LED Light Strips

[MapleLeafFarmer]

Clueless on some LED lights I was given. I am wondering how many watts at 12v 5m long light strip would need?

I was given a couple of boxes of LED's light strips in 5m and 50m rolls. I was told probably 300 rolls in total haven't counted them yet. No UL or other ratings.... they are Chinese meant for sale to chinese market ended up here in a container that wasn't supposed to get here. What I can see stamped on these rolls is:

Box 1: 5m light strips, EPISTAR LEDS, IP68 waterproofing, 12v, what I believe are resisters marked as "151" 1 resister for each light module , 18 LED's per foot. various colours like white/red/blue/green/etc...

Box 2: same as Box 1 but resistors stamped "101"

Box 3: 5m light strips, SAMSUNG LEDS, IP65 waterproofing, 12v, what I believe are resisters marked as "331" 1 for each light module , 18 LED's per foot. various colours like white/red/blue/green/etc...

Box 4: same as box 3 but resistors stamped "390"

and a whole bunch or RGD led's I havent got too yet.

Thinking the resistor number refers to colour output?

really wondering how many watts each say 5m roll would need?


any wisdom appreciated.

thanks and they look like this in rolls

 

[sagor]

Resistor values determine the current flow through the LEDs. Some LEDs may be single and have a higher resistor value. Some LED strips may put 2 or 3 LEDs in series and thus the resistor will be a smaller value.
Each LED has a voltage drop across it. Some as low as 1.8V, like red LEDs. Others can be over 3.0V, like blue or some white LEDs. Putting LEDs in series sets a certain voltage drop, and the remaining value (12V-voltage drop) is used to calculate the resistor value.
When making a 12V string, manufacturers figure out an economical combination of LEDs in series and add the appropriate resistor to limit the current through the LED(s) to a certain value.
You can calculate the total wattage by measuring the current draw at 12V for a certain length (like 1M). Most strings then replicate the same circuit as you roll out more of the string.

 

[MapleLeafFarmer]

thanks.... there is 1 resistor between every light module so 18 resistors and 18 light modules per foot.
Also each light module has 6 solder points to them (3 on each side).

 

[GSD-Keegan]

Just for what it’s worth. I installed similar strips in a gazebo, housing a hot tub. Weather resistant apparently. However they didn’t last long.

 

[sagor]

Looking at the picture, between the scissor cut marks there are 3 LEDs and one resistor. That suggests the three LEDs are in series. Depending on the color, the voltage drops could be 3x1.8V = 5.4V for red, all the way up to 3 x 3.1V = 9.3V for some blue or white LEDs.
The resistor would be sized to limit current to about 10mA (give or take some - could be up to 20mA). At 20mA, the red LED resistor would need to drop 12V-5.4V = 6.6V. That would mean a 330 ohm resistor (331).
For 3 blue LED in series, the resistor would need to handle 12V-9.3V = 2.7V. At 20mA, that would require a resistor of about 130 ohms (131). It could even be 101 (100 ohms) or 151 (150 ohms) in some cases.
So, it all depends on the LED strip design and the color of the LEDs.

 

[NHSleddog]

I was awarded a patent on an Modular Self Adhesive LED light strip in the early 90's. Unfortunately, it was an idea about 15 years before its time.

 

[GreensvilleJay]

From your picture ,in a 'segment'(between the 'cut heres), there's 3 LEDs in series with a 151 resistor. 151 means 150 ohms (1,5,and # of 0s)
white LEDs need 3.2 volts to turn on, so 3x 3.2=9.6, 12-9.6=2.4. 2.4/150=.016 amps.
So 16 millamps of current to turn on a 'segment' of 3 white LEDS.
with 18 LEDS per foot, 18/3=6, so 6 segments, 6 * 16= 96ma, call it 100ma for easy math...
A 1 Amp power supply(wallwart) should run 10 feet of that LED strip. 1 amp = 1000ma.
10 feet is about 3 meters...so a 1.5A power supply should run a 5M strip.
You'll find 12V2A power supplies real common... 24 watts.
101 = 100 ohms
331 = 330 ohms
390 = 39 ohms

 

[MapleLeafFarmer]

From your picture ,in a 'segment'(between the 'cut heres), there's 3 LEDs in series with a 151 resistor. 151 means 150 ohms (1,5,and # of 0s)
white LEDs need 3.2 volts to turn on, so 3x 3.2=9.6, 12-9.6=2.4. 2.4/150=.016 amps.
So 16 millamps of current to turn on a 'segment' of 3 white LEDS.
with 18 LEDS per foot, 18/3=6, so 6 segments, 6 * 16= 96ma, call it 100ma for easy math...
A 1 Amp power supply(wallwart) should run 10 feet of that LED strip. 1 amp = 1000ma.
10 feet is about 3 meters...so a 1.5A power supply should run a 5M strip.
You'll find 12V2A power supplies real common... 24 watts.
101 = 100 ohms
331 = 330 ohms
390 = 39 ohms

thanks for the info... fyi the pictures was one cut from internet.
the ones I have have 1 resistor per light module. Would this change the calculations you made?

 

[GreensvilleJay]

no.
the 'reel of lights', is made of 'segments' consisting of LEDS and a resistor, You cut (where the scissiors icon is) to make a 'strip of light',any length, that is powered from 12 volts.
The resistor value is based on colour of LEDs and qty of them,but generally speaking, each 'segment' will draw 15 millamps ,though you should measure the actual current drawn. The longer the strip(# of segments) ,the more current will be needed.
I used LEDs to monitor TTY(Teletype) current loops 4 decade ago...20 millamp was a standard then.