[fan] More control over HDR fan

[BMAX]

I don't know if the following might help, I wrote it some time ago but never got round to posting it.

"I have been monitoring the HDR-FOX T2 for some time and found, as many others have commented, that the behaviour of the cooling fan is somewhat strange. Just to refresh our memories, nothing seems to happen until after a temperatue level (54C?) is exceeded, whereupon the internal fan starts at full speed, with an associated obtrusive noise. As the temperatue falls, the fan speed reduces in steps, until the temperature falls below 49C, where upon the fan stops. There is invariably an undershoot of several degees, and then the cycle begins again. This seems to be a back to front operation to me.

The observed method of operation results in a see-saw temperature profile with a period of about one hour. I remember from my product qualification days, that temperature cycling is a recognised method of accelerating early electronic component failures during product life testing, albeit using somewhat larger temperature differentials. Hence, I have looked for an alternative method of cooling.

I mounted a twelve volt 3" computer fan via a reduction tube (made from a scrap pieces of plastic gutter down spout), over the case outlet of the existing fan. The fan is powered from the 5v supply available at the USB port, which is only present when the unit is powered up. This produces a continuous gentle, almost completely silent, air flow through the unit, whenever it is powered up.

The result is that the box temperature rises over a period of about an hour to about 20C above ambient and then stabilises. The internal fan never comes on, but of course it is still available in the unlikely event that the temperature should ever riseto 54C. I have had this running for several months and the highest disc temperature I have seen is 45C, which was 19C above ambient.

I consider that the lower operating temperature together with the absence of temperature cycling can only be beneficial for the performance and life of the product. There is also an adequate margin as demonstated by the recent high ambient temperatures and, of course, it does not involve any modification to the box itself."

 

[Ezra Pound]

As stated in #20 I think the fan may need to start on Full just to get it going, but there is no reason to keep it on full after the initial start-up. The current temperature cycling looks like this :-

 

[Black Hole]

We won't know for sure until we get some experience. PWM is pretty good at overcoming the usual problems with brushed DC motors (if not filtered to a smooth DC first), and brushless motors manage these things in the internal controller (three wires: power, ground, control). Is the fan two-wire or three-wire?

 

[af123]

My theory is that Humax designed it to be as silent as possible for as much of the time as possible. If the fan doesn't come on until the temperature reaches 55 then for most boxes that means that it can wake up, record for an hour and then go back to sleep without the fan ever coming on. On my box, high fan level usually only lasts for two or four minutes too.

I don't think it's great for the disk though. I'm sure that if you look at your disk attributes on the webif diagnostics page you will see FAILING NOW or IN THE PAST against the failed column for disk temperature. Remember that the determination of a temperature failure is made by the firmware on the disk, so effectively the disk manufacturer.

 

[af123]

Package on its way up and should be available shortly.

I can barely hear mine at 50% so I'll see how that changes HDD temperature this evening.

If you have humaxtv debugging enabled (diag debugtv) then you will see status messages in /tmp/humaxtv.log relating to the fan control.

 

[Wallace]

We won't know for sure until we get some experience. PWM is pretty good at overcoming the usual problems with brushed DC motors (if not filtered to a smooth DC first), and brushless motors manage these things in the internal controller (three wires: power, ground, control). Is the fan two-wire or three-wire?

The fan is three wire. I have already replaced one.

 

[Kev_w]

Annoyed that I'm away this weekend - looking forward to geeking around with this!

Out of interest; do we know if the standard fan speeds changed with newer firmwares? Mine is definitely louder than it used to be (could just be my fan getting old).

Sent from my GT-N7100 using Tapatalk 2

 

[af123]

With the speed at 50% HDD temperature is definitely better.

 

[af123]

Out of interest; do we know if the standard fan speeds changed with newer firmwares? Mine is definitely louder than it used to be (could just be my fan getting old).

I have only spent any time analysing 1.02.32 so don't know the answer to that. I'm not aware of mine being any louder than it has ever been.

 

[Wallace]

If you set the fan speed at 50%, for example, and the disk temperature rose to 55deg, would the fan still speed up as if you hadn't installed this package or would it be fixed at 50%?

I appreciate that this is less likely to happen if the fan is constantly on, even at 50%.

Edit. Ah. This fixes the MINIMUM fan speed, so the fan could potentially speed up if/when the Humax FW calls for it to. Have I understood that correctly?

 

[af123]

If you set the fan speed at 50%, for example, and the disk temperature rose to 55deg, would the fan still speed up as if you hadn't installed this package or would it be fixed at 50%?

