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hosh
Feb 22, 2011, 7:00 PM
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Need help making an LED light. Finding some interesting things online, but need some specific help. Anyone who knows, please assist...?
hosh.
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Arrogant_Bastard
Feb 22, 2011, 7:02 PM
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Making an LED light? As in a single LED? Why? If it's some sort of school project thing then perhaps you should use the information they gave you. Otherwise, go buy one.
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Arrogant_Bastard
Feb 22, 2011, 7:04 PM
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Or were you using "light" as a verb. In that case, hook each terminal of a small battery (1.5V should be enough) to each of the leads on the LED. It should light up.
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gmggg
Feb 22, 2011, 7:59 PM
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Arrogant_Bastard wrote: Or were you using "light" as a verb. In that case, hook each terminal of a small battery (1.5V should be enough) to each of the leads on the LED. It should light up.
Or take a fresh razor blade and slowly scrape away the excess plastic. You can also trim the leads back to save those last few milligrams.
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hosh
Feb 22, 2011, 8:53 PM
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Not a school project, I'm long past my schooling years. And no, it's not a single light as in a bulb, I need to build a working LED flashlight, but a rather small one that fits in a particluarlly small space, for a toy I'm building for my 4 year old son. Would it seriously work to put a battery in there and connect the bulb directly?
hosh.
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edge
Feb 22, 2011, 9:08 PM
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hosh wrote: Not a school project, I'm long past my schooling years. And no, it's not a single light as in a bulb, I need to build a working LED flashlight, but a rather small one that fits in a particluarlly small space, for a toy I'm building for my 4 year old son. Would it seriously work to put a battery in there and connect the bulb directly? hosh.
You might have to add a resistor in series, depending on the LED and the battery.
When I was in Electronics Engineering school, one of my instructors had us do long calculations to figure out the value of said resistors. Once, after arriving at a value of 10k, I told him that the smallest we had in our lab was 220k. He said to "throw it in there, close enough."
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blondgecko
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Feb 22, 2011, 9:18 PM
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To design an LED circuit, the key things to know are that they only allow current to flow in one direction, they have a fixed voltage drop, and too much current will kill them in a flash (literally). To design your circuit, look up the voltage drop for your LED (it should be on the datasheet), subtract that from the voltage of your power supply, and choose a resistor to go in series that, according to (current)=(voltage)/(resistance) gives you a current below 20mA.
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Arrogant_Bastard
Feb 22, 2011, 9:24 PM
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blondgecko wrote: To design an LED circuit, the key things to know are that they only allow current to flow in one direction, they have a fixed voltage drop, and too much current will kill them in a flash (literally). To design your circuit, look up the voltage drop for your LED (it should be on the datasheet), subtract that from the voltage of your power supply, and choose a resistor to go in series that, according to (current)=(voltage)/(resistance) gives you a current below 20mA.
It's been awhile since I've worked hands-on with circuits, but you used to be able to get LEDs with integrated resistors set to run off of whatever standard voltage - usually 1.5 or 3. Get a bunch of those and just put them in parallel, hook up to a switch and a battery.
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hosh
Feb 22, 2011, 10:15 PM
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I've been told that I need some kind of a circuit board? Is this true, or will wires, resistors and a power supply (batteries?) work just fine?
hosh.
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blondgecko
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Feb 22, 2011, 10:24 PM
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hosh wrote: I've been told that I need some kind of a circuit board? Is this true, or will wires, resistors and a power supply (batteries?) work just fine? hosh.
No circuit board necessary. Just make sure to avoid shorting. It's as simple as battery(+)----resistor----led----(-)battery.
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blondgecko
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Feb 23, 2011, 12:03 AM
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I bought a bunch off ebay a few years back. Packages of 10 to 100 - prices worked out to less than 10c per LED in most cases. No complaints - but you'd want to reduce the current right down on those ones to avoid being blindingly bright.
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Arrogant_Bastard
Feb 23, 2011, 12:06 AM
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blondgecko wrote: I bought a bunch off ebay a few years back. Packages of 10 to 100 - prices worked out to less than 10c per LED in most cases. No complaints - but you'd want to reduce the current right down on those ones to avoid being blindingly bright.
I figured you could get cheaper but I wasn't going to waste more than a minute looking around. However, most of the cheap ones that I saw had viewing angles of 160 degrees or so. The ones above had 15-30, which I'd think for a flashlight type use would make a considerable difference.
