I picked up a LED panel (About 1"x 2 1/2"x 3/16") from American Science & Surplus ( sciplus.com ). It's supposed to glow a nice bright green at 4.2 volts, 325 mA. I put it (very crudely) into a project box, wired up w/ a 9 volt battery & a 50 ohm resistor - got a nice green nightlight, similar in output to an EL type light. Output on one battery has been well over 24 hours continuous, w/ noticeable drop in output as the battery drains. Would like to set up a regulated supply for it at some point. The panels run about $2.50 each. Might be interesting for you experimenters.
LED panel
- Thread starter Flotsam
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Lux Luthor
Flashlight Enthusiast
Flotsam,
How bright is that thing? 325ma at 4.2V is a fair amount of power. You might as well run an LS.
How bright is that thing? 325ma at 4.2V is a fair amount of power. You might as well run an LS.
It's not that bright - similar to an EL nightlight. I was looking for a way to drive the EL nightlights from a battery pack - I would need a power supply that puts out AC, and unfortunately my electronics background is fairly nonexistent. Then I ran into these things - seems to have the effect I was after (sort of like a Krill light). Anyone got a schematic for such a thing?
It was really an excuse to play around w/ making a light - first result is very crude. Would like to make a regulated supply for it, and maybe run it off AA's.
It was really an excuse to play around w/ making a light - first result is very crude. Would like to make a regulated supply for it, and maybe run it off AA's.
Evan
Enlightened
I saw those, too. I have a similar panel here and pealed back the transluscent to to see a series-parallel array of surface mount green LEDs. I'd expect it to be a bit brighter than EL.
One thing for sure, it will last a lot longer as an EL in continuous use seems to lose a lot of brightness in a year or two.
There is a simple circuit using an LM317 and one resistor to current regulate when you have lots of voltage and/or power to spare (it'll waste at least 3 volts) See the bottom of page 15 in The LM117/LM317 datasheet (note: the data sheet is big, about 700K, and there is probably a better data sheet somewhere as this one is for surface a mount version of the chip). You can get the LM317 at lots of hobby electronics companies for 40 cents or so and comes in a TO92 case that is small but only good if it has to burn 625mW or less, or the TO220 which is just a little bigger but can handle over an amp
You might also try a switching regulator, but though they are more efficent, unless you can find a suitable board already built, they can be tough to build. I've just begun to play with a little 3cm square board I got out of a cellular phone car adapter. It's based on an 8 pin IC KA340653A and looks like it could regulate voltage or current each set by changing one resistor. It got my attention at a hamfest as it was only 50 cents and claimed to work at 12 or 24 volts and so it had to contain a regulator.
One thing for sure, it will last a lot longer as an EL in continuous use seems to lose a lot of brightness in a year or two.
There is a simple circuit using an LM317 and one resistor to current regulate when you have lots of voltage and/or power to spare (it'll waste at least 3 volts) See the bottom of page 15 in The LM117/LM317 datasheet (note: the data sheet is big, about 700K, and there is probably a better data sheet somewhere as this one is for surface a mount version of the chip). You can get the LM317 at lots of hobby electronics companies for 40 cents or so and comes in a TO92 case that is small but only good if it has to burn 625mW or less, or the TO220 which is just a little bigger but can handle over an amp
You might also try a switching regulator, but though they are more efficent, unless you can find a suitable board already built, they can be tough to build. I've just begun to play with a little 3cm square board I got out of a cellular phone car adapter. It's based on an 8 pin IC KA340653A and looks like it could regulate voltage or current each set by changing one resistor. It got my attention at a hamfest as it was only 50 cents and claimed to work at 12 or 24 volts and so it had to contain a regulator.
Hemingray
Enlightened
These LED "panels" were used for LCD display backlighting. I've seen then at JameCo and others.
The LM317 current regulator/limiter is pretty simple, connect a 1/4 watt resistor between the "Adjust" and "Output" pins. For setting the desired current, use R = 1250/I. R is Ohms, I is mA.For example, a 62 ohm resistor gives 20 mA, etc. Feed the DC source into the "input" pin and take the current-regulated DC off the "adjust" (not the output) pin.I've been doing this to the TO-220 devices for years. If you're going to full-power a Luxeon, use a 1/2 or 1 watt resistor, and heatsink the tab - note that the tab isn't a ground, so don't ground it unless you like buying new LM317s, LEDs and explaining what that smelly blue smoke is...
/ed in NH
The LM317 current regulator/limiter is pretty simple, connect a 1/4 watt resistor between the "Adjust" and "Output" pins. For setting the desired current, use R = 1250/I. R is Ohms, I is mA.For example, a 62 ohm resistor gives 20 mA, etc. Feed the DC source into the "input" pin and take the current-regulated DC off the "adjust" (not the output) pin.I've been doing this to the TO-220 devices for years. If you're going to full-power a Luxeon, use a 1/2 or 1 watt resistor, and heatsink the tab - note that the tab isn't a ground, so don't ground it unless you like buying new LM317s, LEDs and explaining what that smelly blue smoke is...
/ed in NH
