Need Help for my DIY Led light

[matashi]

First of all, I have no background in electronics or whatsoever. Just been doing trial and error and loads of google + youtube. I have now DIY a 108w light but have problem powering up the correct way. my power supply burns my led within 10mins. The last round of testing cost me about half of the Leds burnt out. Now i have replaced them and all tested to be working. Just need advice to prevent burning out again.

Attachment 45995

Is there anything that i'm missing?

I've gone too far to give up on this project now

Please help me.......

[Shadow]

You choose wrong power supply. You cannot use normal power supply, you need current limited power supply or also known as led driver. Alternatively you can use resistor to limit the current but then will not be power efficient.

You are currently connecting 700mA rated led to 10A power supply, of course it burn. Led is unlike normal light bulb, its a diode, short circuit in forward bias by nature so basically you running about 10A through it

Get led driver which is rated the same as your led, for this case 700mA.

[matashi]

Wa very confusing. I read somewhere that to power 108w of LED I need 10A x 12V = 120w. Need minus 10% off for buffer.

Boss please help guide me which specification adaptor I should be using


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[matashi]

Can I buy any led driver 700mA? What voltage and wattage to look out for?

Since I already have 10A adaptor, what's the alternative resistor I can use?

Sorry ah too many questions total noob here but DIY freak


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[Shadow]

You search aliexpress or dealextreme or eBay for 700mA led driver. It should pop up with various voltage model. You will need to connect all your led in series, choose the one that match. For example if you are using 10 leds 3V each, then choose 30V 700mA led driver. You can get something lower like 680mA but you cannot use say 800mA driver

[matashi]

Wow thanks! I think I know what to look for now.

Credits to you when the thing is up!


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[Shadow]

On your current design, you need 2.7 ohm resistor in series with 3x3.4V leds. You should not mixed the 2.4V and 3.4V led. You also need 1.5watt rated resistor.

[matashi]

Just to be sure, I need at least a 36v 700ma driver. Right?


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[matashi]

If I change the red LEDs to white ones. Do I still need resisters with led 700ma driver?


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[Shadow]

You do not need resitor with led driver.

[matashi]

I better not use the 10A anymore. Resistors only make my headache worse


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[Shadow]

You have 36 LEDs, so you will need more than one driver. My guess will be 3 driver, 10 to 12 led in series for each driver.

[matashi]

I can't find any cheap drivers with high voltage. Gotta rethink the wiring again. Maybe use 4 drivers connecting 9 LEDs each.


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[seudzar]

Try look for meanwell led driver, they are one of the cheaper and reliable led driver. Their distributor is smsystem.com.sg. You can try if they are willing to sell to you.

[gregnng]

Use led fluroscent tube with built in led driver, easier to assemble with light fixtures. On off switch on live wire to one end of tube, other end of tube to neutral wire. Runs off 230v ac.

[matashi]

Today went down sim lim tower to look for the LED drivers. I used resistors for all groups of 12 instead. Cheap cheap at $6 only. Or else buy drivers will cost too much to this project.

With 4 x 12cm fans, I manage to lower temp by 2 degrees. Pearling is observed within 30mins of light on.

Thanks to all help here given by fellow forumers


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[Suzerolt]

Nice DIY. Any pics of the actual lights?


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[limsteel]

5 x 10w White LED on each side of my 5ft tank Yellow tint due to Black water extract.

Cooled by 2 x 3.5inch fan (on each side), not in pic as I am troubleshooting connection issue. Power by Computer PSU 12V

Plan enhancement:
- Increase the resistor or install higher power fan or Attach heat sink to the mounting plate, 2 of my LEDs already dead.
- use light reflector instead of my aluminum plates, too much (wasted) light reflected off the water surface.

[Shadow]

That is why should get led driver. Current limiting resistor work when none of the led spoil but if one of them spoil, the rest will follow soon unless you re-calculate the resistor value.

For example
10x3W led, each led rated 3V and 1A. Power supply used 40V 5A. All led are in series, that mean voltage across 10 led would be 30V. Voltage across the resistor would be 40-30=10V. To get 1A you need 10 ohm resistor.

Now let say 2 of the led spoil, voltage across 8 led would be 24V. Voltage across resistor 40-24=16, thus the current running through would be 16:10=1.6A and the led only rated for 1A. So more led will spoil.

[limsteel]

Cannot agree with you fully. If you connect all your LED:
-In series, if one blow all the rest of the working LED will also be turned off. Since it is no longer a close circuit. No over loading.
- In parallel, any LED blow, the standard 12V still applies and the resistor will still limit the current to the individual connection.

I happen to connect 1 Resistor in series to 5 x 3 LED connected in parallel. This mistakes is as what you mentioned. 1 LED blow, the rest of the LED will get much more current and hasten the rest of the LED to blow up faster.