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DIY Voltage Controlled Scalable PWM Controller - Page 4

post #31 of 76
Quote:
Originally Posted by IT Diva View Post

The real advantage of PWM is that it preserves the torque at less than max rpm speeds.

That means a PWM fan or pump can and will start from off at very low speeds, and can run at lower speeds than its undervolted counterpart.


Here's why: (at slight risk of oversimplification)

Fans or pumps do not draw more current when you reduce the voltage, as the voltage drops, the current drops proportionally, and the actual power level drop is a square relationship.

To use some simple numbers, let's take a pump, and at 12V it has a 2 amp draw, that's 24 watts and see what happens as we drop the voltage . . .

Reduce the voltage to 6 volts, and the current will drop to 1 amp, which gives 6 watts

half the voltage . . .half the current . . . . 1/4 the power


Now lets see what happens if it's a PWM pump:

12V with a 100% duty cycle, the same 2 amp draw, and the same 24 Watts of power

Now reduce the duty cycle to 50% . . . . 12v at 2amps, that's 24W, but for half the time during each pulse interval, so effectively 12W

That's twice the actual power to the pump at 50% duty cycle as at half the voltage.

That's why PWM has better torque at lower speeds, and allows things to run slower and therefor quieter than variable voltage control.


Pumps and fans designed for PWM control have advanced motors and onboard electronics to implement it, so there is no additional "noise".


Trying to use a pulse modulated supply voltage to effect speed control over fans or pumps not designed to be controlled that way is another matter al together.

You can get all manner of garbage going that route.

The PWM control standard for PCs is for a 25KHz frequency, that's a pulse every 40 microseconds.

Cheaply made, low parts count, PWM generators have a terrible tendency to shift frequency considerably lower as the pulse width shortens to effect slower speeds. and worse, not all started at the 25KHz spec.


Once they shift low enough to be into the audio range, you'll get that "buzzing" which is the fan or pump tuning on with each pulse.


Adding length to resistive sensors has no effect, as long as the connection is secure, solder is the best.

Sensors are nominally 10,000 Ohms at about 24C ambient. The resistance of the wires would be in the thousandths of an Ohm per foot.

It would take hundreds of feet of the relatively small gage wire used for sensors to effect a single degree of error.

Twisted splices, on the other hand, will end up being a nightmare.


Hope that all helps,

Darlene

yes it dose and I will answer and ask more questions when laptop is charged and I am of better mind, in Singapore and having a few drinks getting ready for my next flight!
post #32 of 76
Quote:
Originally Posted by WiSK View Post

Quote:
Originally Posted by givmedew View Post

Yeh I experienced that buzzing/rattling with the bigNG fan controller in PWM mode.

What she is doing is awesome though... I only run PWM fans and pumps now and would love a little more control since right now I am limited by the single CPU tied PWM signal that my board outputs the other PWM is off the motherboard temp which is useless. Which means I have to run the same exact PWM signal to all my fans and my pump.

As far as I recall, the bigNG modulates the 12V signal and doesn't even have a connection for the fourth PWM wire. There is really a dearth of true PWM fan controllers. Zalman's ZM-MFC controllers offer one PWM connection, and the rest are voltage controlled. The Aquaero 5 also has a single PWM header. Apart from that I don't know of any more, so you're often indeed stuck with what your motherboard provides.

One trick if you are watercooling, is that with a fullcover block, you have a spare PWM connector on the GPU. Unfortunately it's got a kind of mini connector, but Gelid makes an adapter for this. Thanks to this I'm using my GPU to control my pump, and the two PWM headers on the motherboard to control push and pull fans independently.

Thanks for the info on the adapter. As for the bigNG yes you are correct but what I was saying is that I had noises like that while it was in PWM mode which isn't PWM but it is called that on that controller. It is very annoying... have not had the problem with my motherboard though.
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post #33 of 76
Quote:
Originally Posted by IT Diva View Post

It's not exactly a 2 second answer . . . .

I'm guessing that you have measured the speed control pot on the fan's speed control at 10K, and want a way to replace it with something a fan controller can control?


The best way to do that would be with a digi pot and a PIC microcontroller chip.

It would take some circuitry, a PIC programmer to program the microcontroller chip, and someone to write the program.


Basically, there's no easy way, and I don't offhand know of an IC chip that performs that function.

Darlene

Thanks, that's all I really needed to know. Searched the webs a bit and there are programs available for the micro controller. Think I'll manage from here (with some help of my roommates biggrin.gif)
post #34 of 76
Thread Starter 
Little Update;

And from the "land of No Good Deed Goes Unpunished",


I finished up a soldered perfboard version for testing, and with my old generic fan controller, everything was perfect, so I plugged up to the new Lamptron CW611 . . . . .

