connect 10,000 LEDs in parallel
- Thread starter mousepad
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Hi Eric,
That's basically the idea by using the 24v switching power supplies; but keeping the voltage low enough to avoid any shock hazard.
Our OP seems to be a novice in electronics. I try to discourage "newbies" from experimenting with anything over around 45v due to the shock hazard.
The power supply I suggested is on sale, also what I felt was a reasonable compromise between his original idea (which would've wasted about 60% of the power applied), along with being a relatively safe voltage level to experiment with. Should the OP grow tired of watching 10,000 LEDs flash on and off, they'll still have a couple of decent power supplies they could use to power other projects.
Hi Sarge:
As you can see by my signature, I'm not quite as adamant about shielding our young'uns against those big bad old volts!
Some of my greatest revelations have resulted from getting knocked on my kiester. But, I suppose in light of our current generation, safety is a consideration. eric
I acknowledge that possibly safety is a primary concern. But fun is fun.
The guy didn't say where he intended to install this amazing poject, but if there's a wall outlet available (and there'd better be, to run those power supplies) then I'd suggest running it directly off the power line,with a reasonable voltage drop being given to a resistor and the rest to a string of LEDs in series. The LED strings could be doubled up per resistor, with the two sets carrying current in opposite directions. It's simple and efficient in its use of power, and the eye can't perceive a 60Hz flicker rate. Then the control of the light output could be via a solid-state relay.
Let's see, say 50 LEDs in each serial string, you'd need 200 strings total to get 10,000, so that's 100 each way, and they're only on 50% of the time, so let's give them 40mA each, that's 4 amps. Not too scary in terms of power input.
Of course, the LEDs will hardly conduct at all until the power line reaches about 2V per diode, so current draw is intermittent. I'm not sure what that does to the power line. Is it something to worry about?
The guy didn't say where he intended to install this amazing poject, but if there's a wall outlet available (and there'd better be, to run those power supplies) then I'd suggest running it directly off the power line,with a reasonable voltage drop being given to a resistor and the rest to a string of LEDs in series. The LED strings could be doubled up per resistor, with the two sets carrying current in opposite directions. It's simple and efficient in its use of power, and the eye can't perceive a 60Hz flicker rate. Then the control of the light output could be via a solid-state relay.
Let's see, say 50 LEDs in each serial string, you'd need 200 strings total to get 10,000, so that's 100 each way, and they're only on 50% of the time, so let's give them 40mA each, that's 4 amps. Not too scary in terms of power input.
Of course, the LEDs will hardly conduct at all until the power line reaches about 2V per diode, so current draw is intermittent. I'm not sure what that does to the power line. Is it something to worry about?
Well, I have a puny 250W ATX form factor supply that I converted into a bench supply.
The +5V output can supply up to 25A, which would be enough to light 1,250 2-LED strings, or 2,500 LEDs; each string would need a >= 50 Ohm limiting resistor. Since 51 Ohms is a standard value, that would be the one to go with.
The +12V output can supply up to 8A, enough for up to 400 5-LED strings, each with a 100 Ohm limiting resistor, so that's another 2,000 LEDs.
Just a single puny 250W ATX form factor supply, and it's almost enough power for half of the LEDs.
If our OP could salvage a couple of higher wattage ATX form factor supplies, they wouldn't have to spend any money on supplies at all; it would be far safer than attempting to use mains power (which is strongly discouraged around here), not to mention far easier to troubleshoot when a few LEDs die here and there.
The +5V output can supply up to 25A, which would be enough to light 1,250 2-LED strings, or 2,500 LEDs; each string would need a >= 50 Ohm limiting resistor. Since 51 Ohms is a standard value, that would be the one to go with.
The +12V output can supply up to 8A, enough for up to 400 5-LED strings, each with a 100 Ohm limiting resistor, so that's another 2,000 LEDs.
Just a single puny 250W ATX form factor supply, and it's almost enough power for half of the LEDs.
If our OP could salvage a couple of higher wattage ATX form factor supplies, they wouldn't have to spend any money on supplies at all; it would be far safer than attempting to use mains power (which is strongly discouraged around here), not to mention far easier to troubleshoot when a few LEDs die here and there.
Did Mousepad get a batch of scrapped-out small LED's (not intended for lighting)? With LEDs made for lighting purposes, such as the Cree XR-E series, you get 80 lumens per LED, and 50 LED's replace a 250W sodium-vapor street light. Ones made as indicators might be only 1 lumen each (it's hard to tell, they aren't rated in comparable units, and I don't know if the lumens/watt would be good enough to save energy).
You have to heat-sink high power LED's or large arrays of any sort of LED, as well as providing a current-limited supply to each string. We're using a switching power supply chip to regulate the current for each string of 10 LEDs, which is a little expensive.
High-efficiency LED's are so much more efficient than anything else (including all varieties of arc and flourescent lighting) that you can give up some of your efficiency by using resistors for current-limiting, and still be ahead. E.g., rectify the AC line for about 150VDC. String enough LED's in series for about 100-110V forward voltage. Drop 40-50 V through a resistor. You've got about 70% efficiency, times whatever the internal efficiency is of the LED's themselves, and that beats anything else.
But you must keep your LED's cool. High-temperature = short life, and they do generate heat internally. You'll see many LED fixtures on the shelves at Walmart, made by various light bulb and fixture manufacturers, and most of them are going die prematurely, because it's hard for a guy that's used to working with bulbs that can burn your hands to keep in mind that merely getting warm is a bad, bad thing for electronics. In the street lamps we're making, the circuit board is laminated onto a sheet of aluminum, which bolts to a fin heat-sink, with fans - AND we glued some thermocouples onto the prototype to prove that this was good enough.
You have to heat-sink high power LED's or large arrays of any sort of LED, as well as providing a current-limited supply to each string. We're using a switching power supply chip to regulate the current for each string of 10 LEDs, which is a little expensive.
High-efficiency LED's are so much more efficient than anything else (including all varieties of arc and flourescent lighting) that you can give up some of your efficiency by using resistors for current-limiting, and still be ahead. E.g., rectify the AC line for about 150VDC. String enough LED's in series for about 100-110V forward voltage. Drop 40-50 V through a resistor. You've got about 70% efficiency, times whatever the internal efficiency is of the LED's themselves, and that beats anything else.
But you must keep your LED's cool. High-temperature = short life, and they do generate heat internally. You'll see many LED fixtures on the shelves at Walmart, made by various light bulb and fixture manufacturers, and most of them are going die prematurely, because it's hard for a guy that's used to working with bulbs that can burn your hands to keep in mind that merely getting warm is a bad, bad thing for electronics. In the street lamps we're making, the circuit board is laminated onto a sheet of aluminum, which bolts to a fin heat-sink, with fans - AND we glued some thermocouples onto the prototype to prove that this was good enough.
