PWM to Analog converter circuit

Ok So I have mine running now with 2 Corsair SP120 Performance Edition mounted on my Matterhorn Pure.

After an initial problem which turned out to be a fail-safe option in my BIOS it's working spot on.

Even though the fans are running 300rpm more than the original Alpenfohn single fan, it's quieter. I've adjusted my PWM control using ET6 and using the medium setting on the adaptor it's settled at a little over 1100rpm @ 30°C (Ambient: 24.1°C). Bear in mind that these fans will max at almost 2400rpm @ 12v.

I haven't tried a stress test yet but I will do soon, but I do know the medium setting on the adaptor with PWM @ 100% duty cycle pushes the fans to just under 2300rpm which is almost max speed at which point my PC sounds like a TurboProp winding up for takeoff. :D
Tealc - I know I quoted different figures in my email earlier, I've tweaked ET6 some more since then :)

I would like to openly thank Tealc for taking the time to design and build the adaptor and for all the support he gave when I couldn't get it to work correctly, which again I will state was an issue with my BIOS settings and not the adaptor.

SP120Matter.jpg


Ignore the cheap generic exhaust fan, it's temporary. It's getting replaced with an AF120 soon
 
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That's great resident!
Using 2x TY-143 fans. Idle is set to 750rpm (because northbridge chip need the air to stay below 57c) with ET6 setting of 40% @ 40c and 100% @ 60c. Core temp is 37c ambient 26c. Core temp stays same with idle at 670rpm (ET6 set 10% @ 25c and 100% @ 60c) but northbridge goes to 60-64c.

Changed motherboard couple days ago from EX58-UD3R to X58A-UD3r rev. 2. Had blue covers off of board chips on EX58 and didn't pull them on X58A before install. With covers off northbridge was 44-49c @ 670rpm. Don't think it was fan change as TY-140 & TY-143 are same except TY-143 goes to 2500rpm.. and color :)
 
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doyll said:
That's great resident!
Using 2x TY-143 fans. Idle is set to 750rpm (because northbridge chip need the air to stay below 57c) with ET6 setting of 40% @ 40c and 100% @ 60c. Core temp is 37c ambient 26c. Core temp stays same with idle at 670rpm (ET6 set 10% @ 25c and 100% @ 60c) but northbridge goes to 60-64c.

Changed motherboard couple days ago from EX58-UD3R to X58A-UD3r rev. 2. Had blue covers off of board chips on EX58 and didn't pull them on X58A before install. With covers off northbridge was 44-49c @ 670rpm. Don't think it was fan change as TY-140 & TY-143 are same except TY-143 goes to 2500rpm.. and color :)
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I have an 'issue' on my board with what AIDA identifies as MCP

gigabyte_ga-m68mt-s2p_rev.3.1.jpg


It's the heatsink with Gigabyte written on it near the SATA.

It was shooting to around 50°c seconds after startup so I found out an old little chipset fan. Problem is the GFX card fan housing gets in the way so I've had opt for an Antec 80mm Spot positioned in a way to flow air over the area. The plus side is that it also helps to shift heat away from the GFX card too.
 
Mine is the one between PCI slot and CPU socket. Down airflow cooler puts air into big opening side but cross airflow cooler kinda misses is. Remove the top cover so it looks like yours and it gets airflow.

Sorry Tealc for hijack.
 
A little update anyway.

I might have already mentioned that I was looking at incorporating a trimmer/potentiometer into the circuit so I don't have to spend hours fiddling with resistors trying to get the right balance of power going into the circuit.

Well I think I've found a solution. I managed to find a potentiometer that can handle 0.5W or roughly 40mA of current at 12v.

Here it is next to another one with less than a third of the power handling. The blue potentiomter is a 5k 0.5W 25 turn potentiometer.

P1050301.jpg


Why is this important?

It is through this adjustment that I can give such good speed regulation throughout duty cycle. Without it I am stuck with whatever setting I hard wire in. A change in fans or power cannot be easily adjusted for and compromises have to be made.

There are three spots in the circuit where I can use a potentiometer to affect the power the fan uses.

1) Next to the fan itself. A potentiometer/rheostat would have to be at least 6W or more and they get very expensive, really expensive.

2) On the incoming PWM signal. I tried this and it worked up to 1 Amp but gives far too much opportunity to destroy the mosfet if someone fancies dialling it up. The mosfet got super hot. I could step it up to a large power mosfet of course but they are £1 to £2 each.

3) In the middle between the N channel mosfet and the PNP transistors. I already use resistors here so this is a logical place to start.

