I am trying to come to terms with LEDs and power supplies.
Goals:
To learn how to build and to power LED arrays & do it.
To learn about the relationship between power supplies and LED power consumption.
To learn how to build my own power supply.
There is an Wikihow article on turning a PC power supply into a lab supply here:
How to Convert a Computer ATX Power Supply to a Lab Power Supply (with video) - wikiHow
I have several low voltage Track Lighting transformers left over from a renovation. The produce 24VAC. I think I’d rather make my own but the temptation to use these is high.
I'm still trying to figure out how to do what I want.
-============================================
Powering LEDs
Take this:
R = (VS - VL) / I
where
R = the resistor
VS is the cumulative voltage demand of the LEDS in series
I = the LED draw in Millliamps (mA)
Example:
A series of 6 LEDs (assume 2 VDC for each) I can take a 120VAC line voltage rectify it to DC and end up with: 120 - 6 / 0.02 = 5850 Ohms resistance
Does that make sense? I need a resister of 5850 Ohms??
I just know I am only a quarter right and there’s more I need to know.
And I see different way of connecting a resistor to an LED.
Some people are putting the resistor in the Negative terminal and others on the Positive.
Examples:
**broken link removed**
http://www.theledlight.com/img-tech/series101.jpg
Is one more correct than the other?
Does it matter which terminal is used for the resistor?
-=========================================================
Then on to the power supply.
If I understand what I’ve read correctly, I need no less than the voltage the LEDS will draw down. So a 120VDC (or AC) line will not drive more than 51 LEDs?
Does that make sense?
I can only drive 51 Two Volt LEDs on a 120 Volt supply line?
That makes no sense.
I've seen systems where way more than 50 LEDS are running in a plug and play bank of hundreds of LEDs and the thing is sold to plug into a 120 VAC line. There isn’t the physical space in them for banks of capacitors. So I’m missing something.
What am I doing wrong??
This tells me that the statement about matching power supply to LED consumption is error - - - or at least how I have understood it is error. :
This is 72 white (2 volt) LEDs on a board
**broken link removed**
The Description says:
This assembled and tested unit 72-880nm LEDs with a 50 degree viewing angle. The LEDs in this unit are capable of drawing 100mA. each. The Bigger IR ILLUMINATOR kit is designed to operate between 12 and 13.8Vdc, with maximum efficiency at 13.2Vdc. IR Illuminator draws between 600-800mA. Units can be daisy chained. At 24 feet, the beam is approximately 8 feet in diameter. PC board measures 3.7"x1.95".
They says it's tested with this itty bitty $4.00 power supply
**broken link removed**
That tells me I haven’t yet got a handle on LED power consumption or how to feed them.
Input would be appreciated.
Goals:
To learn how to build and to power LED arrays & do it.
To learn about the relationship between power supplies and LED power consumption.
To learn how to build my own power supply.
There is an Wikihow article on turning a PC power supply into a lab supply here:
How to Convert a Computer ATX Power Supply to a Lab Power Supply (with video) - wikiHow
I have several low voltage Track Lighting transformers left over from a renovation. The produce 24VAC. I think I’d rather make my own but the temptation to use these is high.
I'm still trying to figure out how to do what I want.
-============================================
Powering LEDs
Take this:
R = (VS - VL) / I
where
R = the resistor
VS is the cumulative voltage demand of the LEDS in series
I = the LED draw in Millliamps (mA)
Example:
A series of 6 LEDs (assume 2 VDC for each) I can take a 120VAC line voltage rectify it to DC and end up with: 120 - 6 / 0.02 = 5850 Ohms resistance
Does that make sense? I need a resister of 5850 Ohms??
I just know I am only a quarter right and there’s more I need to know.
And I see different way of connecting a resistor to an LED.
Some people are putting the resistor in the Negative terminal and others on the Positive.
Examples:
**broken link removed**
http://www.theledlight.com/img-tech/series101.jpg
Is one more correct than the other?
Does it matter which terminal is used for the resistor?
-=========================================================
Then on to the power supply.
If I understand what I’ve read correctly, I need no less than the voltage the LEDS will draw down. So a 120VDC (or AC) line will not drive more than 51 LEDs?
Does that make sense?
I can only drive 51 Two Volt LEDs on a 120 Volt supply line?
That makes no sense.
I've seen systems where way more than 50 LEDS are running in a plug and play bank of hundreds of LEDs and the thing is sold to plug into a 120 VAC line. There isn’t the physical space in them for banks of capacitors. So I’m missing something.
What am I doing wrong??
This tells me that the statement about matching power supply to LED consumption is error - - - or at least how I have understood it is error. :
This is 72 white (2 volt) LEDs on a board
**broken link removed**
The Description says:
This assembled and tested unit 72-880nm LEDs with a 50 degree viewing angle. The LEDs in this unit are capable of drawing 100mA. each. The Bigger IR ILLUMINATOR kit is designed to operate between 12 and 13.8Vdc, with maximum efficiency at 13.2Vdc. IR Illuminator draws between 600-800mA. Units can be daisy chained. At 24 feet, the beam is approximately 8 feet in diameter. PC board measures 3.7"x1.95".
They says it's tested with this itty bitty $4.00 power supply
**broken link removed**
That tells me I haven’t yet got a handle on LED power consumption or how to feed them.
Input would be appreciated.