Author Topic: Why pumps of coffee makers have that horrible noise  (Read 589 times)
dor123
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Why pumps of coffee makers have that horrible noise « on: November 10, 2024, 12:10:31 PM » Author: dor123
https://www.youtube.com/watch?v=i3PDMXeQjMk
In that video, I operated the tutors coffee maker to show you how a horrible 50hz "BRRRRRRRRRRRRRRRR" noise its pump makes.
This is happening with household and commercial coffee makers.
Why this is happening?
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Re: Why pumps of coffee makers have that horrible noise « Reply #1 on: November 10, 2024, 02:07:24 PM » Author: RRK
Because these are using 50Hz electromagnet (running on a half-wave rectified mains through a single diode) to drive a pump's piston. Water pressure involved is rather high (>10bar) so are mechanical forces, making this thing noisy.
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Medved
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Re: Why pumps of coffee makers have that horrible noise « Reply #2 on: November 11, 2024, 06:17:11 AM » Author: Medved
They use resonance tuned vibrating plunger piston system. The piston assembly (the piston itself, with the attached magnet) mass is tuned with spring holding it in place to the mains frequency, so although the spring itself is rather stiff, at the 50Hz it vibrates rather freely.
There are two main reasons: They are very simple (the only moving part is the piston assembly and the ball check valves; no crank or so) and inherently impose limitation on the water pressure they can generate, so the systemdoes not explode even when it get clogged.
The drawback is the pumps are shaking while in operation, mainly when there is no back pressure.

The arrangement may usea single diode so just one polarity is pulling it in, or what I have seen was the use of a permanent magnet in the plunger, so one polaritu pulls it into the coil and the other pushes out. Either way, the generated vibration is at the feed frequency, so the 50Hz.
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Re: Why pumps of coffee makers have that horrible noise « Reply #3 on: November 11, 2024, 06:32:38 AM » Author: dor123
It is possible to use other types of pumps like rotary vane pump or scroll pump?
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Re: Why pumps of coffee makers have that horrible noise « Reply #4 on: November 11, 2024, 10:16:14 AM » Author: RRK
Sure, but the market is price-sensitive, so the lowest cost pump type is chosen. Despite simple construction, reliability in practice is quite good.
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Re: Why pumps of coffee makers have that horrible noise « Reply #5 on: November 12, 2024, 02:16:37 AM » Author: Medved
Plus for the task I doubt that in the environment and water quality mechanisms like vane pumps would be reliable at all. From positive displacement systems, the pistons are the most robust concepts. And the vibration style is the simplest way to do it...
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Re: Why pumps of coffee makers have that horrible noise « Reply #6 on: November 12, 2024, 02:51:28 AM » Author: dor123
Water dispensers uses different pump which is much silent.
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Re: Why pumps of coffee makers have that horrible noise « Reply #7 on: November 12, 2024, 03:50:29 AM » Author: RRK
Well, OK, there is absolutely no need to reach 12bar in a water dispenser, so much less loaded and more silent pump is used.
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Re: Why pumps of coffee makers have that horrible noise « Reply #8 on: November 12, 2024, 08:09:08 AM » Author: Medved
Even the water dispensers may use the same concept of pump, but the fact for the water dispenser the pump is designed for barely few 10's kPa instead of the 1+MPa of the coffe maker would have huge impact on how loud the pump will be. 100x lower pressures means 100x smaller forces are sufficient and that could easily mean 40dB quieter operation and that is quite a difference.
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