So this is designed to go in the middle.

So I wired a new circuit up with the transistors moved around a little and the potentiometer on the leading edge, so it could stick out the end of the heatshrink.

P1050314.jpg


P1050316.jpg


I was able to go back easily to the 5 hole wide design and now the circuit uses less resistors, has no switch and cannot be damaged by sitting in a non switched dead area of the switch location.

Here's a video. I haven't done a video for ages.


This video goes through the setup process for a few different configurations from 4 fans at 0.55A down to 1 single fan.

The circuit revision is good for fans from 0.1A to 0.55A and can be adjusted to suit individual needs. It's just a matter of dialling down the duty cycle to 20 or 30%, adjusting until the speed you want is on the fan and it's good to go. Simple. Ok maybe not as simple as a switch but it's so much easier to build.
 
I watched this video when you first uploaded it and the V2 looks great - can adjust the circuit for any fans and not just the ones it was originally designed for :)
 
Wow. I'm blown away with V2.

I know you said in the video that running one fan the potentiometer may not go low enough to run it down to 5v.

What if there were an optional adaptor similar to the 12>~7v ones that come with some fans? Obviously it'd mean the top end would be trimmed aswell but I wouldn't think that would be too significant would it ?

I might be talking nonsense tbh but it was just something that popped into my head.
 
Resident said:
Wow. I'm blown away with V2.

I know you said in the video that running one fan the potentiometer may not go low enough to run it down to 5v.

What if there were an optional adaptor similar to the 12>~7v ones that come with some fans? Obviously it'd mean the top end would be trimmed aswell but I wouldn't think that would be too significant would it ?

I might be talking nonsense tbh but it was just something that popped into my head.
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Thanks to you both.

In answer to your question Resident. I don't need an adaptor at all. :D

Cast your mind back a while where I posted the following image derived from a little test I did with a bunch of different current ratings and a lower rated potentiometer and plain resistors.

ohmsvscurrent.jpg


The resistance (given by the potentiometer) to current to the fan forms a non-linear scale. At high power a slight turn of the knob results in a big change of power, yet at the low power end of the scale a slight change has a very small change in power. You may have noticed me turning the screw loads on the last couple of fan segments, whereas at the beginning it was just a couple of turns.

Instead of 5k potentiometers I just use 10k potentiometers, or 15k or whatever. I would have thought 5k would be enough but as we are dealing with non linear components nothing ever works the same between different components. So this first batch of 4 pots was just a test. I think I will probably send off for some 10k ones from Hong Kong. They'll still be fine for the 0.55A or higher uses, but the adjustments will be slighter again and possibly be 1 turn instead of 2 turns.

These potentiometers are amazing though. They give such awesome fine control. Fiddling with my older trimmers to set a voltage was tricky indeed as you try and turn the dial half a degree.
 
Your knowledge and skills keep amazing me.

As you know I'm running 2x front intake, 1x bottom intake, 1x rear exhaust and 2-3x cpu fans on CPU PWM fan socket with Akasa/Gelid PWM splitters.

I've just installed 2x TY-143 700-2500rpm fans on CPU. I still need to replace the TY-140 bottom intake with a TY-143 to balance airflow to CPU fan demands. In this way airflow is from bottom up through passive HD 5770 GPU into CPU cooler and out top with all of these fans running same control/speeds.

Rear exhaust fan helps keep airflow over motherboard to cool it.

My problem is the 2x front intakes on CPU PWM are running too slow to keep HDDs cool. As a result I have been playing around with them at fixed speed instead of running in PWM circuit.

I need the 2x front intakes to run faster at low CPU fan setting to keep HDDs cool and increase as GPU/CPU heat rises to supplement airflow to GPU/CPU.

Any suggestions on how to keep the front fans idle speed up while still using PWM signal? They are Akasa FN053 fans.
 
Well Doyll you could use a PWM converter dialled a little high so that they don't slow down all that much.

Would react something like the blue High trace in this graph.

Resident-final.jpg


With a Version 2 you could set it at say 1000 RPM at your idle duty cycle and it would speed up to 1500 by about 50 or 60 duty cycle.

I think this is the beauty of this solution. It's just so adjustable.

Other options would be to use a microcontroller to double PWM duty cycle or perhaps use an Op-amp with a low pass filter to add some gain to the PWM voltage, but unless you use an expensive precision Op-amp you lose the top end voltage.

