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How to disable fan noisy Meanwell MP650
How to disable fan noisy Meanwell MP650
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Old 13th January 2018, 12:56 PM   #11
Nico Ras is offline Nico Ras  South Africa
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Originally Posted by nigelwright7557 View Post
That's shows a distinct misunderstanding of discos.
I often play to older crowds in pubs.
I am more retro than modern.
When you mention disco, all I remember bell bottom jeans, long pointed collar and cuffed shirts plenty of coloured drinks, many Bose 901's, racks of Phase Linear's and motown. Donna Summer, Gloria Gaynor, The Supremes, Temptations, Gloria Gaynor, MFSB, Love unlimited, Van Mcoy, Golden Earing.....
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Old 13th January 2018, 01:07 PM   #12
Nico Ras is offline Nico Ras  South Africa
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Meanwell included the fan sensing for safety reasons. Taking out the fan is the same as de-rating the PSU\. In that case you may as well replace it with a 100 watt PSU without a fan.

If you do what theAnonymous1 suggests then I would suggest to include a temperature sensing circuit that will control the fan speed automatically. This is not too difficult to do and won't have to worry about hearing the fan when playing at moderate levels.
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Old 13th January 2018, 01:24 PM   #13
taita is offline taita  Netherlands
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Originally Posted by johnnyx View Post
If the psu will not work without the fan, then the psu has a sense wire in addition to the fan power. Are there three wires to the fan?

Some fans have a pulse output that give an indication of rotor speed. Computer BIOS can display fan speed in some utility that some PCs have.

Usually, for industrial fans, a "stuck rotor" signal is all that is required. If the fan is seized, then a signal line is pulled high, so the monitoring circuit knows that there is a problem.

If the signal line is connected to the -ve fan connection, then it mimics the open-collector "fan ok" signal from the fan. It should run ok, but the protection is now disabled.
Indeed three wires to the fan. If I block the rotation of the fan the psu stops working. I have tried connecting the wires but didn't succeeded.

For home use the power consumption is very low. I've played for months with the fan in a separate box without any heating problems so I am not afraid of heating problems.
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Old 13th January 2018, 01:53 PM   #14
johnnyx is offline johnnyx  United Kingdom
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You need to know what the 3rd signal line does. Either look up the data sheet for the fan, or monitor the signal with an oscilloscope.
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Old 13th January 2018, 01:55 PM   #15
nigelwright7557 is offline nigelwright7557  United Kingdom
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Fans are usually 3 or 4 pin.
In 3 pin extra pin is PWM out.
In 4 pin extra pin is PWM in. (speed of fan)
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Old 13th January 2018, 02:04 PM   #16
Nico Ras is offline Nico Ras  South Africa
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I had a similar problem when I used a big 750 watt SMPS. It's fan came on full blast when powered up.

This drove me completely insane because it was very loud and made this PSU very unsuitable for audio until your thread here, which made me think....

It is a 3-wire fan and the third wire is used for sensing the fan run/not run. I had a look if this could be circumvented and found that injecting a square wave into that point tricked the PSU into thinking the fan was operating.

I generated a square wave from my sound card at about 100Hz via a 10K resistor into the test pin and the PSU fired up without the fan connected.

Although I would not suggest that you run the PSU under full load without a fan, this could be an interim solution to reduce the annoyance.
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Old 13th January 2018, 02:08 PM   #17
nigelwright7557 is offline nigelwright7557  United Kingdom
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I designed a temp controlled dual fan pcb using a PIC micro.
It has a thermistor to sense temp then adjusts PWM out to fan to suit.
This means fan is off when temp is cold and on when temp is hot.
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Old 13th January 2018, 03:59 PM   #18
taita is offline taita  Netherlands
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Quote:
Originally Posted by Nico Ras View Post
I had a similar problem when I used a big 750 watt SMPS. It's fan came on full blast when powered up.

This drove me completely insane because it was very loud and made this PSU very unsuitable for audio until your thread here, which made me think....

It is a 3-wire fan and the third wire is used for sensing the fan run/not run. I had a look if this could be circumvented and found that injecting a square wave into that point tricked the PSU into thinking the fan was operating.

I generated a square wave from my sound card at about 100Hz via a 10K resistor into the test pin and the PSU fired up without the fan connected.

Although I would not suggest that you run the PSU under full load without a fan, this could be an interim solution to reduce the annoyance.
Thanks for this contribution! I tested some things but just connecting one of the wires to the sensing one is not enough. The signal must have a pattern. Any ideas for generating a signal without a soundcard? I'm thinking of using the mains frequency?

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Old 13th January 2018, 04:12 PM   #19
nigelwright7557 is offline nigelwright7557  United Kingdom
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Originally Posted by taita View Post
Thanks for this contribution! I tested some things but just connecting one of the wires to the sensing one is not enough. The signal must have a pattern. Any ideas for generating a signal without a soundcard? I'm thinking of using the mains frequency?
You can buy silent or virtually silent fans.

I would be careful messing with mains especially as the power to the SMPS is full wave rectified from the mains so isn't relative to neutral line.
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Old 13th January 2018, 04:30 PM   #20
johnnyx is offline johnnyx  United Kingdom
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Minebea has 4 models in the series, two have locked rotor signsls of the type I discussed, and 2 have a tacho output;- 2410ML-04W-B79-B00 Specs and Media - DC Axial Fans - NMB Technologies Corporation

A NE555 timer chip could be used to give a signal to fool it into thinking the fan was present.

Cheap Chinese 555 timer PCBs are available, and could be used with suitable modification.

Last edited by johnnyx; 13th January 2018 at 04:37 PM. Reason: Additional info.
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