I have a set of Christmas lights that have a little box on the end that has 7 settings. What i want to do is cut out that box and put an on-off switch with the right resistors or whatever it needs ,so that i can run 120v.I want to use this for a fish tank light.
what do i need for led cord....
- Thread starter daves66nova
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120V from an outlet is AC. So you need diodes to rectify that.
Then you'll need to calculate resistors based on the number of LED's.
And the LED current draw.
And how the LED's are wired.
So, please, if you're gonna say "or whatever it needs"; don't play with 120v near a fish tank. It sounds like a disaster waiting to happen and in no way can someone writeup a reply here that will in any way educate you completely enough to accomplish this.
Then you'll need to calculate resistors based on the number of LED's.
And the LED current draw.
And how the LED's are wired.
So, please, if you're gonna say "or whatever it needs"; don't play with 120v near a fish tank. It sounds like a disaster waiting to happen and in no way can someone writeup a reply here that will in any way educate you completely enough to accomplish this.
I already have plenty of 120v items in or around my fish tank.I say "or whatever it needs" because i don't know exactly what i need,that's why I'm asking here,because I DON'T KNOW. A disaster? Like, the leds burn out or not work altogether? Hardly a disaster.
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What voltage are the LEDs rated for? Get a small transformer to step the 120V down to an appropriate voltage, then add a rectifier to convert it to DC.
A converter plug used for small electronics will have both of these built in:
A converter plug used for small electronics will have both of these built in:
This will not end well. Unless by well you mean electrocution or house fire.
Originally Posted By: daves66nova
I have a set of Christmas lights that have a little box on the end that has 7 settings. What i want to do is cut out that box and put an on-off switch with the right resistors or whatever it needs ,so that i can run 120v.I want to use this for a fish tank light.
The fish and plants are just gonna love that . . .
The CRI/temp on led lighting is still awful at best IMO. If this is for a more serious FW aquarium (this just can't be for a reef tank), I'd stick with traditional florescent lighting which has proven color temperature and high CRI ratings for the job.
. . . unless this is what my wife likes to call a "tacky tank", complete with bubbling treasure chest on hot pink gravel for the goldfish. They have their place, too, I suppose.
I have a set of Christmas lights that have a little box on the end that has 7 settings. What i want to do is cut out that box and put an on-off switch with the right resistors or whatever it needs ,so that i can run 120v.I want to use this for a fish tank light.
The fish and plants are just gonna love that . . .
The CRI/temp on led lighting is still awful at best IMO. If this is for a more serious FW aquarium (this just can't be for a reef tank), I'd stick with traditional florescent lighting which has proven color temperature and high CRI ratings for the job.
. . . unless this is what my wife likes to call a "tacky tank", complete with bubbling treasure chest on hot pink gravel for the goldfish. They have their place, too, I suppose.
No, no bubbles, no skeleton,just crushed coral and Electric Yellows and Cobalt Blues.These have a 6000K rating.
LED - light emitting diode
The way it works in a nut shell, is that they have low resistance, but a voltage drop (threshold voltage) when run in the correct direction. If you plug it in the opposite way, it will not turn on.
That box in the end has a lot of stuff in side, most likely a power supply to drive the LEDs, and some resistors to keep the current in the right range. LED power draw and the brightness is based on how much current you supply it, and since it is not a resistor, you cannot just divide the voltage over its resistance and calculate how much current it is drawing.
As a back of the envelope calculation, when I was playing with LED I usually use something like a 1.2V drop per LED in series as a reference. Then I subtract the voltage from the power supply voltage (i.e. a 12V power supply to drive 5 LED will be 12V - 5 * 1.2V = 6V), and divide that difference by the resistors valve to keep it at around 20mA (reference LED has full brightness at 20mA and will last a couple decade, 10mA will reduce brightness and last longer, more than 20mA will burn it out without any extra brightness, etc), so in this example the 6V / 20mA = 300 Ohm resistor in series.
Please remember that it all depends on how many LED they wire in series, and the actual spec of the LED they use (may not be 1.2V and may not be 20mA). When in doubt, use a higher supply voltage and larger resistor in series to minimize the affect of the threshold voltage's influence in case it is off, and when in doubt, bigger resistor to limit the amount of current to below 20mA for safety. i.e. If I use 120V to drive 50 LED in series (60V) with 3k Ohm resistor will be safer than using 90V to drive 50 LED in series (60V) with 1.5k Ohm resistor. If the LED voltage drop I use was off by 50% (i.e. 30V drop only), the amount of current difference would be (120V - 30V) / 3k = 30mA (10mA over) for 120V supply vs (90V - 30V) / 1.5k = 40mA (20mA over).
Too much trouble if you just want to save space. It would be easier if you just cut the wire and extend it, and relocate the box elsewhere.
The way it works in a nut shell, is that they have low resistance, but a voltage drop (threshold voltage) when run in the correct direction. If you plug it in the opposite way, it will not turn on.
That box in the end has a lot of stuff in side, most likely a power supply to drive the LEDs, and some resistors to keep the current in the right range. LED power draw and the brightness is based on how much current you supply it, and since it is not a resistor, you cannot just divide the voltage over its resistance and calculate how much current it is drawing.
As a back of the envelope calculation, when I was playing with LED I usually use something like a 1.2V drop per LED in series as a reference. Then I subtract the voltage from the power supply voltage (i.e. a 12V power supply to drive 5 LED will be 12V - 5 * 1.2V = 6V), and divide that difference by the resistors valve to keep it at around 20mA (reference LED has full brightness at 20mA and will last a couple decade, 10mA will reduce brightness and last longer, more than 20mA will burn it out without any extra brightness, etc), so in this example the 6V / 20mA = 300 Ohm resistor in series.
Please remember that it all depends on how many LED they wire in series, and the actual spec of the LED they use (may not be 1.2V and may not be 20mA). When in doubt, use a higher supply voltage and larger resistor in series to minimize the affect of the threshold voltage's influence in case it is off, and when in doubt, bigger resistor to limit the amount of current to below 20mA for safety. i.e. If I use 120V to drive 50 LED in series (60V) with 3k Ohm resistor will be safer than using 90V to drive 50 LED in series (60V) with 1.5k Ohm resistor. If the LED voltage drop I use was off by 50% (i.e. 30V drop only), the amount of current difference would be (120V - 30V) / 3k = 30mA (10mA over) for 120V supply vs (90V - 30V) / 1.5k = 40mA (20mA over).
Too much trouble if you just want to save space. It would be easier if you just cut the wire and extend it, and relocate the box elsewhere.
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Just realize it is about the on / off duration of the Christmas light. In that case, it might be cheaper to do the following:
1) get a volt / current meter
2) cut the wire and put it in parallel with the volt meter (AC) setting, to see what is the voltage of the output when the LEDs are powered on.
3) put the current meter in series and see what is the output when the LEDs are powered on.
4) buy an AC power supply and put it in series with resistor(s) so the output is identical or close to what you were measuring earlier.
5) if you don't mind only 1/2 of the LEDs are turned on, you can use a DC power supply.
1) get a volt / current meter
2) cut the wire and put it in parallel with the volt meter (AC) setting, to see what is the voltage of the output when the LEDs are powered on.
3) put the current meter in series and see what is the output when the LEDs are powered on.
4) buy an AC power supply and put it in series with resistor(s) so the output is identical or close to what you were measuring earlier.
5) if you don't mind only 1/2 of the LEDs are turned on, you can use a DC power supply.
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