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# MCP350 Loud and noisy? - Page 3

Pump won't even start up with a 100ohm resistor on it...
Quote:
Originally Posted by iCrap

Pump won't even start up with a 100ohm resistor on it...

What the heck? Adding a resistor won't filter jack, it will drop the voltage making the pump run slower. That's one way to lower the noise footprint but you're better off using a fan controller that can support 20w loads so you don't lose out on the max performance. PSU's already have ripple suppression. Go read stuff at jonnyguru.com and you'll see what I mean.

Quote:
For this you need a few equations with the following parts.
I = current (Amps)
U = voltage (Volts)
R = Resistance (Ohms)
W = Power draw (Watts)

U = I * R, That is voltage dropped across a electrical part is the current times the resistance.

We know voltage and current and can calculate the "static" electrical resistance of the pump.

12 = 1.5 * R -> 12/1.5 = 8 Ohm.

Resistors in series have to share a voltage drop, thus adding a resistor in series with the pump reduces to voltage for the pump. The equation for this is below along with the calculation for the drop across the pump when using a 4.4 Ohm resistor.

(Rpump/(Rpump + Rseries)) * U = voltage drop across the pump. (8/(8+4.4))*12 = 7.75 Volt.

7.75 Volt is a bit less than what you wanted, but maybe he thought you wanted 10 Watts.
One equation for calculating power draw is:

W = U * I

The trick is that the current (I) depends on the resistance of both the pump and the series resistor.

I = U / (Rpump + Rseries) -> I = 12 / (8 + 4.4) = 0.97 Amps

Going bach to the power consumption again.

W = U * I -> W = 7.75 * 0.97 = 7.5 Watts.

Looks a little low to me, but I am tired and calculated with the resistance expected from your 18 watts number and it has been a while since i calculated these kind of thing with motors.

The horrible realisation you should have from these equations is when you use them on the resistor, as it is taking on a voltage drop of 4.25 volt at 0.97 Amps, that is more than 4 Watts. Usually a resistor can handle around 0.2 Watts without burning to a crisp.

Maybe I should just have started by writing, you should not use a resistor to drop voltage across that pump, it has way to high a power draw.

See if you can find a voltage controller capable of handling 1.5 Amp, as you will need something with a solid heatsink or PWM based techniques.

source
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 The 3930 (23 items) Junior's 3820 (18 items) SO's HTPC 2500K (17 items)
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i7 3930K Asus Rampage IV Extreme XFX 7970 Black Edition Diamond 7970 x3
RAMHard DriveHard DriveOptical Drive
Samsung 2400mhz 4gb x4 Samsung 830 128gb x2 Seagate 3TB 7200rpm Asus BD ext
CoolingCoolingCoolingCooling
Alphacool Monsta 480 + Nova 1080x2 Alphacool XP3 + EK RIVE Quad EK-FC7970 GT AP15 x22
CoolingOSMonitorPower
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CaseAudioAudioAudio
Corsair 700D Yamaha NeoHD YMC-500 Dayton Audio BS36 Energy MSW M6
Quote:
Originally Posted by tsm106

What the heck? Adding a resistor won't filter jack, it will drop the voltage making the pump run slower. That's one way to lower the noise footprint but you're better off using a fan controller that can support 20w loads so you don't lose out on the max performance. PSU's already have ripple suppression. Go read stuff at jonnyguru.com and you'll see what I mean.
source

I did try plugging into my sunbeam rheostat, lowering it did help a bit but obviously it also killed the flow speed.
Quote:
Originally Posted by iCrap

I did try plugging into my sunbeam rheostat, lowering it did help a bit but obviously it also killed the flow speed.

There in lies the rub. Get a quieter pump. Get a real MCP350 or better yet 35x.
 The 3930 (23 items) Junior's 3820 (18 items) SO's HTPC 2500K (17 items)
CPUMotherboardGraphicsGraphics
i7 3930K Asus Rampage IV Extreme XFX 7970 Black Edition Diamond 7970 x3
RAMHard DriveHard DriveOptical Drive
Samsung 2400mhz 4gb x4 Samsung 830 128gb x2 Seagate 3TB 7200rpm Asus BD ext
CoolingCoolingCoolingCooling
Alphacool Monsta 480 + Nova 1080x2 Alphacool XP3 + EK RIVE Quad EK-FC7970 GT AP15 x22
CoolingOSMonitorPower
MCP35x x3 Win7 Pro x64 Asus VS229H-P x3 Lepa 1600
CaseAudioAudioAudio
Corsair 700D Yamaha NeoHD YMC-500 Dayton Audio BS36 Energy MSW M6
 The 3930 (23 items) Junior's 3820 (18 items) SO's HTPC 2500K (17 items)
CPUMotherboardGraphicsGraphics
i7 3930K Asus Rampage IV Extreme XFX 7970 Black Edition Diamond 7970 x3
RAMHard DriveHard DriveOptical Drive
Samsung 2400mhz 4gb x4 Samsung 830 128gb x2 Seagate 3TB 7200rpm Asus BD ext
CoolingCoolingCoolingCooling
Alphacool Monsta 480 + Nova 1080x2 Alphacool XP3 + EK RIVE Quad EK-FC7970 GT AP15 x22
CoolingOSMonitorPower
MCP35x x3 Win7 Pro x64 Asus VS229H-P x3 Lepa 1600
CaseAudioAudioAudio
Corsair 700D Yamaha NeoHD YMC-500 Dayton Audio BS36 Energy MSW M6
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