LED Heat Management

MidnightSun72

MidnightSun72

Well-Known Member
Ok so I am trying to find a method to calculate how much heat an LED strip makes and how much heat sinking is needed.

so from using google I found this link:
www.ledsmagazine.com

Fact or Fiction – LEDs don’t produce heat

An often-quoted advantage of LEDs is that they don’t produce heat, and are cool to the touch. Fact or fiction?
www.ledsmagazine.com www.ledsmagazine.com

In the section under "Calculating Thermal Resistance"
An equation is listed:

temperature change = thermal resistance x LED power (where LED power = voltage x current)

Taking the Seoul semiconductor strip
SMJD-3622120B-XXN1A as an example.
Data sheet below
This strip has a Thermal Resistance of 0.3 *C/W (value given in data sheet)
The nominal current is 0.65a and Forward voltage is 33.6V.
So the temperature change of the LED strip should be

Delta T= 0.3 *C/W X (0.65X33.6)W = 6.55*C

for the EB Gen 2 strips BXEB-L0560Z-35E2000-C-B3
Using the temperatures provided in this link we can work back and figure out the thermal resistance of the strip.


Thermal resistance = rise in temperature form ambient/strip wattage (Amps X Volts)

thermal resistance = (45*C (Temp of back of strip)- 26.7 (ambient t)) / (19.5 X 0.625) = 1.5*C/W <---this could be lower in reality since the guy did record back of strip temps as low as 37*C so if you work it out with that you get a resistance of 0.845*C

Is it possible the Seoul strip is that much better at heat management? Am I even understanding the equations correctly?
 
Last edited:
electronics.stackexchange.com

How much heat do power LEDs dissipate?

I am using this 10 W RGB LED, unfortunately DX does not provide a datasheet for it. I don't know how efficient these power LEDs are... so approximately how much applied power is converted into ligh...
electronics.stackexchange.com electronics.stackexchange.com
This post may help, if not the site may be able to.
If neither.. fuck it I tried lol I'm no electrician. I'm just available.
 
MidnightSun72 said:
Ok so I am trying to find a method to calculate how much heat an LED strip makes and how much heat sinking is needed.

so from using google I found this link:
www.ledsmagazine.com

Fact or Fiction – LEDs don’t produce heat

An often-quoted advantage of LEDs is that they don’t produce heat, and are cool to the touch. Fact or fiction?
www.ledsmagazine.com www.ledsmagazine.com

In the section under "Calculating Thermal Resistance"
An equation is listed:

temperature change = thermal resistance x LED power (where LED power = voltage x current)

Taking the Seoul semiconductor strip
SMJD-3622120B-XXN1A as an example.
Data sheet below
This strip has a Thermal Resistance of 0.3 *C/W (value given in data sheet)
The nominal current is 0.65a and Forward voltage is 33.6V.
So the temperature change of the LED strip should be

Delta T= 0.3 *C/W X (0.65X33.6)W = 6.55*C

for the EB Gen 2 strips BXEB-L0560Z-35E2000-C-B3
Using the temperatures provided in this link we can work back and figure out the thermal resistance of the strip.


Thermal resistance = rise in temperature form ambient/strip wattage (Amps X Volts)

thermal resistance = (45*C (Temp of back of strip)- 26.7 (ambient t)) / (19.5 X 0.625) = 1.5*C/W <---this could be lower in reality since the guy did record back of strip temps as low as 37*C so if you work it out with that you get a resistance of 0.845*C

Is it possible the Seoul strip is that much better at heat management? Am I even understanding the equations correctly?
Click to expand...


Just reading through this Bridgelux Document

page 12of 31 references that the Vero datatsheet " Rj-c value was found in the Vero Module Datasheet to be 0.28 °C/W "


So pretty similar to the Seoul Semiconductor. I can't wrap my head around how the Bridgelux strips run the temperatures they do at 0.7a and 39v for the 4ft or 0.7a and 19.5 for the 2 ft. Every time I run it through a calculator I get very high source temperatures that don't make sense. Any mechanical engineers in the house?

I feel like half of whats tripping me up is the relation between the thermal resistance of Rth (case to base) the resistance of the whole system to ambient.
 
1212ham said:
1 watt = 3.412142 BTU.
Click to expand...
Yes that is factual.

What I really need to understand is how many BTU per hour a strip can shed at an ambient temperature of 35* Celsius. And I want it in equation form so I can work it out for any PCB.

This way I can look at any strip and figure out it it needs a heat sink and how much big. I dislike doing things just because that's , though it's great to have that as a fall back.

I'll just keep reading. Don't worry I'll update this when I make a breakthrough.
 
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MidnightSun72 said:
Ok so I am trying to find a method to calculate how much heat an LED strip makes and how much heat sinking is needed.

so from using google I found this link:
www.ledsmagazine.com

Fact or Fiction – LEDs don’t produce heat

An often-quoted advantage of LEDs is that they don’t produce heat, and are cool to the touch. Fact or fiction?
www.ledsmagazine.com www.ledsmagazine.com

In the section under "Calculating Thermal Resistance"
An equation is listed:

temperature change = thermal resistance x LED power (where LED power = voltage x current)

Taking the Seoul semiconductor strip
SMJD-3622120B-XXN1A as an example.
Data sheet below
This strip has a Thermal Resistance of 0.3 *C/W (value given in data sheet)
The nominal current is 0.65a and Forward voltage is 33.6V.
So the temperature change of the LED strip should be

Delta T= 0.3 *C/W X (0.65X33.6)W = 6.55*C

for the EB Gen 2 strips BXEB-L0560Z-35E2000-C-B3
Using the temperatures provided in this link we can work back and figure out the thermal resistance of the strip.


Thermal resistance = rise in temperature form ambient/strip wattage (Amps X Volts)

thermal resistance = (45*C (Temp of back of strip)- 26.7 (ambient t)) / (19.5 X 0.625) = 1.5*C/W <---this could be lower in reality since the guy did record back of strip temps as low as 37*C so if you work it out with that you get a resistance of 0.845*C

Is it possible the Seoul strip is that much better at heat management? Am I even understanding the equations correctly?
Click to expand...
Don't overthink it. If you run lots of strips at low current then you don't need sinks you can just use aluminium L shaped plates. Add a fan and you'll be good
 
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