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majid_sabet
Feb 23, 2011, 12:32 AM
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I converted most of my old headlamp to LED using Philips LED and I used another LED to drop the voltage from 4.5 to 3.7 or from 3.0 to 1.5 instead of using resistor. You have to remember that proper resistor keeps the voltage and current where you do burn too much power to keep the light on.
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hosh
Feb 23, 2011, 12:41 AM
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blondgecko wrote: hosh wrote: I've been told that I need some kind of a circuit board? Is this true, or will wires, resistors and a power supply (batteries?) work just fine? hosh. No circuit board necessary. Just make sure to avoid shorting. It's as simple as battery(+)----resistor----led----(-)battery.
But how do I know which resistor to use with which LED? I am really that ignorant...
hosh.
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Arrogant_Bastard
Feb 23, 2011, 12:56 AM
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hosh wrote: blondgecko wrote: hosh wrote: I've been told that I need some kind of a circuit board? Is this true, or will wires, resistors and a power supply (batteries?) work just fine? hosh. No circuit board necessary. Just make sure to avoid shorting. It's as simple as battery(+)----resistor----led----(-)battery. But how do I know which resistor to use with which LED? I am really that ignorant... hosh.
http://www.hebeiltd.com.cn/....resistor.calculator
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blondgecko
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Feb 23, 2011, 12:57 AM
Post #17 of 36
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majid_sabet wrote: I converted most of my old headlamp to LED using Philips LED and I used another LED to drop the voltage from 4.5 to 3.7 or from 3.0 to 1.5 instead of using resistor. You have to remember that proper resistor keeps the voltage and current where you do burn too much power to keep the light on.
This is only useful in cases where you need more than one LED. Swapping out a resistor for a diode that gives the same voltage drop will lead to exactly the same power usage. If you want to minimize waste power, make your battery voltage as close as possible to the LED voltage drop.
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Arrogant_Bastard
Feb 23, 2011, 1:05 AM
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blondgecko wrote: majid_sabet wrote: I converted most of my old headlamp to LED using Philips LED and I used another LED to drop the voltage from 4.5 to 3.7 or from 3.0 to 1.5 instead of using resistor. You have to remember that proper resistor keeps the voltage and current where you do burn too much power to keep the light on. This is only useful in cases where you need more than one LED. Swapping out a resistor for a diode that gives the same voltage drop will lead to exactly the same power usage. If you want to minimize waste power, make your battery voltage as close as possible to the LED voltage drop.
I'm amazed you were able to follow his writing at all.
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blondgecko
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Feb 23, 2011, 1:09 AM
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Arrogant_Bastard wrote: blondgecko wrote: majid_sabet wrote: I converted most of my old headlamp to LED using Philips LED and I used another LED to drop the voltage from 4.5 to 3.7 or from 3.0 to 1.5 instead of using resistor. You have to remember that proper resistor keeps the voltage and current where you do burn too much power to keep the light on. This is only useful in cases where you need more than one LED. Swapping out a resistor for a diode that gives the same voltage drop will lead to exactly the same power usage. If you want to minimize waste power, make your battery voltage as close as possible to the LED voltage drop. I'm amazed you were able to follow his writing at all.
I speak fluent gibberish.
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hosh
Feb 23, 2011, 6:31 AM
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Arrogant_Bastard wrote: hosh wrote: blondgecko wrote: hosh wrote: I've been told that I need some kind of a circuit board? Is this true, or will wires, resistors and a power supply (batteries?) work just fine? hosh. No circuit board necessary. Just make sure to avoid shorting. It's as simple as battery(+)----resistor----led----(-)battery. But how do I know which resistor to use with which LED? I am really that ignorant... hosh.
OK, here goes:
If I use this:
http://www.radioshack.com/...=3111495#tabsetBasic
with a 5 volt battery (or 3 AA batteries?), I'll need to hook it up using this:
http://www.radioshack.com/...sp?productId=2062350 right? Will I need anything else?
Oh, and does it matter if I have a on/off switch thrown in the mix? Will that affect any of the components that I'll need?
It should kind of go without saying that you'll want to have a way to turn it on and off, right?
hosh.
