I just put 100, 3.0 - 3.2 led's (2-wire) on a buck converter, step down voltage regulator. I supplied the tiny converter with a 120VAC wall converter that puts out 12VDC.
The little converter says 4-38 DCV input and output 1.25-36 DCV stepdown power. I began turning up the voltage slowly until forward voltage read "3.2 volts" VDC coming out the business end of the little converter. Voila! All of the LED's lit up!
Is that all there was to it? Did it right? Don't need any resistors?
Going to line my new deck with tem.
How many LED's could I have used in one long line?
Can I hook another little converter to this same supply and run another string?
"NEW" here...... where do I find an answer to this?
Can I run them all? Is there a limit?
Is that all there was to it? Did it right? Don't need any resistors?
No, you need resistors.
LEDs are current operated, they need resistors to control the current, they don't do it themselves. A tiny change in voltage is enough to go from no current and the LED off to too much current and the LED goes pop.
No, because LEDs need stable current flow, and their forward voltage varies between devices and with temperature.
You either use a constant current supply into a series string of LEDs, or a constant voltage supply and a current limiting resistor to power a string. The resistor needs to handle about 15% or more of the voltage of the supply for stable operation.
If you power LEDs from a constant voltage source without any resistance they can be set to a particular brightness and current, but there's no guarantee they will stay at that level over time or as their temperature changes. You can get thermal runaway as the higher temperature leads to more current, and thus more self-heating.
Yes it will work. I have found it is much less expensive to replace resistors then LEDs which will be the case with your circuit. You can also drive them with a constant current source, these are relative inexpensive but you need to do some research before using them, You can reduce your number of resistors by placing the LEDs in series and these series strings can go across a power supply. Simply add up the Vf (forward voltage) and when you put enough in series so you are just a little below the power supply voltage. use the LED resistor calculator at: LED Resistor Calculator but remember when you use strings the Vf voltages are added, the current remains the same. Watch the power dissipation which the calculator will give you and do not exceed 50% of your resistor rating. I like to stay in the low hundreds range. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil