@jjm posted:There is a package offered on Amazon that includes LEDs and resistors. Would these work along with the diodes listed below?
LED & resistor Specs:
- Product Overview: 100 pcs LED Diodes + 100 pcs Resistors
- Product Features: Warm White Lights / 3mm Diffused Round Lens / White Lens
- Product Parameters: 29mm Long Lead / DC 3.0V-3.2V (IF=20mA) / 0.06 Watts / 2pin / DIP LEDs
- Product Parameters: Luminance Brighter Up To +20% / Wavelength 1200K-3500K / 120° Viewing Angle / Single LED Diodes Wight: 0.16g
- Accessories: 100pcs 430ohm (For DC 6-12V) 1/4 Watt Metal Film Resistors Include / ±1% Tolerance
Diodes: (Pack of 100 Pieces) Chanzon 1N4001 Rectifier Diode 1A 50V DO-41 (DO-204AL) Axial 4001 IN4001 1 Amp 50 Volt Electronic Silicon Doorbell Diodes
That all looks like it should work. Current will be just a little higher with a 430 ohm versus a 470 ohm, but not much. About 12.6 mA. And only about 0.07 watts for the resistor which is well below the 1/4 watt resistor rating. As you have noticed on Amazon, such parts, especially the Chinese ones you mentioned, hardly cost anything. With 20 mA rated LEDs, that should be fine. But I have some reliability problems with some of the cheap LEDs.
If you want to know how the "math" works. First, there will an approximate 3 volt drop across each LED and approximate 0.6 volt drop across the diode. With four LEDs and one diode that is a 12.6 volt drop total. Assuming an 18 volt supply, the voltage across the resistor is whatever voltage is left which is 18 V - 12.6 V = 5.4 V.
Current is from Ohms law arranged as I = E/R (current is voltage divided by resistance) and is 5.4 V / 430 ohm = 12.6 mA.
Power dissipated by the resistor will be I squared times R or 0.0126 amp x 0.0126 amp x 430 ohm = 0.068 watts, (Meaning it shouldn't be able to melt a plastic roof - but it is always good to temporarily connect a circuit idea together on the bench and test it first.)
