Powering 1000 LEDs in a grid

[JanaJ]

Hello, I am making a light installation of 1000 leds in a grid 20x50 leds. I want to connect 20 leds in a series and then connect each series in parallel (50 lines in total). Each led is about 3.1V 20mA. Can anyone help me with what adapter I would use to power this? (I have a regular EU plug 230V 16A). And do I need to put resistors? And where? Final question, because of the design restrictions I can fit max of 24awg cables in the series part of the installation, but I can put any size of a cable between the lines - for the parallel connection. What size of a cable would I use? I hope someone finds this possible and challenging enough to help me out.

 

[ronsimpson]

What is the part number for the LED?
3.1 volt X 20 = 62 volts (more or less)
20mA x 50 = 1000mA = 1A

Why not use 1A 3.1 volt LEDs? or 300mA? Why not bigger LEDs?

 

[Externet]

The text "400mA per line" is wrong. It is 20mA.
Rightmost LEDS must be connected together in the column to power return.
"?" should be about 62 V capable of at least 1A as told above, not 230/16A

 

[ronsimpson]

not 230/16A

It might be that his connection to the power grid is 230V/16A.

 

[Externet]

Correct. Seems he is not discerning 230V mains being AC and LEDs need DC. The bottommost symbol could be a DC voltage source missing connection to missing rightmost column connection. Perhaps the '?' is for the OP, a questioned resistor.
The "6AWG cable" is way out of whack. 24AWG everywhere is fine.

 

[Pommie]

Wiring 66 in series with a 1.2k 1w resistor via a full bridge rectifier would give you 20mA RMS. You'd need 15 lines to give you 990 LEDs. If you need 1000 then make 10 rows with 67.

MIKE.

 

[JanaJ]

Wiring 66 in series with a 1.2k 1w resistor via a full bridge rectifier would give you 20mA RMS. You'd need 15 lines to give you 990 LEDs. If you need 1000 then make 10 rows with 67.

MIKE.

Interesting solution. Do you know if 24awg cable work at length 66m? (each led is 1m away of the other. They are in 1m tubes sticking out, and max 24 awg cable fits in the tube). I am worried about voltage drop.

 

[JanaJ]

It might be that his connection to the power grid is 230V/16A.

yes yes. the power in the plug is 230V 16A.

 

[Pommie]

The resistance of 66m of 24awg is about 5.5Ω so nothing to worry about. Total voltage drop 5.5x0.02 = 0.11V.

Mike.

 

[Externet]

Another way:

A-------------|<|---------|<|-------|<|-------- . . . . . -----|<|----------B series of 210 LEDs
A-------------|>|---------|>|-------|>|-------- . . . . . -----|>|----------B Series of 210 LEDs

Repeat for 840 LEDs

230VAC mains applied directly to A and B, no rectification, no transformer; but provides no isolation from mains either. Done it several times with less number of LEDs.
By the way, a brigde rectifier to provide the LEDs with DC can be made of LEDs, instead of diodes.

 

[Pommie]

How will 210 LEDs with Vf of 3.1V be lit by 230V? And the bridge need to handle 15x20mA so rectifiers are probably a good idea.

Mike.

 

[Externet]

Mental fart... Wrongly considered peak to peak instead of only peak, as only one string is on at a time. So about half the LEDs count, like 105.

 

[Pommie]

That is why i stated RMS above. The current will briefly exceed the 20mA when peak occurs but the RMS current will be 20mA. Due to this, it's very important that no smoothing capacitors are used. Someone on this forum may have something to say about the 100Hz flicker.

Mike.

 

[ChrisP58]

Is the entire 50 x 66 meter strings of LEDs adequately protected from being touched?

If not, then having it powered directly from the AC Mains is a Very Bad Idea.

 

[Pommie]

Is the entire 50 x 66 meter strings of LEDs adequately protected from being touched?

If not, then having it powered directly from the AC Mains is a Very Bad Idea.

Agree completely. Personally i wouldn't have more than 48V and have 70 strings with 14 LEDs per string. That would only require 1.4A and would be much safer. A suitable power supply can be had on ebay for around $20.

Edit, as you need a grid of 50x20 I'd do 100 strings with 10 LEDs in each powered from 36V. This would require 2A - quick look on ebay finds this which should be safe.

Mike.

 

[JanaJ]

Agree completely. Personally i wouldn't have more than 48V and have 70 strings with 14 LEDs per string. That would only require 1.4A and would be much safer. A suitable power supply can be had on ebay for around $20.

Edit, as you need a grid of 50x20 I'd do 100 strings with 10 LEDs in each powered from 36V. This would require 2A - quick look on ebay finds this which should be safe.

Mike.

I am glad you are saying that. After some consideration, even though it's completely out of the reach of people, I decided to stay under 48V. I'll do 15leds in line with a 390R 1W resistor. Then connect the lines in parallel to 48V/1.5A power source. I hope my calcs are correct. Thank you all for your help!

 

[Pommie]

If you do 15 LEDs per line then 15*3.1 is 46.5. This only gives you 1.5V to regulate current (BTW, 1.5/0.02=75Ω).

That is why I suggested 10 and 36V as this gives you 5V overhead and a resistor of 250Ω.

Note that the power is V * I so 5*0.02 = 0.1W - so 1/4W resistors will be fine.

Mike.

 

[JanaJ]

Like this? Am I wiring the positives and negatives ok?

 

[Pommie]

Yes, that's correct. However, in the link to the power supply above a 2A supply is $20 and a 5A is $24 - for the extra $4 and increased flexibility I'd get a higher current supply.

Mike.

 

[ChrisP58]

JanaJ, have you posted the datasheet for the LED you plan to use? I recommend doing so.

The reason is that the forward voltage of LED's can vary and are dependent on operating conditions. Reading what, and how, it is spec'd on the datasheed can give us a better understanding of it.

With 15 LEDs in series, a little bit of error can add up. You may need a different resistor.