A very common power supply used in LED lamps is a little switchmode power supply that is designed to put out a current of around 300mA at between about 3V to 12V to drive 1 to 3 1W LEDs in series.
If you connect these supplies to standard LED tape with multiples of three LEDs in each section, then the power supply will drive whatever length of tape you connect to it, but the voltage will adjust down until the full 300mA is shared between all the LEDs.
This means that for a 5m roll of tape the current will be divided between 100 circuits of 3 LEDs giving just 3mA per circuit.
That's actually enough to run the tape brightly for visual effect, while ensuring it has a long lifespan due to being under-run.
There are a couple of caveats though.
If an LED goes short circuit then the voltage may be pulled down to the rest of the LEDs as it passes more than its share of the current.
If the tape breaks then the 300mA will be shared amongst the remaining LEDs, and for a very short section it could overdrive them.
There is no guarantee of proper mains isolation with these tiny switching power supplies. They are intended for closed lamps, so there is a risk that the LED tape could be referenced to the mains.
This was done purely as an experiment.
If you connect these supplies to standard LED tape with multiples of three LEDs in each section, then the power supply will drive whatever length of tape you connect to it, but the voltage will adjust down until the full 300mA is shared between all the LEDs.
This means that for a 5m roll of tape the current will be divided between 100 circuits of 3 LEDs giving just 3mA per circuit.
That's actually enough to run the tape brightly for visual effect, while ensuring it has a long lifespan due to being under-run.
There are a couple of caveats though.
If an LED goes short circuit then the voltage may be pulled down to the rest of the LEDs as it passes more than its share of the current.
If the tape breaks then the 300mA will be shared amongst the remaining LEDs, and for a very short section it could overdrive them.
There is no guarantee of proper mains isolation with these tiny switching power supplies. They are intended for closed lamps, so there is a risk that the LED tape could be referenced to the mains.
This was done purely as an experiment.
Hello Clive , please help me how do u calculate current load for 100 m triple LED and how much LED driver needed?
Why is it calculated as 0.48V rather than the measured 4.48V across 150 ohms?
Thanks for the GREAT VIDEO. I had been searching for something like that, for AGES! I have got LED lamps at my home, and very often they burnt out. They were pretty expensive to replace. However I had bought cheap LED strips from China that I wanted to put in the lamps instead of replacing the whole lamp. I wanted to find out if I could run the 12V LED strip, with the Constant Current Power Supply used originally in the LED Lamp. So apparently I can… Will try it now..
I've got RGB+W 12V 5m LED strip and as I counted:
1 segment = 10cm = R+W+G+W+B+W -> 6 x 5050 LEDs
5m = 50 segments = 300 LEDs
300 * 20mA * 12V = 72W (12V 6A)
Am I right?
But what if I just want to drive only for example RED and BLUE (using arduino)?
Does it mean that I need (2*50*20mA*12V) 24W (12V 2A)?
I was searching your channel to see if you did a video on ebay AC to DC power supplies. I was shocked to find this video because I actually used this setup to run some led's under my microwave. I used a 1M length (60 led's that I did have to cut down a bit. I think I shortened it by 4 or 5 led's). I was curious to the quality of the power supply and the safety of it.
Hey Thanks for the video, can you use a 12V DC controller with the downlights instead of the 300mA thingy?
Clive (or anyone) . . Can I run those led strips off an ATX (Pc) power supply on the 12v? I'm doing it already intact and they seem to like it, I'm just concerned about longevity . . Thanks.
I'm using 2x 5 meters led tape and more 40 centimeters of tape. A 12v 2A at the controller, and in each joint a little amplifier with One more power supply 12v 2A.
But, the lights are messing, only a few is working propelly.
Any suggestion? Any idea?
Note, all of them works fine alone, things get strange after the amplifier.
Very helpful thanks Clive
Hi! well great video but i hate the fact that it confused me even more. xD Did you say the LEDs are connected in parallelxD project involves a 5m Led strip rated at 20w per meter at 5v. what is the recommended power supply as far as the current is concerned.
Addictive videos……
Must ask, do you teach? If not then you really ought to consider doing so…
Where can I get a workbench quick connect like you have with blue, green and brown quick connectors? That is awesome and perfect for quick connect of line voltage. I like the way the lid snaps closed for safety.
I wired one of those boxes with an infared reciever up to a molex connector and plugged it straight into the 12V rail on my computer PSU. I have RPG LED tape inside my case now. Looks cool as hell!
warum geht das alles nur immer englich?