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blondgecko
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Feb 23, 2011, 7:20 AM
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hosh wrote: Arrogant_Bastard wrote: hosh wrote: blondgecko wrote: hosh wrote: I've been told that I need some kind of a circuit board? Is this true, or will wires, resistors and a power supply (batteries?) work just fine? hosh. No circuit board necessary. Just make sure to avoid shorting. It's as simple as battery(+)----resistor----led----(-)battery. But how do I know which resistor to use with which LED? I am really that ignorant... hosh. OK, here goes: If I use this: http://www.radioshack.com/...=3111495#tabsetBasic with a 5 volt battery (or 3 AA batteries?), I'll need to hook it up using this: http://www.radioshack.com/...sp?productId=2062350 right? Will I need anything else? Oh, and does it matter if I have a on/off switch thrown in the mix? Will that affect any of the components that I'll need? It should kind of go without saying that you'll want to have a way to turn it on and off, right? hosh.
Close - except that resistor is actually a 100,000 Ohm resistor (that's what the K refers to). You want 100 Ohms.
You could also go with something like this off eBay:
http://cgi.ebay.com/...;hash=item230dfac0aa
20 of them for 10 bucks, and they're already prewired with resistor for a 12V power supply. They'd still work at 5V, but would just be a bit dimmer - which may not be a bad thing, depending on your application. 8,000 mcd is bright enough so that it'd hurt to look directly at them.
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majid_sabet
Feb 23, 2011, 8:13 AM
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Arrogant_Bastard wrote: blondgecko wrote: majid_sabet wrote: I converted most of my old headlamp to LED using Philips LED and I used another LED to drop the voltage from 4.5 to 3.7 or from 3.0 to 1.5 instead of using resistor. You have to remember that proper resistor keeps the voltage and current where you do burn too much power to keep the light on. This is only useful in cases where you need more than one LED. Swapping out a resistor for a diode that gives the same voltage drop will lead to exactly the same power usage. If you want to minimize waste power, make your battery voltage as close as possible to the LED voltage drop. I'm amazed you were able to follow his writing at all.
I manage a 5 million dollar electronic lab and work with 290 electronic engineers. I think i know something about electronics.
here is what I do at home when I am bored
[url=http://www.imagehosting.com/]
(This post was edited by majid_sabet on Feb 23, 2011, 8:14 AM)
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majid_sabet
Feb 23, 2011, 8:20 AM
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blondgecko wrote: majid_sabet wrote: I converted most of my old headlamp to LED using Philips LED and I used another LED to drop the voltage from 4.5 to 3.7 or from 3.0 to 1.5 instead of using resistor. You have to remember that proper resistor keeps the voltage and current where you do burn too much power to keep the light on. This is only useful in cases where you need more than one LED. Swapping out a resistor for a diode that gives the same voltage drop will lead to exactly the same power usage. If you want to minimize waste power, make your battery voltage as close as possible to the LED voltage drop.
4.5 volt -.7 volt drop diode(in my case a LED)= 3.8volt which runs the Philips LED just fine. I use red led on top of the headlamp facing backward and run the white one to the front. almost all new leds now use a circuit that manages the vol and current by an IC which maximize the battery usage. few months ago me and some other engineer send a patent on a new circuit which could revolutionize the power usage but i wait a year and do more testing.
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edge
Feb 23, 2011, 2:13 PM
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Why not cannibalize one of these push-on LED lamps? About $7 and it will have everything you need, minus a seperate on/off switch that you can buy at Radio Shack or the hardware store?
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Arrogant_Bastard
Feb 23, 2011, 4:31 PM
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majid_sabet wrote: Arrogant_Bastard wrote: blondgecko wrote: majid_sabet wrote: I converted most of my old headlamp to LED using Philips LED and I used another LED to drop the voltage from 4.5 to 3.7 or from 3.0 to 1.5 instead of using resistor. You have to remember that proper resistor keeps the voltage and current where you do burn too much power to keep the light on. This is only useful in cases where you need more than one LED. Swapping out a resistor for a diode that gives the same voltage drop will lead to exactly the same power usage. If you want to minimize waste power, make your battery voltage as close as possible to the LED voltage drop. I'm amazed you were able to follow his writing at all. I manage a 5 million dollar electronic lab and work with 290 electronic engineers. I think i know something about electronics.
No, you don't. I'd be willing to entertain the idea that you're a janitor at a 5 million dollar electronics lab... but don't try to get all Good Will Hunting on me.
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