5 wire fans?

[NiHaoMike]

Yesterday, I was working on a Dell rack server and I had to remove the fan assembly in the process. I noticed that the Nidec fans had 5 wires - red, black, green, blue, and yellow. I was told that the fifth (green?) wire has to do with static pressure detection, which presume is done in the inverter DSP. Has anyone else come across a 5 wire PC fan?

 

[EarthDog]

Just in a server.. a Dell server like you.

Thideras and I were chatting about this and he came up with these links. Now, they are for desktops it seems so it may be apples to oranges but its worth a look anyway...?

http://pinouts.ru/Motherboard/dell_fan_pinout.shtml
http://pinoutsguide.com/Motherboard/dell_5pin_4pin_pinout.shtml

SPressure sure doesn't seem like it though.

 

[NiHaoMike]

Not just a 5 pin connector, there actually were 5 wires going to the actual fan motor assembly.

 

[Aldakoopa]

Yeah that's a new one. I rewired a 5 pin connector on a Nidec I pulled from an old Dell to work in a regular fan header but there was still only 4 wires.

 

[NiHaoMike]

What I know is that if the airflow was restricted, the fan immediately revs up, much faster than you would expect from thermal time constants. I once read an article (back when so called digital "ECM" motors were just becoming common) that the DSP inside can actually detect the airflow by sensing the torque the motor is applying and then using some algorithm to calculate the static pressure based on the torque at a given RPM. My guess is that the fifth wire just sends that calculated static pressure back to the host machine so it can issue a maintenance alert if the airflow starts becoming restricted due to dust.

 

[Bobnova]

Tap into that wire with a scope and see what it's up to.

 

[NiHaoMike]

The server has already been returned to the engineers who were doing some software work on it. I did think to scope the signal, but I didn't have enough free time.

 

[Silver_Pharaoh]

What else did you expect from Dell?
lol they make up their own standards to follow sometimes.

Like those "atx" connectors on some PSUs

 

[NiHaoMike]

It's worse than that - I have yet to come across a Dell rack server that used ATX (pinout) PSUs. Though to be fair, HP doesn't either.

 

[ATMINSIDE]

It's worse than that - I have yet to come across a Dell rack server that used ATX (pinout) PSUs. Though to be fair, HP doesn't either.

On server equipment I see that as a good thing.
It keeps people from using a random POS power supply as a replacement.

 

[Bobnova]

I'd guess it's more towards cost cutting and efficiency. The ATX20/24P connector dates back from the 5V heavy days, count the number of 5V wires compared to the number of 12V wires, then consider how much runs off 12V (all the heavy stuff) vs 5V (RAM, sometimes, and.... yeah that's about it).
No need to have all that extra wire and consumed space on a server rig where space and airflow are at a premium.

The only >4P fans I've seen personally had 4 wires that actually went to the fan and a 5th wire that looped between the two remaining pins on the 6P connector as a presence detect type thing.
That's the Nidec BetaV that goes into some HP Prolient servers.
5 wires into the fan itself is an odd one.

 

[Automata]

As Bobnova said, they don't run normal power supply connections for airflow and space reasons. They used (Poweredge R510) to run something similar, and the extra wiring is annoying and gets in the way if you have to replace something. In that picture, you can see they are using a ton of 12v, ground, and a few 3.3v lines. No 5v. You can see the difference comparing it to the R710, which is a substantially different configuration and saves a lot of space for other components.

 

[magellan]

5V isn't even useful for the chipset anymore? Say, the PCH, BIOS, serial/parallel ports or ethernet interface?

 

[Bobnova]

Nope, that's all 3.3v, 1.8v, or lower.
Very little runs on 5V directly these days. Mostly just microcontrollers, and only the more legacy-ish MCUs, or those that are built to run direct off a LiPo.
The "BIOS" is an EEPROM or flash chip, they're typically 3.3v. They use a couple milliamps though, so a linear regulator from 12v is fine.

Serial and parallel ports are sort of gone. Serial is +/- ~12v though anyway.
Ethernet has a charge pump and/or buck/boost regulator(s) built into it, as it is a +/- voltage signaling format as well.

PCH runs 1.x V, as the BIOS screens will tell you.

 

[RnRollie]

you know what *might* still be using 5V on the MB? Some LEDs or those "bootcode" LED/LCD displays...
And of course all your USB ports still use 5V