure all round visabillity.
 
Good to see that some people are putting the 'Practical' back into Practical Boat Owner !

There's an amazing array of leds coming out of China: I like the look of the 'Straw Hat' types, which have a viewing angle of 140 degrees; then there are 5-chip types with outputs in the hundreds of thousands of mcd. Indeed, I'm finding that making a choice of what to play with next is very difficult.

2 points to ponder:
As a youngster I noticed that a room could be illuminated far brighter by 1 x 150 watt light bulb (remember those ?), than by 3 x 60 watts. Dunno why, maybe a physics expert could explain.

I can't prove this - but I hold a belief that the physical size of a wide-angle illuminating device is related to how far it can be seen. Which would suggest that a reasonably large diffusion screen (say, 5 square inches or so) might pay dividends. Have googled this topic several times, but to no avail. Airfield runway lights, vehicle lights etc are all typically of the same order of size. Must be a reason - but maybe it's a practical one rather than physics ?
 
Glad to see that you have recovered from the wind problems yuo had last year, and that you are spending your time pushing the limit of LED technology.
In 2004, I replaced single 10 watt tungsten bulbs with 30 led arrays, on a small pcb.
The light output was equivalent to your single 1 watt led!
 
Lundylad said:
Am playing around with this at the moment.
Bought 100 high brightness LEDs of ebay, £2.78 post free.
Four in series, 12v supply and no appreciable heat and no resistor required.
Will mount them on to plain veroboard for my Stern light with one top one bottom and one each at either side facing Port and Starboard, this should ensure all round visabillity.
Click to expand...
I expect your LEDs will fry themselves spectactularly when you install them on the boat. Current limiting, by resistor or a constant current source is essential for driving LEDS. No ifs or buts or exceptions. Perhaps the leds you bought have a built in current regulator, but I'd be very surprised. I guess the wiring you're using when testing them, in conjunction with the internal resistance of your power source, is providing an adequate current limit, which would explain why you haven't fried them yet.
 
Once the voltage goes up to 13.8v when the alternator kicks in you'll have 3.45v available for each LED. If that is above the Vfwd of the LED's the current will rise rapidly, if there's enough voltage available there will be a short flash of light and the LED(s) will stop working because the smoke will have escaped.
 
Thanks for the comments.
A work colleague has bought the same LEDs and has run them at 15v without them going up in smoke.
I am going to put two sets of four series LEDs in parallel and soak test them on a bench power supply before I even get to the stage of fitting them.

12v 2.0Ah supply 4 LEDs rated at 30mA max Vf 4v current consumption was
14mA
Again thanks for any thoughts, comments.
 
LED s and current limiting

LEDs seem to have a curve of current versus voltage although extremely steep. It is generally considered unmanageable to operate LEDs without current limiting however apparently it is possible. As said it is unlikely the LEDs will survive battery charging while turned on and of course brightness will diminish dramatically with voltage drop.
I suggest Lundylad look at LED current at various voltages of input. I think he will be frightened by huge current at voltages elevated only slightly.
I mention I ran 5 of these 1w LEDs off a transformer (plug pack) nominally 15vDC output. I started using a series current limiting resistor but soon discovered that the internal resistance of the plug pack meant they ran happily without current limiting resistor. (more correctly using the current voltage characteristics of the transformer rectifier filter combination.)(voltage falls dramitically with current) NB this won't happen with switch mode plug packs.
On my boat I use a NiCad battery and solar charging. This means that lights are always off when charging and the battery voltage is very stable around 12v over a wide range of charge state. So resistive current limiting is quite successful. I am wondering about building a switch mode current control but my soldering skills and design ability seem to have diminished. (Lazy) olewill
 
Beyondhelp said:
Couple of other things to consider:

http://www.amazplus.com/5m-smd5050-...or-strip-light-0945fkn505030rgb-p-255650.html

and:

http://www.amazplus.com/cree-3w-rgb-led-emitter-20mm-base-p-294685.html

Think I'll order some of those 3 watt RGB units they seem really well priced.


Edit: 10 of those leds now on the way :)
Click to expand...

I found some of the shelf constant current controllers here.. http://www.luxdrive.com/products/buckblock-a009-led-driver/

not so sure about RGB though.
 
To make decent current limited system for three colours isn't much harder than one, then you can have the option of white with colour mixing.

Other than that I don't know. I do lots of stuff with DMX so playing with one colour seems boring. I always like to keep projects flexible.

It would be quite cool to have colour control over your lights, even if there is no real reason.
 
You must log in or register to reply here.

Share this page

Top