I appreciate that this is less likely to happen if the fan is constantly on, even at 50%.

It would still speed up. The package (currently) only applies a minimum speed. Any time the standard software wants a higher speed than is set it will get it.

At 50% I can still hear mine but it isn't intrusive. The occasional clicks from the disk are louder (and I don't have the TV on at the moment, just the Humax). I suspect the sweet spot will be different for different units depending on the hard disk and the environment.

 

[Wallace]

Thanks for the reply. The penny dropped for me after I have posted the message, but thanks for confirming.

 

[Ezra Pound]

Wiki Notes added HERE, I think this will be another popular package.

 

[af123]

For completeness:

A restart is required after package installation or upgrade but subsequent minimum fan speed changes can be done on the fly (with a lag of up to two minutes). I'm also updating the sysmon package to better reflect the fan states in the temperature graph.

 

[prpr]

With mine set at 25% last night, the cycle period was nearly double what it was before. With it at 33% it is almost a flat line (heat out = heat in).
Do we think the fan life will be shortened by running it constantly? Is disk life going to be lengthened by having it at a more constant temperature?
Which is better?
Could the fan package measure the disk temp. and cause the fan to come on at a lower temperature (and speed) than the Humax software does? Then the fan would get rid of the heat before it could exceed the disk's "too high" threshold, not be on too long nor be too noisy and we would have the best of all worlds?

 

[Ezra Pound]

Could the fan package measure the disk temp. and cause the fan to come on at a lower temperature (and speed) than the Humax software does? Then the fan would get rid of the heat before it could exceed the disk's "too high" threshold, not be on too long nor be too noisy and we would have the best of all worlds?

I think what is in place already does this, I guess the only other way of reducing total fan 'revs' would be to have the fan utility kick-in after a timed delay

 

[xyz321]

With mine set at 25% last night, the cycle period was nearly double what it was before. With it at 33% it is almost a flat line (heat out = heat in).
Do we think the fan life will be shortened by running it constantly? Is disk life going to be lengthened by having it at a more constant temperature?
Which is better?
Could the fan package measure the disk temp. and cause the fan to come on at a lower temperature (and speed) than the Humax software does? Then the fan would get rid of the heat before it could exceed the disk's "too high" threshold, not be on too long nor be too noisy and we would have the best of all worlds?

Personally I would rather it ran at a stable, relatively cool temperature rather than cycling up and down near the fail limit. A setting of 50% works for me with an ambient temperature of around 20ºC. The HDD temperature stabilises around 40ºC.

My old 9200T had a slow running fan which ran continuously (even in standby) and did not fail in over 5 years.

 

[xyz321]

I think what is in place already does this, I guess the only other way of reducing total fan 'revs' would be to have the fan utility kick-in after a timed delay

A delay would increase the initial temperature gradient and tend to cause localised hot spots. This may cause more stress to the HDD components.

 

[Ezra Pound]

. . . cycling up and down near the fail limit . . .

I don't think the normal set-up of the fan turning on at 55Dec C is near the fail limit for the hard drive, (Pipeline state 75Dec C as the maximum operating temperature), although the fan is obviously also keeping the electronics cool as well. I do think keeping temperature cycling to a minimum is desirable, but unless you intend to keep the Humax running 24/7 it can't be avoided

A delay would increase the initial temperature gradient and tend to cause localised hot spots.

I don't think there would be any harm in delaying 'fan on' time until the hard disk reached, say a few degrees below the operating temperature you intend to stabilise at, this would still stress the components less the Humax is doing at present

 

[xyz321]

I don't think the normal set-up of the fan turning on at 55Dec C is near the fail limit for the hard drive, (Pipeline state 75Dec C as the maximum operating temperature), although the fan is obviously also keeping the electronics cool as well. I do think keeping temperature cycling to a minimum is desirable, but unless you intend to keep the Humax running 24/7 it can't be avoided

The smartctl utility report will show a temperature fail if the firmware in the drive determines that the temperature is over the manufacturer's fail limit. I think the limit is set at 56ºC. If it has failed previously, it will be reported as "In_the_past" in the "when failed" column.

I don't think there would be any harm in delaying 'fan on' time until the hard disk reached, say a few degrees below the operating temperature you intend to stabilise at, this would still stress the components less the Humax is doing at present

I agree it would stress the components less than at present but we have the opportunity to reduce the stress even further so why not go for it. At a setting of 50% the sound is not noticeable. The wear and tear on the fan should be minimal particularly as it is running at a low constant speed.