selecting heatsink

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The power dissipated by the resistor depends on the resistance and voltage across it.

Use ohms law.
**broken link removed**
 
i mean in the datasheet, it says the power rating is 10watts, what does that actually mean?

and do i really need a heatsink for that kind of resistor. if yes, could you please tell me which type should i use?

Thanks in advance
 
The power rating is the maximum power it can dissipate without being damaged.

The size of heatsink you require is determined by the amount of power the resistor will need disipate in the circuit.

To find out how much power your 75hm: resistor will dissipate with 24V across it, use ohms law; see above.
 
forever99482 said:
i mean in the datasheet, it says the power rating is 10watts, what does that actually mean?

and do i really need a heatsink for that kind of resistor. if yes, could you please tell me which type should i use?

Thanks in advance
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With 24 volts across 75 ohms, you will be dissipating 7.7 watts. If I am interpreting the datasheet correctly, the maximum power this package will handle without a heat sink is 5.5 watts. The recommended heat sink is 415 sq cm, at least 1mm thick. I think you get to count the entire surface area, so if you use one with fins, it would be pretty small. If you use a flat plate, I think it can be about 200 sq cm on each side, equivalent to a plate which is 10cm X 20cm, or 14cm X 14 cm, or... I think you get the idea.
 
Dough, I wanted him to figure it out for himself so he would learn from the experiance and you've gone and ruined it now Ron!
 
Hey Hero, I like that ohms law graphic, I think I'm going to print it and make some coasters with it, would make a nice conversation piece. The nice solid colours will make it easy to pretty in GIMP too.
It's slightly amusing that the letters on each quadrant starting from the upper left going clockwise spell 'wire'
 
Hero999 said:
Dough, I wanted him to figure it out for himself so he would learn from the experiance and you've gone and ruined it now Ron!
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You're such an optimist.
I guess I should have fed some hints instead of the answer. Hopefully, he'll go to the datasheet and try to figure out where I came up with those numbers. Are you listening, forever99482?
 
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Sceadwian said:
Hey Hero, I like that ohms law graphic
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I have Google image search to thank for that.

I think I'm going to print it and make some coasters with it, would make a nice conversation piece.
Click to expand...
Good idea, I think I'll do the same myself.

The nice solid colours will make it easy to pretty in GIMP too.
Click to expand...
I've always prefered vector graphics for this sort of thing, I might make my own in OpenOffice.org Draw.

It's slightly amusing that the letters on each quadrant starting from the upper left going clockwise spell 'wire'
Click to expand...
I didn't notice that!
 
thanks everyone

but then i found out that the wirewound resistor is not hot at all after i plug in the 24V @_@, so I'm just sticking to it without a heatsink.
 
forever99482 said:
thanks everyone

but then i found out that the wirewound resistor is not hot at all after i plug in the 24V @_@, so I'm just sticking to it without a heatsink.
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Have you measured the voltage and the resistance and/or the current? 7.7 watts in that package will get hot.
 
haha, wire

Where do you get all your pretty pictures hero
 
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