Anyone know about thermal resistance?

[platinumbud]

I have ordered a sheet of aluminium that’s 500mm x300mm x 8mm around a 3rd of a inch thick for 2 Samsung quantum boards, if using a aluminium plate I have heard people say a quarter of a inch is ok, I have seemed the new boards from hlg 550 model it just looks a little thicker than a quarter inch so I have tried to purchase similar quality thickness so I’m guessing this will be enough? I used a thermal resistance calculator and got these results to my measurements 0.00026012601626 c/w ? Totally confused with what this is or means? Or even what would be the rounded up value ect . 

[Davey Jones]

Thermal resistance measured in C/W tells you how many degrees C the temp will raise for every Watt thats dissipated

 

Its similar to Ohms law in electrical circuits the ambient temperature is your ground

 

There will be a resitance between your device and the heat sink and a resistance between the heat sink and ambient

 

The number is really low I would need more details to calculate the final temp that number is probably between the device and heatink

 

A common resisance for transistors (In a DPak package) is 62.5C/W junction to ambient so if you dissipate 2W then the transistor will rise 125C above ambient and a ambient temp of 25C would add to give you a device temp of 150, a hotter ambient would add and make the device above 150C

 

 

[platinumbud]

10 minutes ago, Davey Jones said:

Thermal resistance measured in C/W tells you how many degrees C the temp will raise for every Watt thats dissipated

 

Its similar to Ohms law in electrical circuits the ambient temperature is your ground

 

There will be a resitance between your device and the heat sink and a resistance between the heat sink and ambient

 

The number is really low I would need more details to calculate the final temp that number is probably between the device and heatink

 

A common resisance for transistors (In a DPak package) is 62.5C/W junction to ambient so if you dissipate 2W then the transistor will rise 125C above ambient and a ambient temp of 25C would add to give you a device temp of 150, a hotter ambient would add and make the device above 150C

 

 

Hi thank you for your reply, what other details do you need to know? I know hlg board for 1 quantum board is 0.31 c/w ? 

[Davey Jones]

The datasheet for the heatsink mate

 

0.32C/W is quite low its probably the resistance between device and heatsink we need the other resistance between heatsink and ambient

 

Its just a guess it could be the thermal resistance between device and ambient but it sounds low to me

[platinumbud]

What is the difference between the one I have ordered is it more resistance than the hlg 0.31 ? Led gardener tested all hlg slates and various boards he could not get them to break on heat testing and power going on the boards ect but a lot of this baffles me 

[Davey Jones]

Without seeing the datasheet I have no idea

 

I think the first number you quoted is probably per mK not C but its all guess work

 

Things breaking down with heat takes time I have no idea how long these tests were but decreasing temps seriously extends lifetime we are usually talking years

 

I have explained it as simply as possible, C/W tells us how many C the temp rises for every Watt thats dissipated, do you understand this? What baffles you?

 

Cant calculate anything without a datasheet and details of the devices, its just how it is details are important

[platinumbud]

Hi yes I understand c w stands for Celsius and watt, the data sheets are on www.horticulturallightinggroup.com  under v2 boards it says a aluminium plate or heatsink might be required if running each board more than 75 Watts, the hlg driver is 240h c2100a . I don’t know how to add a proper link to the website but it is above and the data sheet is available for the v2 boards and the drivers are used on all the 260 watt kits, hopefully you might be able to help out thanks.

Edited June 9, 2018 by platinumbud