How many SMD 5630 LEDs can I power with 12V 1A power supply?

Question

I am new to this and have what is probably a newbie question.

I am using SMD 5630 LEDs from a strip that I am cutting off and wiring each LED individually. They will be wired in parallel and I am trying to understand how many I can power with a 12V 1A power supply. (Edit: The power supply converts to DC current.)

From the specifications I found each LED requires 3.6V at 50 mA and using an Ohm's calculator I found I need 22 ohm resistors. I just don't understand how to figure out the maximum number that I can support. Could someone explain, speaking slowly and using small words? :)

Answer 1

Adding to Passerby's answer: Replicate what's on the strip. It wastes the least current. The strip is made up of repeating circuits as shown below.

^{simulate this circuit – Schematic created using CircuitLab}

You should do the same. Polarity of LEDs matters. The resistors can go anywhere in the series circuit - they're probably evenly spaced on the strip to spread the heat.

Answer 2

IF the picture on the Amazon page is accurate to what you have, each segment has 2 27Ω resistors in series with 3 leds.

Using Ohm's law I = V/R to find out the current, Assuming 3V to 3.6V Forward Voltage drop on each led, that means the current at 12V is between

(12V Source Voltage - (3 Leds * 3.0V)) / 54 Ohms =  0.055 Amps (55 mA)

and

(12V Source Voltage - (3 Leds * 3.6V)) / 54 Ohms =  0.022 Amps (22 mA)

Since current is shared in series, this means each chip on that strip is only 22 to 55 mA.

So they are no where near your believed 150mA or 1/2 Watt.

To get the correct current, as far as the leds you have go, cut a single segment off, and using a ammeter or multimeter in current mode, measure the amperage of that single segment. That will tell you what it is using on the strip. Then I would adjust at least 10% down for a longer life. If you can't measure current, then measure the voltage across one of the resistors. Using Ohm's Law as above, take that voltage and divide by that resistance for the current flowing through it. That's what the LED should be using.

Update: It was suggested that the resistors are in parallel, and that the normal 5630 leds take 150 mA @ 3.4V. That may be true.

(12V Source Voltage - (3 Leds * 3.4V)) / 13.5 Ohms =  0.150 Amps (150 mA)

Only way to be sure would be to trace the circuit and measure the current or voltages with a multimeter.

Answer 3

I have a strip of 18 5630 smd leds and by test meter it draws 246 ma when powered by 12 v. dc power supply. if you divide that by 18 it comes out to 13.666666 ma for each led.

Answer 4

i run them each on 6.7 volts (6.2v nominal) 18mA. if you push them to 22mA you'll need some googles. the whole led strips are less than 120mA each. 80mA may be too dim but stable for a single regulation for each line. with proper line regulation you can reach 180mA fine at 26 or 27 volts...
Thus. if it ain't a special 12V package it may be two each 12v line but not precisely shiny because of lower voltage exitation...