So I designed and have submitted for a patent on a lighting system. Now I'm trying to wire it. Only electricity I've ever touched is inside a car's dashboard and all splice and solder easy stuff.

Trying to make this work:
48V-1000Watt Power Supply
Each LED = 1W, VF (3.2-3.6vdc), IF (350mA)



So in the instance above I have wired 4 strings (15 led in series With 15ohm/.5w resistor on the NEG end) in parallel. This lights up and runs great. Out of the 5 plates(full units) that I made, 2 of them had resistors that burnt up within 10 seconds. The other 3 plates worked as planned with no issues.


Above is the simple wiring diagram i used to wire my first version. I recalculated and determined that I could add one additional LED to make an even 48v.

So my question is: why are the resistors burning? My supply is 48 V and my 15 LED in series at 3.2v equals 48V. I have some plates that require different wattage but always in increments of 15watts so I can always use the 48V power supply.

 

Your resistors are rated at 0.5 watt; 0.35A * 0.35A * 15Ω = 1.84 watts, that's why they're burning up. Use resistors with a higher wattage rating, preferably 3 watts or more.

Always do the math before plugging stuff in.

 

Look at the LED data sheets- the Vf is never 'exactly' any voltage, there is a range that will horrify you when you think of what it implies for your design.

Any decent LED lighting fixture must to be designed to accommodate this variation in Vf, otherwise many units will not work, the ones that do will have wildly varying current.

Large strings must be driven with enough voltage headroom to deal with this, if you are using a simple resistor, this means large current variation, or lots of wasted power.

Better to use a switching driver that provides constant current.

 

Your resistors are rated at 0.5 watt; 0.35A * 0.35A * 15Ω = 1.84 watts, that's why they're burning up. Use resistors with a higher wattage rating, preferably 3 watts or more.

Always do the math before plugging stuff in.

So according to my diagram what resistor should I put on each string of 15 LEDs? On the first positive side or the end negative side? And can you explain the math behind it?

 

So according to my diagram what resistor should I put on each string of 15 LEDs?

I would do what @Sensacell recommended: instead of a simple resistor to limit the current, use a proper LED driver chip that operates as a switching regulator. It's much more energy efficient, generates a lot less heat, and eliminates the problem of uncertain LED forward voltage drop.

On the first positive side or the end negative side?

There's no difference.

And can you explain the math behind it?

If you choose to use a resistor for current limiting, Google the phrase "calculating led series resistor". That will give you all the help you need.

 

So according to my diagram what resistor should I put on each string of 15 LEDs? On the first positive side or the end negative side? And can you explain the math behind it?

No amount of math is going to help you here.

You simply have too many LED's in series for a simple resistor at that input voltage.

If you do the math for the data sheet Vf extremes, the current will vary from say... zero, to way too much.
Zero current happens when the Vf's add up to MORE than the power supply voltage.

This scheme only works when the lions share of the voltage appears across the resistor, which implies horrible efficiency.
Then the Vf variation is swamped by the larger voltage drop on the resistor, CRUDE but simple.

 

Could I put the driver in front of the power supply and hook up the multiple series (of 15 LEDs [48v]) to the driver to power 756 leds(75%ish of 1000w power supply) ?

 

No.

1) You can make 2 shorter strings of LED's, with 2 resistors, in parallel.
Simple - inefficient.

2) If you must have 15 LED's in series, you need to have a supply voltage greater than (Vf max X 15) PLUS the overhead of the driver.
I would say 60 VDC min.

3) OR you use a LOWER supply voltage and a boost regulator, the supply being LOWER than (Vf min X 15)

4) Or use a fancy buck-boost regulator:
http://www.linear.com/product/LT3956

 

No.

1) You can make 2 shorter strings of LED's, with 2 resistors, in parallel.
Simple - inefficient.

2) If you must have 15 LED's in series, you need to have a supply voltage greater than (Vf max X 15) PLUS the overhead of the driver.
I would say 60 VDC min.

3) OR you use a LOWER supply voltage and a boost regulator, the supply being LOWER than (Vf min X 15)

4) Or use a fancy buck-boost regulator:
http://www.linear.com/product/LT3956

I don't necessarily need 15. Any multiple of 3 or 5. Just need to know the resistors needed. I have a 48v/1000w power supply and just need to make lights with different wattage(achieved by how many series of LEDs I wire in parrallel). I want to be able to just wire the plates to where I can plug multiple ones into the same power supply and they run.

 

I'm curious as to what you think is novel and non-obvious about your system to justify a patent? Connecting series strings of LEDs in parallel is a well-known technique.

 

I'm curious as to what you think is novel and non-obvious about your system to justify a patent? Connecting series strings of LEDs in parallel is a well-known technique.

That's not proprietary. I designed a modulation unit that saves 50% kwh used but produces the same amount of light. Only works with LEDs.