Hi to everyone.
I hope this is the right section of forum to ask this question.
I'm trying to make a led pannel for my aquarium, so i decided to buy some led.
Now, i have 5 led that work at 12 Volt, but two of them have two for each one resistor{8R2 smd resistor 8.2 ohm/1W} that limit the curret flow and the other doesn't have it, so my problem is:
1-how can I size that missing resistor?
2-the 2 led that have a resistor are a 2Watt led and the other are 10Watt
I post a photo of the schematic, i hope everything can be easily underrstand .

 

If the LED's are designed for 12 Volts then they usually have a "built-in" current limiting resistor, someplace.
What is the Model # ?

 

Links to datasheets ?

Regards, Dana

 

If the LED's are designed for 12 Volts then they usually have a "built-in" current limiting resistor, someplace.
What is the Model # ?

Thank you for your reply, anyway, they doen't have a restistor, in fact if i connect direclty to them 12V they start to become extremely hot.

 

Links to datasheets ?

Regards, Dana

Hi and thank you for your reply, i don't have datasheet of them, they are chinese product and the seller didn't give me any datasheet.

 

Hi Tonino, you need to get the specifications for the LED's current rating at a specified voltage. Even the chinese suppliers will state this on the page where you bought them.

 

Thank you for your reply, anyway, they doen't have a restistor, in fact if i connect direclty to them 12V they start to become extremely hot.

Of course they will get HOT.
They are 10 Watt LED's.
They must be mounted to a Heat Sink.
You stated they were rated as "12 Volt LED's", if true then no additional current limiting resistor is needed for 12 volt operation

 

Just as a point of calibration a 1W small component, like a resistor, will burn
your finger.


Regards, Dana.

 

Of course they will get HOT.
They are 10 Watt LED's.
They must be mounted to a Heat Sink.
You stated they were rated as "12 Volt LED's", if true then no additional current limiting resistor is needed for 12 volt operation

I mounted an aluminium heat sink but it looks doesn't work, are u sure that the led don't require a resistor if it work at 12V?

 

Just as a point of calibration a 1W small component, like a resistor, will burn
your finger.


Regards, Dana.

so are you telling me that it's normal to get so hot?

 

I mounted an aluminium heat sink but it looks doesn't work, are u sure that the led don't require a resistor if it work at 12V?

1) What doesn't work?
2) We are still waiting for the Model # of (yellow) LED

 

D.A.T.A.S.H.E.E.T ...

 

so are you telling me that it's normal to get so hot?

Yes, we are telling you that your LED will be hot.
The message stated ... a 1 Watt Resistor will burn your finger.
So now multiply that by 10 TIMES, for your 10 Watt LED.
When you multiply by 10 TIMES, the answer is much bigger = much hotter.
Your (yellow) LED will get hot, very hot - without a heat sink.
Take a photo of your Heat Sink and post it in your reply.

How much current is flowing through the (yellow) LED at 12 Volts ?

 

If you have no datasheet or model#'s, then where did you buy them and do you have a link to the site?? And yes, heat-sinks are required! Do not operate them without proper mounting as you WILL reduce their lifespan.

 

D.A.T.A.S.H.E.E.T ...

Are u kidding me? i just told everyone that i don't have the D.A.T.A.S.H.E.E.T

 

If you have no datasheet or model#'s, then where did you buy them and do you have a link to the site?? And yes, heat-sinks are required! Do not operate them without proper mounting as you WILL reduce their lifespan.

Of course, that is the link:
https://www.banggood.com/it/10W-War...69.html?rmmds=myorder&ID=233&cur_warehouse=CN

 

Hello,

The leds are 9 - 12 Volts and must have a current limited below 1050 mA:



I have set the language on the page to enslish and made a screenshot.

Bertus

 

Yes, we are telling you that your LED will be hot.
The message stated ... a 1 Watt Resistor will burn your finger.
So now multiply that by 10 TIMES, for your 10 Watt LED.
When you multiply by 10 TIMES, the answer is much bigger = much hotter.
Your (yellow) LED will get hot, very hot - without a heat sink.
Take a photo of your Heat Sink and post it in your reply.

How much current is flowing through the (yellow) LED at 12 Volts ?

Ok, the problem is: i don't want a burning led over my aquarium, so the question remain the same....How can i limit the flowing current and reduce the heat?
through the yellow led i don't know how much current is flowing, because i measure with my multimeter but part of the current goes inside the multimeter so i don't know precisely the amount of current, the multimeter tell my 350mA.

 

Hello,

The leds are 9 - 12 Volts and must have a current limited below 1050 mA:

View attachment 172246

I have set the language on the page to enslish and made a screenshot.

Bertus

All right, but that isn't a datasheet, there aren't load curves and current-voltage graph, so i not able to design a circuit that can drive my led properly

 

Hello,

There is enough information for making a circuit.
When you connect the leds in series and drive them with an 1A boost driver like the LM3421, the circuit will be complete.

Bertus