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Step 3Selecting the power supply
This step helps you figure out:
- what power supply to use
- how many LED's to use
How big a light can you make? It all depends on your power supply. you need a power supply between 12V and 25V DC, and 2 amps minimum. more amps lets you use more LED's, and the high-end of the voltage range will let you use more LED's and be a bit more efficient also.
Old laptop power supplies are the best because they are usually between 18V and 24V, and are small, efficient and fan-less. you can usually extract a boxed power supply from most larger electronic equipment such as desktop computers, these will at least get you 12V with lots of current. check the sticker on your power supply to see what its specifications are.
Voltage: this determines the number of LED's in series you will need. we will put the LED's in series strings so that each series string uses close to the power supply voltage when running at full power.
Current: this determines the number of parallel strings of LED's you will have. you need 3 minimum: one each for Red, Green and Blue. Count 600mA for 1-watt LED's and 1200mA for 3-watt LED's, so that means the minimum current for your power supply is 3 x 600mA or 1.8 Amp. If you have more than double that, you can put more parallel strings of each color (but you don't have to if you want a smaller light). you'll run your LED's a bit less than this, but you need some "spare" capacity to avoid burning out the power supply.
ok, so how large will our series LED strings be? start with these figures (calculated using the LED forward drop, plus a 1.5 volt overhead):
12-volt power supply, luxeon-1 up to 300mA LED current, or lux-3 up to 600mA
4 x red, 3 x green, 3 x blue
12-volt power supply, lux-1 up to 600mA
3 x red, 3 x green, 3 x blue
18-volt power supply, lux-1 up to 500mA
5 x red, 5 x green, 5 x blue
20-volt power supply, lux-1 up to 500mA
6 x red, 5 x green, 5 x blue
20-volt power supply, lux-3 up to 700mA
6 x red, 5 x green, 5 x blue
24-volt power supply, lux-1 up to 550mA
7 x red, 6 x green, 6 x blue
24-volt power supply, lux-3 up to 800mA
7 x red, 6 x green, 6 x blue
so: most laptop power supplies are between 18V and 24V, and between 2A and 3A. This will let you make a light with 12-20 LED's (using strings of 4, 5, 6 or 7 LED's). if you have a high-current supply, you can put strings in parallel also.
- if you are looking for a power supply specially for this project, ideal would be 24-25V supply with 3-4A per set of LED's. ie, 3-4A for 18 LED's, 6-8A for 36 LED's, etc. As designed the controller can handle up to 15A maximum.
- the reason to prefer a supply between 20-25V that the controller will be a bit more efficient than with a 12V supply, and the maximum number of LED's you can power will be more. however if you want a smaller light, a 12V supply will be just fine. you can't use more than 25V, that is the limit for the regulator chips we are using.
- what power supply to use
- how many LED's to use
How big a light can you make? It all depends on your power supply. you need a power supply between 12V and 25V DC, and 2 amps minimum. more amps lets you use more LED's, and the high-end of the voltage range will let you use more LED's and be a bit more efficient also.
Old laptop power supplies are the best because they are usually between 18V and 24V, and are small, efficient and fan-less. you can usually extract a boxed power supply from most larger electronic equipment such as desktop computers, these will at least get you 12V with lots of current. check the sticker on your power supply to see what its specifications are.
Voltage: this determines the number of LED's in series you will need. we will put the LED's in series strings so that each series string uses close to the power supply voltage when running at full power.
Current: this determines the number of parallel strings of LED's you will have. you need 3 minimum: one each for Red, Green and Blue. Count 600mA for 1-watt LED's and 1200mA for 3-watt LED's, so that means the minimum current for your power supply is 3 x 600mA or 1.8 Amp. If you have more than double that, you can put more parallel strings of each color (but you don't have to if you want a smaller light). you'll run your LED's a bit less than this, but you need some "spare" capacity to avoid burning out the power supply.
ok, so how large will our series LED strings be? start with these figures (calculated using the LED forward drop, plus a 1.5 volt overhead):
12-volt power supply, luxeon-1 up to 300mA LED current, or lux-3 up to 600mA
4 x red, 3 x green, 3 x blue
12-volt power supply, lux-1 up to 600mA
3 x red, 3 x green, 3 x blue
18-volt power supply, lux-1 up to 500mA
5 x red, 5 x green, 5 x blue
20-volt power supply, lux-1 up to 500mA
6 x red, 5 x green, 5 x blue
20-volt power supply, lux-3 up to 700mA
6 x red, 5 x green, 5 x blue
24-volt power supply, lux-1 up to 550mA
7 x red, 6 x green, 6 x blue
24-volt power supply, lux-3 up to 800mA
7 x red, 6 x green, 6 x blue
so: most laptop power supplies are between 18V and 24V, and between 2A and 3A. This will let you make a light with 12-20 LED's (using strings of 4, 5, 6 or 7 LED's). if you have a high-current supply, you can put strings in parallel also.
- if you are looking for a power supply specially for this project, ideal would be 24-25V supply with 3-4A per set of LED's. ie, 3-4A for 18 LED's, 6-8A for 36 LED's, etc. As designed the controller can handle up to 15A maximum.
- the reason to prefer a supply between 20-25V that the controller will be a bit more efficient than with a 12V supply, and the maximum number of LED's you can power will be more. however if you want a smaller light, a 12V supply will be just fine. you can't use more than 25V, that is the limit for the regulator chips we are using.
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Dec 27, 2008. 11:25 AMpyro_fan_ryan
says:
how manie amps is 200 mA?
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Jan 11, 2009. 5:20 AMDerin
says:
200mA=0.2A
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