2021年4月6日 · LEDs are nonlinear devices -- their current vs. voltage curve is exponential with voltage. In practical terms, it means that essentially no current flows at low voltages, and then the current very rapidly rises. In the case of your LED, that "low voltage" is around 1.6V. If you look at the datasheet, figure 2, you'll see this.

2015年1月30日 · The purpose of the series resistor is to throttle the current through the LED. Forward voltage of the LED goes into the in calculation of the current limiting resistor. $$ R = \frac{V_{cc} - V_f}{I_f} $$ There is nothing fundamentally wrong with using a higher voltage if you size the current limiting resistor appropriately for the voltage.

2022年5月5日 · The curve is for the LED alone. The voltage across your resistor will be the supply voltage from your CR1220 minus the LED's voltage. So the LED affects the current flowing through the circuit. But the current through the circuit also affects the voltage across the LED.

2011年3月3日 · Typically, the forward voltage of an LED is about 1.8–3.3 volts; it varies by the color of the LED. A red LED typically drops 1.8 volts, but voltage drop normally rises as the light frequency increases, so a blue LED may drop around 3.3 volts. LED forward voltage quick reference. IR LED drops about 1.5V; Red: ~2V; Amber: ~2V; Yellow: ~2V ...

2018年1月10日 · the voltage of the LED is multiplied by the number of series = drive voltage. the driving current for each series of LED should be within 20mA. if the LED light string is parallel, the drive current =20ma is multiplied by the number of parallel connections. Considering the safety of LED, the current is better than the calculated current.

If a resistor or a CC source drives a LED, the forward voltage will appear automatically in accord with LED's inherent I-V diagram, so nobody really cares much about what it is. More, with 20-30 mA and around 3.3 V, the heat dissipation of this LED will be about 100 mW, which will cause substantial rise of die temperature given the tiny plastic ...

2021年6月28日 · Some LED datasheets will have a current/voltage chart, some won't. With the typical mixed grab bag stuff hobbyists get from Amazon or e-Bay or wherever, you won't have a current/voltage chart. You can make them yourself if you have (or make) a small I/V plotter.

2009年12月23日 · Non-super bright LEDs are often rated for 20mA, so select the series resistor accordingly. How do you do this for a LED whose specs are missing? Place a 100\$\Omega\$ test resistor in series with the LED and vary the voltage until the voltage drop over the resistor is 2V (\$\frac{2V}{100\Omega}=20mA\$). Now measure the voltage across the LED.

2015年4月7日 · The voltage across any forward-biased LED (any diode, really) will be governed by the diode, and will only vary slightly with current. Look on the LED's data sheet for the recommended operating current, or, failing that, the Maximum Recommended current. If you can only find a Maximum Recommended current, operate the LED at 80% or less of the ...

2015年6月1日 · Connect the LED to the meter leads, verifying correct polarity; Meter will indicate forward drop (usually 1V-3V for most LEDs.) Note that the LED may glow. Now that you have the LED's forward voltage drop you can figure out how much voltage everything else in the "chain" will need to drop. For very simple circuits it may just be a limiting ...