Nishant3789 Posted December 23, 2002 Share Posted December 23, 2002 hey well yesterday i set up an LED moonlight. the way it works is its a bright LED thats rated at 2600 mcd ( milla candel sumthings). anyways, its rated at 3.7 volts and a min of 20 amps and a max of 50 amps. 30 degree vewing angle. baseically it gives of sort of a spotlight. the LED itself is a Blue one thats 468 nm whcih is slightly above the actnic range but is supposedly great for moonlights and putting fish and corals in the "mood". the way i wired it up was i got a 4.5 volt AC adapter from an old CD player powersupply. I cut off the bit which u plug in and took the wires out so that they were bare, then i took one of the wires and attached a 47 ohm resistor to it and then resisotr to one side of the LED not sure if it was teh positive or negative too lazy to check. then the other wire to the remaining side of the LED. then i plugged it in and crossed my fingers and whoopee it lit up. it was pretty. i dont have this in a hood i just sorta have it sitting bare on my glass top for the tank. i do think thought aht this would fit in very very easily into a hood all it would take i woudl think is some electrical tape or ducktape or sum glue or s nail or two. It gives of this cool shimmering effect i think that all these MH users have been bragging about, and i can see why they wanna brag cuz it looks BEAUTIFUL!. Since the tank is in my room it makels a simply splendid nightlight. All the materials i mentioned were baught at Radio Shack cept for teh AC adapter whichi already had. the rest of it cost a grand total of like $5.12. i think the adapter would be no more than 15 bux, so for a max of 20 dollars you can have ureself a damned good light. teh AC powersupply u can use other AC adapters but u would hve to calculate the amount of resistance you would need. i plan on getting 2 more LEDs though im not too sure how to attach more than one to one powersupply.... well its like 3 am right now and i cant find the camera ill post a pic of it later. hope this info helps! nishant Link to comment
glazer Posted December 23, 2002 Share Posted December 23, 2002 I made myself a little nite light gizmo like you are describing Nishant.... used two of the blue LED's mounted in a "project box" all parts from Radio Shack.... um, the suction cup in the center is there as I stick it on different tanks but will be mounting it permanently in a hood I'm working on.... anyway on to my question. I'm no electrical weeeezard here so wondering if I screwed up or there will be a problem.... anytime I hear about anyone making these, well SINCE I did mine I hear them tell of putting a resistor on them.... uh, well why is that? I just cut the plug off the transformer and soldered the two wires right to the LED's....no resistor, no nada. It works fine and has been working for a few months now. Do I need to change that? What could happen with the way I have it now... transformer blows or bulbs cook? Link to comment
Nishant3789 Posted December 23, 2002 Author Share Posted December 23, 2002 well by the looks of it im guessing u are riuning a 3.7 volt LED and since u have a multi voltage adapter im guessing ure putting it on the lowest setting 3 volts? well then ure probably not running it at full voltage and ure not getyting it as bright as you could be. at least i think thats what it is, either taht or ure overdriveing them with it on the 4.5 volt setting and ure going to deceease the ife of the LED considerably... well i hope iot helped pictures coming in a few hours not to worry nishant Link to comment
leesnuts Posted December 23, 2002 Share Posted December 23, 2002 I'm not an expert but it's all about current. LED need a resistor to draw away some of the current to protect the diod. If you don't have a resistor its ok but most of the current is running through the LED which will burn it out. Depending on the LED you have, you have to run different Resistor Impedance to get the Brightness that you want. An LED would last almost forever if set up properly. Link to comment
Inpha Posted December 23, 2002 Share Posted December 23, 2002 The AC adapter is working like a resistor in this case. As long as the AC adapter has variable voltages and you match it to that of the LED's you should be fine I'm thinking... (no expert...) Link to comment
glazer Posted December 23, 2002 Share Posted December 23, 2002 The LED's that I am using are supposed to be 5 volts with a max of 6. I have the two of them tied together and the wires off the transformer soldered directly to the leads off the bulbs.... I run the transformer at the 5 v setting. They are indeed bright and work beautifully. I don't know if any of this helps.... so before I tear it apart to mount it in my hood do ya think I need one of the resistor things? And if I do, could ya help a guy out and tell me EXACTLY which one... like I said, I'm electrically challenged...hehehe Link to comment
Nishant3789 Posted December 23, 2002 Author Share Posted December 23, 2002 well then ure a lucky man i cant find anythng that bright whats teh mcd on that thing? The adapter should be fine and i dont think you will need a resistor. hope this helps nishant Link to comment
glazer Posted December 23, 2002 Share Posted December 23, 2002 Nishant... in my post above where I typed LED's is the link to the page at the Radio Shack..... "Typical MCD is 300" Haven't a frickin' clue what that means.... wait, I'm going to totally wing it here.... um, minimum OR maximum current draw? maybe? Link to comment
Nishant3789 Posted December 23, 2002 Author Share Posted December 23, 2002 oooh ok well how bright does the LED seem to be? i mean does it make like a spotolight on your tank? is it REALLY noticable? or is it pretty dim? nishant Link to comment
leesnuts Posted December 23, 2002 Share Posted December 23, 2002 Well if you have different resistors with different Impedances, try them. To get the maximum brightness that your LED can offer its just a trial basis. A resistance subsitution board will be the best to find the right Impedance value. mcd is "millicandela" the brightness value or luminosity. Link to comment