Crap, . . . . . test fans wouldn't change speed in manual and no PWM output


Then it dawned on me that maybe Lamptron has designed this new high output controller similarly to their FC9, whereby the + output to the fan/pump is referenced to the +12V rail of the PSU, and it is actually the negative output to the fan/pump that is being controlled to rise above the negative PSU rail to effect voltage control at the controlled device.

Yep, sure enough, that's the case, so a bit of design modification was called for.

The goal here is for the design to be able to accommodate either type of controller, so it will be jumper block selectable on the prototype here to interface to a negative rail referenced controller or a +12 rail referenced controller.


I made some changes to the protoboard version to test with, and it works fine with the 611.

I'll be implementing the changes into the soldered perfboard version today, and should be able to plug up the D5's for live testing by tomorrow.


Here's some pics of the soldered up version;

It's a two board assembly, where the top board has all the interface connections and input voltage manipulation, and it plugs onto the lower board that performs the actual PWM signal generation and manipulation.


The interface connections are as follows:

Far right upper pigtail is the PSU molex connector for power

Far right lower pigtails (2) are power out molex's for D5 pumps

Next left top and bottom pigtails are 4 wire connectors for 35X pumps, or the PWM and tach connector on D5 pumps

Next left top pigtail is the 4 pin connection to the mobo CPU fan header with just the gnd, tach, & PWM wires used

Next left lower pigtail goes to the fan controller output . . . with a short adapter/extension to be able to work with both positive rail and negative rail referenced controllers.





Here's a close up of the lower board:




And the upper board with the pigtail connections easier to see:




The jumper blocks work as follows:

Rightmost top sends the tach signal from the pump connected to the upper connector to either the mobo or the fan controller

Rightmost lower does the same thing for the pump connection

Next left upper selects whether the PWM out to the pumps comes from the mobo, or from my controller

Leftmost lower selects either manually controlled, or fan controller referenced PWM output from my controller . . . . This jumper would be replaced by a switch in an installed version, but it's just easier to use the jumper on a prototype.


Darlene
post #35 of 76
Thread Starter 
Meaningful Update . . . .

Yeeeeeeeeeeeeeee Haaaaaaaaaaaaaaa . . . . . It Works with the CW611.


Not quite as perfectly as it does with ground rail referenced variable voltage outputs, but quite well, for not doing a whole redesign.

I solved the issue of how to hook it up to a Gnd rail referenced controller versus a +12V rail referenced controller by having 2 separate connection cables, 1 for +12V rail types (FC9 and CW611), the other for Gnd rail types.

I also added a jumper block to select normal output to use with Gnd rail ref'd controllers or inverted output for +12v rail ref'd controllers.

Without the inverted output for controller like the 611, things speed up when they should slow down and vice versa.


Anyway, everything plugs up as planned and works very acceptably.

I need to make some trim adjustments yet to tailor the output to match up to the D5's PWM curve, but it's pretty close.


Here's a few pics:


Darlene









Edited by IT Diva - 5/30/13 at 7:17pm
post #36 of 76
Thread Starter 
Woooooo . . . . Hooooooooo . . . .


My little creation is ready for prime time. wheee.gifwheee.gif


I added some new circuitry today to better interface with the Lamptron controllers that have the output referenced to the +12V rail, and a little tweak to solve a quirk in the 611 that's not present with the FC3 I use to test with.

I made the new circuitry as an onboard module that plugs in between the analog voltage output controller and my PWM controller when using a Lamptron type variable voltage output fan controller.

I'll post some pics and do some more write up on it tomorrow.


Darlene


I also tested the flow meter function, and liked that it reads out in LPH or GPM, user selectable. Sooooo much easier than having to look at a conversion chart for milliliters per minute to GPM that's required when using a fan rpm readout with the Koolance flow meters.
Edited by IT Diva - 5/31/13 at 9:12pm
post #37 of 76
Awesome! thumb.gif
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post #38 of 76
Thread Starter 
Pics as promised;

Darlene


Here's the original lower board for reference:




And here's the updated version:




With a close up of the new circuitry:




I also determined that having the power wires in the 4 pin fan connector pigtails was overly redundant, so I removed them which made them much less cumbersome so the top board is a bit more manageable now also.

I'll put up a new topside pic of it tomorrow, as it's currently drying after a few coats of clear lacquer to seal it and keep the copper side from oxidizing and corroding.



Edited by IT Diva - 6/1/13 at 6:24pm
post #39 of 76
Darlene I just sent you a PM about all this. Need some help, lol. Bless my heart.
 
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post #40 of 76
Thread Starter 
Rev 2 is here with increased user friendliness and a stand-alone manual controller, primary board layout;


Couple of quick pics with a write-up and more pics to follow as soon as I get the protoboarded primary board, onto a soldered up perfboard.


Darlene






Edited by IT Diva - 6/9/13 at 7:22am
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