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'[EE] Papst fan tacho signal'
2010\07\03@061141 by KPL

picon face
I'm building a controller for computer cooling fans, that is using
their tacho signal to find out if it's running. It's starting with
very shallow pwm pulses and increasing them until detects fan running
with stable rpm. Then speed can be changed via serial port.
I have tested it with few fans and blowers I had on hand and it was
working good. Tacho signal was as expected, open-collector output, I
just had to add 10k pull-up to +5V.

I have a lot of used 127mm PAPST fans taken from some older (about
year 2000) equipment, that are in good working order, but I can not
figure out what kind of signal tacho gives out. It does not show any
pulses if connected to scope directly, it does not show anything when
connected to same pull-up resistor.
I could not find a data sheet for this model, W2G115-AD17-22.

Any ideas, what kind of signal that could be?
--
KPL

2010\07\03@143056 by Spehro Pefhany

picon face
At 06:11 AM 7/3/2010, you wrote:
>I'm building a controller for computer cooling fans, that is using
>their tacho signal to find out if it's running. It's starting with
>very shallow pwm pulses and increasing them until detects fan running
>with stable rpm. Then speed can be changed via serial port.
>I have tested it with few fans and blowers I had on hand and it was
>working good. Tacho signal was as expected, open-collector output, I
>just had to add 10k pull-up to +5V.
>
>I have a lot of used 127mm PAPST fans taken from some older (about
>year 2000) equipment, that are in good working order, but I can not
>figure out what kind of signal tacho gives out. It does not show any
>pulses if connected to scope directly, it does not show anything when
>connected to same pull-up resistor.
>I could not find a data sheet for this model, W2G115-AD17-22.
>
>Any ideas, what kind of signal that could be?

Some fans have an output alarm signal rather than a tacho signal.

Typical is high for normal operation, low for under speed, open
collector. Often it is suppressed during start-up.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spam_OUTspeffTakeThisOuTspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com



2010\07\03@145819 by Philip Pemberton

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flavicon
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On 03/07/10 11:11, KPL wrote:
> I have a lot of used 127mm PAPST fans taken from some older (about
> year 2000) equipment, that are in good working order, but I can not
> figure out what kind of signal tacho gives out. It does not show any
> pulses if connected to scope directly, it does not show anything when
> connected to same pull-up resistor.

There are a few possibilities:
  1) It's a "Variofan", and that line varies the fan speed
  2) That's an alarm output. Stall the fan (shove a screwdriver between
the motor support and the blades and power up) and see what that line does.

If it's not giving you a speed-feedback signal and you want one, you
could always put a piece of foil on the back of one of the fan blades
and use an IR sensor to detect it.

If you don't fancy the added hardware, put the fan into a
current-sensing circuit. Fan -ve goes to ground via a 1R or 10R resistor
(depending on how much current the fan pulls and how much "burden
voltage" is acceptable). Feed the output of the -ve/resistor junction to
an opamp threshold detector (or use a dual opamp -- amplify the signal
to 0V/5V, then feed it to a comparator).

There was something along these lines published in EPE's "Ingenuity
Unlimited" column a few years back (most likely pre-2001). "Fan Failure
Alarm" or something like that. IIRC it used a transistor amplifier and
an R/C time-delay circuit -- the R/C junction was pulled to ground by
the transistor, and also drove another transistor to produce the "fan
OK/failed" output.

--
Phil.
.....piclistKILLspamspam@spam@philpem.me.uk
http://www.philpem.me.uk/

2010\07\03@160048 by KPL

picon face
>
> There are a few possibilities:
>   1) It's a "Variofan", and that line varies the fan speed

No, text on fan says "+ red -blue sensor white" which corresponds to
the colors of the three wires. Fan speed changes with changing
pwm/voltage nicely.

>   2) That's an alarm output. Stall the fan (shove a screwdriver between
> the motor support and the blades and power up) and see what that line does.

Just tried that, line is still 0.
I'll try a different fan from the same equipment, since I noticed the
one I am using has to work in 18-30V range, not 12V that I am feeding
it now. Probably that could cause a problem.
The other one is 12-30V. Unfortunately the only fans of that type that
I have here are currently cooling the PC I am typing on:)

{Quote hidden}

Yes, I know there are other ways to detect rotation, but the main idea
was to build a controller usable for any fan with tacho wire, to avoid
any adjustments and calibrations.

--
KPL

2010\07\03@171015 by Philip Pemberton

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On 03/07/10 21:00, KPL wrote:
>>    1) It's a "Variofan", and that line varies the fan speed
>
> No, text on fan says "+ red -blue sensor white" which corresponds to
> the colors of the three wires. Fan speed changes with changing
> pwm/voltage nicely.

Um... that sounds like a Variofan to me. "Sensor" would be the little
thermistor the fans come with.

> Yes, I know there are other ways to detect rotation, but the main idea
> was to build a controller usable for any fan with tacho wire, to avoid
> any adjustments and calibrations.