Xavier Posted December 23, 2002 Share Posted December 23, 2002 LEDs are in effect resistors themselves.. the resistance across the filament heats it and produces light... a resistor will help with surges that might otherwise burn the LED out. If your power supply is regulated, you're probably ok.. What I did was similar to what all of you have done, except that instead of cutting my AC adapter and hardwiring it, I purchased a the RS adapter with changable plugs. I found a matching plug to interface with the AC adapter's plug, then soldered the LED to that matching interface so it could easily be removed and put a different LED or replace a burned out one. I also purchased a snap in unit.. it's not made specifically for the LED (the kind in a plastic housing) I purchased so I also got some variable sized rubber gromets. The LED fit through the gromet at it's far end (away from the LED), then forced the rubber gromet into the snap in, leaving the head of the LED to poke through the other end of the snap in... I then used some sealant to secure the LED into place.. Ok.. I realize that probably made no sense.. I think santa is bringing me a digicam.. I'll take pics.... Link to comment
JD2003 Posted December 25, 2002 Share Posted December 25, 2002 LED's are not resistors. They are diodes, hence the name Light Emitting Diode (LED). They act like a short when you apply the proper voltage to them or an open circuit when you dont. You need a resistor when you use them. If you look at the LED specification, it will tell you how many volts and how much current is needed. Resistance=Voltage/Current If you do not put a resistor on the LED, you are probably overstressing the device if your power supply has parameters greater than the LED's need. This can lead to the device being very hot, having a short life, or breaking. Here is an example. Power Supply = 5V, 1.5A LED = 3V, 200mA (looking at formula above) Resistance = 5V/200mA Resistance = 25 Ohms ok so you need to put a 25 Ohm resistor in series with the LED. The power supply is 2V more than the LED need, but you dont need to worry about this because the resistor will take care of it. + ----LED-----Resistor----- - Now if we want to add more LED's we need to see how much current our power supply can provide. It can provide 1.5A and we need 200 mA for each LED. So we can have 7 LED's with this power supply. Each LED has to have a 25 Ohm resistor wired in series with it. And all 7 of these have to be wired in Parallel. + ----LED-----Resistor----- - + ----LED-----Resistor----- - + ----LED-----Resistor----- - + ----LED-----Resistor----- - + ----LED-----Resistor----- - + ----LED-----Resistor----- - + ----LED-----Resistor----- - Hope this help... although it might be a bit confusing Link to comment
Chamkeeper Posted December 25, 2002 Share Posted December 25, 2002 One resistor, LOTS of LEDs, pending the voltage drop per, same effect. Link to comment
JD2003 Posted December 26, 2002 Share Posted December 26, 2002 you could do that... but you need to have a higher wattage resistor if you do that.. I forgot to mention in the earlier message that you need to put the right wattage resistor also. Power = (Current)*(Current)*(Resistance) Link to comment
glazer Posted December 26, 2002 Share Posted December 26, 2002 Hmmm, had me, lost me, had me, lost.... I think I'm right back where I started... NO CLUE!....lol This is what I decided... what I got works and it's bright. Since the power pack I bought was/is a universal variable output power supply meant to replace the power supply on everything from cordless phones and Walkman's to electro vibrating objects de luv.... I am going to assume the little white box putting out the juice has a little tiny brain and will decide what my little tiny lights need to work properly... could happen, um right? Link to comment
JD2003 Posted December 26, 2002 Share Posted December 26, 2002 glazer, if your supply is 5V and your LED is rated for 5V then you wont have a problem. The main problem occurs when the Voltage of your supply is greater than what your LED needs. Thats when you need the resistor. Also if you are going to put more than one LED, make sure your power supply can handle it. Link to comment
Xavier Posted December 26, 2002 Share Posted December 26, 2002 Sorry JD.. my electronics is a bit rusty.. I was saying "in effect" because the resistance across the diode heats up causing the light (I believe.. I could be wrong.. it's been known to happen before)... I think I need to add a disclaimer to my sig.. heh heh Link to comment
JD2003 Posted December 26, 2002 Share Posted December 26, 2002 hey Xavier, everything has some resistive properties. Wire has resistance to it, but its very small. The LED gets hot because of its internal resistance. The reason why it lights up is a bit different. Here is the super short explanation. You have 2 energy bands, one is the conduction band and one is the valence band. When you apply a voltage, electrons from the conduction band jump to the valence band and emit a photon. The photon is light. And heat makes the electrons jump from the valence to the conduction band. Its kinda neat how it works, but it can give you a headache. trust me I know you should see the formulas behind this type of stuff... they are sick... hope this helps. JD Link to comment
Xavier Posted December 26, 2002 Share Posted December 26, 2002 I knew I got into embedded software for a reason.. so I wouldn't have to remember all the formulas! I took a digital electronics class back in college.. I've seen the formulas.. my big gray electronics handbook has plenty of them to make my eyes swivel into the back of my head... still an interesting topic.. I just wish there was a user group of people in my area that did it as a hobby as I do.. I learn much more from hands on then I do reading through books... Link to comment
Nishant3789 Posted December 30, 2002 Author Share Posted December 30, 2002 here tiz though its a real ######ty pic sry... u get the idea though ill try and post a pic of it over my new bsp nishant http://www.nano-reef.com/forums/showthread...p?threadid=6362 Link to comment
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