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Parallel resistors...
- Thread starter knockbill
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petehall347
the brandy coffee man
yes theory says it will do .
whoaru99
Epic Member
It will be 1 watt total, but if the resistors are not truly equal resistance the power dissipation will not be spilt equally. One of them would be over the rated 1/2W dissipation if so.
For example, if one was 8300 ohms and the other 8100 ohms, the former would dissipate 494mW and the latter 506mW.
Of course, if the total actual dissipation is well under 1W, even if different resistances, either one could still be within its individual 1/2W rating.
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FlaCharlie
Super Member
How much wattage does the resistor need to dissipate in your application? Dissipating close to the rating of a resistor is asking for trouble / early failure. Dale and others make some nice small wirewounds with 3 to 5 watt ratings.
If you have 10K and 20K, two 10K and one 20K in parallel, gives exactly 4K.
Two 10K and a 22K gives 4.07K. That's less than 2% off. If you have a bunch of resistors, you can probably "tolerance cherry pick" (pick some that are slightly lower resistance than spec for the values needed) and get even closer.
Regards,
Gordon.
Two 10K and a 22K gives 4.07K. That's less than 2% off. If you have a bunch of resistors, you can probably "tolerance cherry pick" (pick some that are slightly lower resistance than spec for the values needed) and get even closer.
Regards,
Gordon.
knockbill
Lunatic Member
I got it,,, I used 10W in the mules, but they are way too big for the chassis,,, I just need 1W, and picked 2 matched 1/2W that bring the total to 4.04k/1W,,, got the amp fired up in its chassis, and set bias,,, That was the plan,,, got some 1 and 2W on the next Mouser order...
I'm aware that R has to match to draw equal current,,, problem is you can't measure them separately while they're powered, they may drift differently when hot, so they aren't in permanently... This was a temp solution,,, thanks for confirming Wattage...
I'm aware that R has to match to draw equal current,,, problem is you can't measure them separately while they're powered, they may drift differently when hot, so they aren't in permanently... This was a temp solution,,, thanks for confirming Wattage...
FlaCharlie
Super Member
Have you seen my earlier post: http://www.audiokarma.org/forums/index.php?threads/free-shipping-on-parts-orders.739513/
You can save some money, especially if you only need a few parts.
You can save some money, especially if you only need a few parts.
How much voltage is across the resistor? You can use Ohm's Law for power (P=V^2 / R) to determine the total dissipation. If the total dissipation is less or equal to 1/2 the combined dissipation of the resistors, combined (since they're ostensibly identical values), you don't have anything to worry about. Even if there's drift, it won't be enough to overload either resistor.
Regards,
Gordon.
