Powering 1000 LEDs in a grid

[Pommie]

Good call ChrisP58.

Mike.

 

[JanaJ]

thanks. here is the datasheet for the leds. unfortunatelly, i dont know much of what i am looking at. i just measured the values i am using myself. i'll be very glad if someone can look it. thank you!!

 

[Pommie]

That states 3.1V at 20mA with a max current of 25mA so should be fine. You'd need a lot of diodes with Vf at the low end to cause any problems. If you were unlucky enough to get 10 diodes all with the min Vf of 2.8V then the current would be 32mA. This is extremely unlikely but if it worries you change the resistor to 320Ω.

Mike.

 

[ronsimpson]

here is the datasheet

Thanks, I asked for that in pot #2. Or at least the part number.
The forward voltage is as low as 2.8V, typically 3.10, and as high as 3.8 volts. Combine that with the idea that the power line varies some. This makes picking the right resistor hard.

Think about 3.8V diodes and a low line voltage. or 2.8V diodes and a high line voltage.
Also, at 20mA you need to keep the air temperature around the LED below 40C. (not room temperature but air temp. If you enclose the LEDs the temperature will climb.)

 

[Pommie]

Ron, I'm confused by your concerns. If the OP ends up with a string of 10 LEDs at 2.8V then the resistor needs to drop 8V. This is easily achieved by a 320R resistor. I'm also fairly sure the 36V from the power supply won't vary with line voltage. Or, did I miss something?

 

[ronsimpson]

36V from the power supply won't vary with line voltage.

Sorry, there has been many comments about line voltage and AC. I did not see where we switched to an isolated supply.

There are many "constant current" LED power supplies. They work best on a single string of high current LEDs.

 

[Pommie]

The whole thread has jumped all over the place. Hopefully, the OP can now construct a safe version of the grid.

Mike.

 

[ronsimpson]

construct a safe version of the grid

Where is your sense of adventure?

In my lab, I have one source of power for the lights. A different source for the plugs. And I try to have a third power for the project to live on.
There are too many labs where one breaker controls all power.
Experience: Blinding flash of light, clap of thunder and all the lights go out. There I sit in the dark. My ears are ringing. Eye can not focus on anything. "Is this Heaven or Hell?"

 

[Pommie]

Where is your sense of adventure?

If you saw my bench you wouldn't ask that question.

Mike.

 

[JanaJ]

I chose this power source: MEAN WELL CLG-150-36
151,2W; 36VDC; 31÷41VDC; 4,2A; 90÷264VAC; IP67

I picked the one with a higher current as recommended by Mike.

The installation is near water, so I am waterproofing the branched connections. I have a soldered "T". Do you recommend one type of isolation treatment over another? I thought to use liquid electrical tape. The installation will be there only for four days, so I am not worried about it wearing off eventually. I am worried about fast application and a complete seal. Thank you.

 

[JanaJ]

here is a datasheet for the power source

 

[Pommie]

That is a constant current supply - you need a constant voltage supply.

Mike.

 

[JanaJ]

Oh right, that's what you were saying just above. Second try:

MEAN WELL ELG-150-36DA
150W; 36VDC; 4,17A; IP67; communication DALI

Can I ignore the DALI line?

 

[Pommie]

That's also constant current. They are designed to drive much higher power LEDs and aren't suitable if you are paralleling strings together.

It's possible that will work but I've not used those kind of supplies. Maybe someone else can advise.

Personally, I'd use a plug in adapter as you'll have to insulate the cable supplying it anyway.

Mike.

 

[JanaJ]

thank you.