Forgetting about PWM you could use a temperature based fan to react directly to the heat of the hard drives. I'm not sure how configureable they are and whether they just react to a predefined range of temperatures, which may not be suitable for hard drives. Again with things like thermistors and LM35 type devices it's relatively easy to get an output of temperature but not so simple to get a configureable reaction to temperature unless you use microcontrollers or a lot of discrete components.

The simpler temperature fans will use a transistor, a resistor or two, maybe a capacitor and a thermistor. All of these will be selected to suit the attached fan's specifications but wouldn't necessarily work across other fans.
 
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Maybe one of your Phanteks adaptors would be overpowered enough to drive the fan at higher RPM at a low duty cycle. The 140mm Phanteks are actually 0.26A at 12v and the FN053 are rated 0.18A according to Akasa so should run pretty fast. For an idea of where the fan will actually power my Apache PWM which is a similar speed fan, which is rated at 0.35A actually uses just 0.11A at 12v, and 0.12v if I add some load to the blades. It might use a bit more at startup though.

It generally doesn't matter to a PWM fan if it's driven at less than 12v, although I have heard that some don't like it.


Or maybe a circuit that takes the PWM signal, checks it against a reference voltage and does the following:-

1) If lower than reference, then use it's own PWM generator to send to the fan with 50% minimum cycle.

2) If higher than reference, use CPU PWM and feed it right through to the fan.

I'm thinking something with a 555 timer and a comparator. Would be a bit of a fiddle but might be a fun project.
 
So got a new breadboard the other day and decided to have a fiddle with the circuit a bit to experiment with the gain. The original circuit has the PNP wired up in a certain way that isn't maximising the gain of the transistor so I wired up the breadboard so that I can see the difference between the two ways of wiring it up.

P1050328.jpg


Solderless breadboards are really useful for experimenting with circuits as you can easily add in components, change values and swap stuff around.

P1050340.jpg


The heatsink I've shoved on the B772 is super effective.

P1050343.jpg


With the B772 at the back it's the old circuit and with it at the front it's the experiment.

P1050345.jpg


In the video I just have a look at the differences, add and remove fans and stuff. The differences are quite suprising.

I can drive over an 1 Amp with the new configuration, albeit with a larger voltage drop of around 1.2v from 12v across all fans. The losses are just the way things are with transistor circuits. The heat generated by the PNP is undoubtedly where the voltage loss in going. At 0.1-0.4A loads the losses are less than 0.5v but when they get up to 1 Amp they go over the 1v level. This is typical of fan controllers of course, unless you have a super duper Buck converter type thing going on.




In the next video I swap out the 235 Ohm and blue 5k pot for a 1k Ohm and a 22k trimmer to experiment with the range of fans the circuit can handle with the new configuration.


With this trimmer in place the circuit can now handle 70mA to over 0.5A of fans and is more adjustable than I thought it might be using just a 270 degree trimmer.
 
mikeclueby4 said:
Hey Tealc, nice work there! Any chance you can post a schematic for your V2?

Other readers in the thread might also be interested in my super-KISS version at http://forums.overclockers.co.uk/showthread.php?p=22644791 - lots of limitations but I describe them in the thread. I totally understand if Tealc's solution appeals more to you =)
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Sorry but I wouldn't bother with your version at all, choosing Tealc's for the following reasons:

1. It retains the RPM feedback meaning that you don't have to faf about with BIOS settings & you can still monitor via software which makes it easier to set power curves in Speedfan/ET6

2. V1 and V2 both have adjustability, V1 less so but both can be adjusted to suit a number of conditions

3. Multiple fan support on one adaptor. The one Tealc made for me supports 3 fans. IIRC Tealc has managed upto seven on V2.

4. Power for the fans is directly sourced from the PSU rather than the fan header so no worries about overloading fan header.

5. Tealc makes the adaptor with the proper connectors. No need to rob bits from your case. Also he heat-shrinks the entire board which means the 'heatsink' isn't able to short out on the case/other components.
 
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Thought I'd already posted a schematic beyond that MS word one, which to be fair is very close to the end result anyway and should be close enough for anyone to work out what's going on. V2 simply has a variable resistor in series with a 300 Ohm ish resistor instead of the 10k (I think it was 10k) between drain of the BS170 and base of the B772. V1 had a switch doing the variable resistance.
 
Resident said:
Sorry but I wouldn't bother with your version at all, choosing Tealc's for the following reasons:
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Yep, like I said, totally understand! Lots of benefits to Tealc's solution! (Not to mention me NOT offering to solder mine up for people! :cool: )

I just wanted quick-n-dirty DIY myself because I didn't need more for this project, and offered up the results for anyone interested.

I won't be bringing it up again in this thread; don't worry :)
 
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