A peak/trough detector and a couple of opamps would eliminate the need
for any 'adjustments or calibrations'...

--
Phil.
piclistspamKILLspamphilpem.me.uk
http://www.philpem.me.uk/

2010\07\04@041823 by Richard Prosser

picon face
The Papst fans that I have used with pulse speed feedback have used an
open collector output. You need to add a 10k or so pull-up resistor to
get a pulse output. I think we used a 5V supply for this (not the 12
or 24V main fan supply voltage).

RP

On 4 July 2010 09:10, Philip Pemberton <.....piclistKILLspamspam.....philpem.me.uk> wrote:
{Quote hidden}

>

2010\07\07@170125 by Barry Gershenfeld

picon face
One problem with PWM'ing a 3-wire fan is that the tach signal gets chopped
up, reflecting the PWM on the supplied power.

You and I could imagine a hold-up circuit for the tach signal, but
apparently most fan makers can't.

2010\07\08@023259 by KPL

picon face
I was using a cap as a simple filter, so fan itslelf got actually DC.
All smaller 3-wire fans were working fine, I could see perfect square
tacho pulses, no problem there.

Now I have read (microchip AN770 and documents for TC642) that fans
have actually to be driven by very slow PWM, 60Hz or less. I had dig
up all docs I could find from papst, and could not find any exact info
on that from them.
I found that the two kinds of papst fans I have, have different kind
of "third wire" - one has white wire, which should be DC 0-10V control
input, but the other has yellow wire, which had to be ordinary open
collector tacho signal. Docs show that I have to use a pull up
resistor there, which i did, but did not get any signal there, anyway,
just zero.
Even more, I tried to find out signal path on one of original
controller boards, that came with the fans, and it looked like the
yellow wire is used that way, that 4-layer board was not easily
traceable without desoldering components, though, so I can be wrong.
Just the resistors around that signal wire were much larger than I
would expect, in hundreds of kilo-ohms range.
I tried to partially duplicate that, and did not get any better result anyway.

Basically I am stuck with that problem, and seems I'll have to
completely redesign that controller, to work with current sensor and
not using tacho line at all. There are useful descriptions for that
approach in above mentioned microchip documents.

I just want to use those fans, since they are excellent mechanically,
and, after all, I have a lot of them, for free :)


On Thu, Jul 8, 2010 at 12:01 AM, Barry Gershenfeld <gbarry42spamspam_OUTgmail.com> wrote:
> One problem with PWM'ing a 3-wire fan is that the tach signal gets chopped
> up, reflecting the PWM on the supplied power.
>
> You and I could imagine a hold-up circuit for the tach signal, but
> apparently most fan makers can't.

--
KPL

2010\07\08@052436 by Richard Prosser

picon face
KPL,
I'm not sure which type of fan you are trying to get going - the type
with the speed control wire, or the type with a pulse/tacho output or
a third type with a temperature sensor.

If the fan is the type with the speed control wire, this fan can be
driven from a constant DC supply (12V etc,) and the control voltage
derived from a filtered  pwm signal. In this event, the input
impedance of the control circuit is likely to be quite high, so to get
a smooth control voltage, the resistance  value of the RC filter could
be reasonably large values iso as  to minimise the capacitance size
required. It would not, in this case, be necessary to PWM the main
supply to the fan.

Just using a capacitor to filter a pwm supply voltage can lead to
extra difficulties as the load "resistance" - the load seen by the
filter - will change according to the drive level and this may upset
the smoothing characteristics of the filter - or effect the response
speed..

Hope this assists

Richard P

On 8 July 2010 18:32, KPL <@spam@kpl.listesKILLspamspamgmail.com> wrote:
{Quote hidden}

> -

2010\07\08@070729 by RussellMc

face picon face
> Even more, I tried to find out signal path on one of original
> controller boards, that came with the fans,

1. Are you able to run the fans using an original controller and look
at the signals with a scope?

2. If you have many fans which are otherwise not useful you could
dismantle a fan to see what the wiring does.

Fan is liable to be less complex than controller board and less liable
to be  4 layer PCB.



                 Russell

2010\07\08@072102 by KPL

picon face
On Thu, Jul 8, 2010 at 2:06 PM, RussellMc <RemoveMEapptechnzTakeThisOuTspamgmail.com> wrote:
>> Even more, I tried to find out signal path on one of original
>> controller boards, that came with the fans,
>
> 1. Are you able to run the fans using an original controller and look
> at the signals with a scope?

Unfortunately not quite. Those modules came from complex units (GSM
base stations) that have internal bus with about 60 pins. I do not
think I can find out their functions...

>
> 2. If you have many fans which are otherwise not useful you could
> dismantle a fan to see what the wiring does.

That's a good idea actually, thanks.
Fans are not quite useless, since they run very well, I just want to
slow them down predictably and detect failures.

>
> Fan is liable to be less complex than controller board and less liable
> to be  4 layer PCB.
>

--
KPL

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