Help appreciated! Is the attached voltage drop diagram correct? I need to convert a 16-12v battery for use with a 4v LED lamp. I've bought an led desk-lamp which was sold with a DC supply rated as follows:
4v 0.75A 3W.
I want to use it with a 16v battery (fully charged) whose voltage drops eg down to 12v over a few hours. IE, do I need to buy 1x16 ohm and 1 x 5.33 ohm resistor?
Thanks so much!
Typically you would drive the LED with a circuit like so:
where you set the voltage across the diode to 4 Volts, and set the current in the circuit to 750 mA. If you perform the calculations, the resistor will be 16 ohms. The issue here, as Don stated, is that a large portion of your power will be consumed by the 16 ohm resistor (P = I^2 * R = 9 W). If you are fine with that, then you're done. If you want the battery to last longer you'll require a different solution.
Typically you would drive the LED with a circuit like so:
where you set the voltage across the diode to 4 Volts, and set the current in the circuit to 750 mA. If you perform the calculations, the resistor will be 16 ohms. The issue here, as Don stated, is that a large portion of your power will be consumed by the 16 ohm resistor (P = I^2 * R = 9 W). If you are fine with that, then you're done. If you want the battery to last longer you'll require a different solution.
