Author Topic: Dc current smoothing?  (Read 2090 times)

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Offline SounduserTopic starter

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Dc current smoothing?
« on: February 07, 2016, 02:45:26 pm »
My dc pumps turn on and off to create random flow and waves.
This causes the power supply fan to go on and off with the pumps. Due to current being drawn 50% of the time.

How can I calculate the value of a capacitor to even out the current draw?

The pumps draw around 1 amp at 24 volts.
I'd like to add a cap or two to each pump to smooth the draw to a constant 500ma.
With minimal ripple.

Thanks for you help.

Google just gives calculators for Ac supplys.
 

Offline Chalcogenide

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Re: Dc current smoothing?
« Reply #1 on: February 07, 2016, 02:52:56 pm »
Capacitors can only smooth out relatively fast transients; you would be better off removing the original fan and installing a quieter one, maybe always running at a lower rpm (1/2 or so). Or, use a bigger power supply that can run fanless at a 1A load.
 

Offline SounduserTopic starter

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Re: Dc current smoothing?
« Reply #2 on: February 07, 2016, 04:42:34 pm »
Is once or twice a second too slow?
 

Offline Chalcogenide

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Re: Dc current smoothing?
« Reply #3 on: February 07, 2016, 05:39:39 pm »
To have an effective smoothing at <1Hz you would an irrealistic LC filter at 0.1Hz or so. With a 1 Farad capacitor and a 1 Henry inductor, assuming a 24 Ohm load (1A at 24V) you would get roughly 0.16Hz cutoff frequency, and it still still wouldn't completely smooth out the current draw (and both values of the filtering elements are absolutely huge and unrealistic, not to mention incredibly expensive if you could even find them).
 

Offline Marco

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Re: Dc current smoothing?
« Reply #4 on: February 07, 2016, 07:14:58 pm »
A 24V/2A power brick is ~10$ delivered ...
 

Offline SounduserTopic starter

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Re: Dc current smoothing?
« Reply #5 on: February 07, 2016, 08:17:01 pm »
I've replaced 5 wall warts with a 24 volt psu.
No worries if it's impractical. It's not a big problem. I was hoping a 10000 mike cap would even out the draw.

No problems.
 


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