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Noswal
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« on: March 16, 2008, 06:14:31 AM » |
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Domestic AC as in 125 volts and 15 amps, grounded. I want to make a strip of LEDs (as much as possible) and control them with a dimmer.
So how should I go about this?
-Noswal
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MrbLOB9000
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« Reply #1 on: March 16, 2008, 07:29:10 AM » |
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um... like a million?
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Noswal
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« Reply #2 on: March 16, 2008, 07:40:53 AM » |
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What!? Really!? How do you calculate that? Wouldn't you blow a circuit?
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MrbLOB9000
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« Reply #3 on: March 16, 2008, 08:54:55 AM » |
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I don't actually know, but seriously, you'd probably run out of space before you ran out of power, LEDs take VERY little power and if you're dedicating a full circuit to it, shit man.
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hugh
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« Reply #4 on: March 16, 2008, 10:47:24 AM » |
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what i was gonna say. whole reason LED's are used so much is because of how non-existent their power drain is
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Connor
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« Reply #5 on: March 16, 2008, 02:22:26 PM » |
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The Voltage Drop across an individual LED is usually 1.5-2V (some exceptions depending on model) so run in series - you would get 60-80. However most likely you're going to run each LED in series with a resistor but in parallel which depending on your resistor could be a handful or couple of hundred - A quick calculation given 1K resistors on a 12V circuit (dropped by transformer/rectifier) would give 500 LEDs (Assuming a 5A domestic lighting circuit dedicated to it ) Your next problem is the dimmer circuit - it's not as easyto dim LED's as Light Bulbss an article here explains why http://66.102.9.104/search?q=cache:j3XTyChtCP4J:www.cpemma.co.uk/dimleds.html+dimming+LED&hl=en&ct=clnk&cd=3&ie=UTF-8Also domestic dimmer switches do not alter voltage - Instead they alter the duty cycle of the Light Bulb making them unsuitable for this circuit. |
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VorLonUK
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« Reply #6 on: March 16, 2008, 07:11:24 PM » |
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White Led's around say 10,000 mcd's will have a rating around 3.5volts and 30ma (milliamps). One thing with Led's is you need to ensure they are current limited, so a resistor provides that. So at say 12volts DC a 3.5Volt led @ 30ma (say on a modded illuminated PC) would need a 283ohm resistor. That's not a size you can get, so you would use the next available option, in this case a 270 ohm readily available resistor. The wattage then has to be calculated which is 0.25watts, so a 0.5 watt rated resistor would be chosen, so to have that safety margin.
Calculations:-
For resistor value.
Supply Voltage minus LED's forward voltage rating over the LED's rated current = Resistor (in ohms) required
For resistor Wattage.
Supply Voltage minus Led's forward voltage multiplied by Led's working (calculated (as above) current rating.
Obviously the mains is AC, and led's require a DC or Switch-mode supply. So rectification or a AC-DC PWM controller are required (the latter easily aiding light intensity dimming etc). There are loads of assemblies now available, which have all the required "electronics" within the light fitting itself. Many of these will just replace a standard home tungsten lamp.
Some of the only concerns have been the light output and the possible damage to eyes. The US didn't have any standards on this a couple of years ago, where Europe did and this caused some Confusion. Also Europe coupled LED's into the Laser standard, so Led's would fit into one of the Classes. Euirope now has taken the LEd's out of the laser category regs and they are now in the lighting regs.
The most dangerous Led's are the UV ones and some of the Blue's, so be careful if you are messing with some very high brightness led's
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Intuit
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« Reply #7 on: March 17, 2008, 07:33:41 AM » |
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VorlonUK, man I cover up or disable the LEDs that come in all sorts of devices that didn't used to. Those bright-ass blue LEDs in optical drives I cover up. Game Controller I covered-up. (damn thing could light up a room) Bought a laptop Mouse that had a bright-ass LED in it that they didn't even bother to advertise ?! Umm, it already has one... it's an optical mouse. Why add another ? Just wasting power (albeit very little) and taking years off my eyesight, opened the sucker up and cut one of the leads on the LED. Years ago they used to make them exceptionally bright on televisions but somewhere along the line they got a clue. I actually can't think of a single modern device I've purchased, with exception to an iPods, PC power supplies, harddrives, that does not have an LED or LED-display. Quantum Fireball HDs for their tiny sizes have surprisingly bright surface-mount LEDs and I know my laptop has them in places that aren't even visible. (they run in standby) :roll: Noswal, be sure to send us a snapshot.  http://imageshack.us/http://www.imageshack.us/I would imagine that you could basically create sub-units for your array(s) and that would alleviate the component-level power challenges and should improve efficiency. I guess the better question is, not how many you can use, but how many can you afford ? Devices with dimmer ICs for their LEDs are rare but I have seen one recently in a Dell Inspiron 6000 laptop. The dimmer circuit was easily audible by the way... |
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VorLonUK
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« Reply #8 on: March 17, 2008, 07:31:13 PM » |
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VorlonUK, man I cover up or disable the LEDs that come in all sorts of devices that didn't used to. Those bright-ass blue LEDs in optical drives I cover up. Game Controller I covered-up. (damn thing could light up a room) Bought a laptop Mouse that had a bright-ass LED in it that they didn't even bother to advertise ?! Umm, it already has one... it's an optical mouse. Why add another ? Just wasting power (albeit very little) and taking years off my eyesight, opened the sucker up and cut one of the leads on the LED. Years ago they used to make them exceptionally bright on televisions but somewhere along the line they got a clue. I actually can't think of a single modern device I've purchased, with exception to an iPods, PC power supplies, harddrives, that does not have an LED or LED-display. Quantum Fireball HDs for their tiny sizes have surprisingly bright surface-mount LEDs and I know my laptop has them in places that aren't even visible. (they run in standby) :roll: Noswal, be sure to send us a snapshot. http://imageshack.us/http://www.imageshack.us/I would imagine that you could basically create sub-units for your array(s) and that would alleviate the component-level power challenges and should improve efficiency. I guess the better question is, not how many you can use, but how many can you afford ? Devices with dimmer ICs for their LEDs are rare but I have seen one recently in a Dell Inspiron 6000 laptop. The dimmer circuit was easily audible by the way... Many that have been picked are far too bright for the application. Another thing too on some of the ways to Dim Led's, such as used in Led torches, is as the Led is "pulsed" (PWM) be careful when examining machinery with it! Especially checking under the hood of your car! As they use PWM for brightness control, it's easy to get the "stroboscope" affect. For instance, if i adjust say a PC fan to a certain speed then view it with a PWM Led torch I can make the the blades of the fan to appear to be stationary. Bit like setting the timing up on your car with a strobe light. |
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Noswal
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« Reply #9 on: March 18, 2008, 07:55:39 AM » |
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I've spend several days trying to understand most of the stuff you guys posted without luck. My initial intention with the led strips was to make a backlight for my new lcd tv. I wanted a brightness control because I thought the brightness of the backlight should be dependent on the ambient lighting.
