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heat from a resistor
- Thread starter orion456
- Start date
- Joined
- Apr 19, 2003
The wattage rating of a resistor shows its maximum carrying capacity;
i=e/r, and p=i*e, therefore the wattage the resistor will actually carry during use is variable depending upon the ohms of the resistor and the voltage of the circuit.
Once you've calculated the actual wattage load on the resistor, you can calculate the thermal output. This, however, will vary depending upon the resistor's internal design. This publication has some good information about resistor design and thermal characteristics.
i=e/r, and p=i*e, therefore the wattage the resistor will actually carry during use is variable depending upon the ohms of the resistor and the voltage of the circuit.
Once you've calculated the actual wattage load on the resistor, you can calculate the thermal output. This, however, will vary depending upon the resistor's internal design. This publication has some good information about resistor design and thermal characteristics.
- Joined
- Nov 28, 2003
- Location
- Appleton, Wisconsin
How many volts will be across it, and how many amps through it? Multiply those two values, it gives you the wattage you will have on the resistor. If its under 1, you will be fine and not need to worry about it burning out. But if you're just wondering about how much heat it will add to ambient temps in your computer, probably nothing noticeable.
- Joined
- Jun 5, 2003
- Location
- TEH INTERNETS
If said resistor is part of a volt mod it should most certainly NOT get hot. If it does, that's A Bad Thing™
- Joined
- Apr 19, 2003
orion456 said:
Yes. But why are you using a resistor for this? Why not just do a volt mod?
R= U/I so this fan has an internal resistance (yes I am simplifying) of 12/0.17 ~= 70 Ohms.
the full resistance of the contraption is therefore 70+43=123 ohms. Again I = U/R means
12V / 123 = 0,1 ampere.
If the resistor has less than 10V between its pins (which it will), all will be alright
the full resistance of the contraption is therefore 70+43=123 ohms. Again I = U/R means
12V / 123 = 0,1 ampere.
If the resistor has less than 10V between its pins (which it will), all will be alright
OP
- Joined
- May 31, 2004
- Thread Starter
- #8
hafa said:
I want the fan to run at 7 volts so I figured the easiest way to do that is to create a voltage divider using a resistor. Works great, but I just wanted to be sure it was safe.
UPDATE: I stuck a temp probe next to the resistor and after running for about 20 minutes it's reading 40c. It seems like the maximum temps quoted for resistors is around 70c, so my temp looks great. Yes?
Last edited:
OP
- Joined
- May 31, 2004
- Thread Starter
- #10
Whoa there you go. I thought it was a nice idea and now Zalman offers a "special" adapter that makes the fan quiet....ummm, adds a resistor! And after all that soldering I had to do! Kewl.
In fact I like the idea of an adapter so things can be adjusted...I'm going to make a few.
In fact I like the idea of an adapter so things can be adjusted...I'm going to make a few.