But with dropping prices on lcd tv's and immaturity of HD programming, my dad decided to return it for now and purchase one in the future.
Meanwhile, I'm going to make my led strips. Since we're returning the one we have, I'm going to try to buy one with usb ports in the back and power the strips from there. Because usb operates on 5v, there's no need for resistors (right?). And is there really no simple dimming device out there?
-Noswal
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Noswal
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« Reply #10 on: March 18, 2008, 07:58:46 AM » |
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What companies make tvs with usb ports?
-Noswal
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Connor
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« Reply #11 on: March 18, 2008, 11:21:06 AM » |
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I've spend several days trying to understand most of the stuff you guys posted without luck. My initial intention with the led strips was to make a backlight for my new lcd tv. I wanted a brightness control because I thought the brightness of the backlight should be dependent on the ambient lighting.
But with dropping prices on lcd tv's and immaturity of HD programming, my dad decided to return it for now and purchase one in the future.
Meanwhile, I'm going to make my led strips. Since we're returning the one we have, I'm going to try to buy one with usb ports in the back and power the strips from there. Because usb operates on 5v, there's no need for resistors (right?). And is there really no simple dimming device out there?
-Noswal Why doesn't your TV already have a backlight(this is the light that makes the screen glow ), or do you mean an Ambilight like Philips LCDs have which provides ambient lighting to the room? Either way, you do need to worry about resistors on USB - with no other devices a USB port can produce at least 500mA which is too high for your LEDs. I get the feeling you're trying to run before you can walk - the electronics are farily simple try getting a radio shack/maplin starter kit to understand the principles behind these circuits or just buy a ready made USB/5V LED Panel. |
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Intuit
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« Reply #12 on: March 18, 2008, 05:34:37 PM » |
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Long ago I've seen USB flashlights at stores. Pretty useless product if you ask me but I suppose they were created for some (unknown) reason. Maybe they were just supposed to charge via USB ?
Anyway since they probably sold poorly if at all, you likely won't find them in stores any longer but should still be available online somewhere.
Get it for next to nothing, open it up and see what makes it tick.
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Reflex
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« Reply #13 on: March 18, 2008, 06:24:40 PM » |
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I hope your not planning on replacing the built in backlight on your tv, that would be bad..
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Intuit
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« Reply #14 on: March 18, 2008, 06:30:12 PM » |
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It also occured to me that subsidizing, modifying or replacing the inbuilt backlighting would likely throw the color and blacklevel way off. The backlight is specifically calibrated to the display. Different light sources output light at different amounts depending upon the particular wavelength. It's why clothing, furniture and cars can be varying shades of different colors depending upon the type of flourescent lighting they're under, as well as whether they're in the sunlight. Scanners use special types of LEDs and their software are specifically calibrated to the type of LED(s) used in them. In short, it may be interesting to try, but probably will not work.
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Reflex
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« Reply #15 on: March 18, 2008, 07:55:40 PM » |
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The LED's used in LED backlit tv's are extremely small and densly packed, they have to be to replace a CFL backlight and still be bright enough to use. Your not going to get LED's like that at a regular electronic supply store, and your not going to be able to create a suitable backlight with a breadboard and soldering iron.
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Noswal
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« Reply #16 on: March 19, 2008, 04:11:16 AM » |
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I guess I should have made it clearer. I meant backlight as in something like ambilight, not the actual lcd backlight. That would have been insane to replace with leds.
Yes, I am trying to run before I can walk. The starter kit and flashlight are great ideas; I'll start there.
-Noswal
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Timster
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« Reply #17 on: March 20, 2008, 06:33:50 AM » |
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I've seen ready-made strings of LED lights at places like Lowes and Walmart.
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Connor
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« Reply #18 on: March 20, 2008, 10:25:33 AM » |
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I've seen ready-made strings of LED lights at places like Lowes and Walmart. IKEA do them as well, There are also kits on EBAY that do the same thing. |
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Intuit
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« Reply #19 on: March 20, 2008, 04:56:38 PM » |
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What about LED Christmas Tree lights ? (may be ultra expensive though)
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Timster
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« Reply #20 on: March 22, 2008, 03:35:34 AM » |
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The LED Christmas lights I've seen were molded over with plastic bells and globes. With a little Dremel work, they can be trimmed down so they wouldn't look so seasonal.
To save money, check out the dollar stores and surplus outlets. They go on clearance right after Christmas, so there's still a chance they'll be in the clearance bins.
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