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Old Dec 14, 2011, 09:49 AM
KK4NZS
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Originally Posted by 376782 View Post
Thanks for your help Darren. Yes I did have separate 10 ohm resistors in the positive leads and the supply did shut down on fan failure. I am going to order a selection of 2 watt resistors in the 4.7 to 10 ohm range to see which works the best. I have scoped the output pulses form the fan speed lead and found it to be about 330 Hz. I hooked up my signal generator to the two white fan feedback leads and was able to keep the supply running without the fans installed not that I plan to do that. I may make up a small 555 timer circuit that I can adjust to that frequency to keep the supply running with slower fan speeds. If I do so i may also add a switch to allow the fans to run at full speed if I really want to draw some large load on the supply. When I get the time to try out the 555 timer I will let you know.

Dave
wow do you mind sharing some details on the circuit and great find...
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Old Dec 14, 2011, 10:20 AM
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Originally Posted by xandrios View Post
Hey jazz5000,

If you only want a single power supply then you may try the IBM xSeries 366 1300W PS.

It will supply 108.1 Amps at 12.2v(1318W).

The price is around 24.99 shipped.

http://www.ebay.co.uk/itm/IBM-39Y734...item53ea2300ea

This thread started by jj604 has all of the info you need on how to power them up.
Thanks i will probally go for that

Thanks for taking the time to search it.

So do i just connect the top right pin to ground and thats it?

Seems good

Thanks
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Old Dec 14, 2011, 10:31 AM
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Just ordered

Think im gonna stick around
One of the most helpful forums iv seen

and its a good excuse to get back into rc cars
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Old Dec 14, 2011, 10:38 AM
Steven
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Yeah. Just connect the top right pin to ground and It will power up.

The best price for 12v power in the UK that I can find.

Always good to help.
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Old Dec 14, 2011, 10:39 AM
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Cheers
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Old Dec 14, 2011, 08:02 PM
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Originally Posted by Nelapaty View Post
wow do you mind sharing some details on the circuit and great find...
I just tried out my 555 timer. It couldn't be a simpler circuit. It a basic astable oscillator and uses only 3 components plus the 555 ic so cost is less than a couple of buck and mounts on a vector board less than 1 sq inch. The timing components are 22k ohm resistor and .1uf capacitor. I would draw a circuit but don't really know how to do it using text. If you google the 555 astable timer circuit you will find all you need. There is lots of room to mount the timer internally. I connected the fans in series which really makes them pretty quiet compared to full speed. I plan to put a switch in to allow me to put the fans back to full voltage when I draw any significant load. I will post a picture when I get a chance.

Finally got around to provide some pictures and schematic of the astable oscillator. Refer to fig. 5-1a and change Rt to 22k ohm and Ct to .1uf and you should get approximately 330 Hz which is what the power supply is looking for with fans at full speed. I measured 333Hz with my scope. I disconnected both white feedback wires and connected them together to the output pin of the 555 timer. Negative 12 volts was taken off the copper bus tie between heat sinks but I used a solder lug under the screw as I believe it is important to keep these screws very tight. The positive 12 volts was taken off the output terminals. The circuit board was mounted to the copper bus tie with a small screw as you can see in the picture.
I have connected the fans in series without any resistors which has more than halved the fan speeds. I intend to install a DPDT switch to allow returning the fans to full speed if I am drawing any significant load on the supply. Future temperature readings with my IR temp meter will give me an idea of when this will be necessary. You can choose to use resistors in series with the fans if you chose as the power supply no longer cares about fans speed. The only caveat to this may be that if the power supply actually tries to control fan speed and looks for a different speed feedback then we will have a problem. If anyone runs into this problem please let me know.

Thanks,

Dave
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Old Dec 14, 2011, 09:49 PM
KK4NZS
Nelapaty's Avatar
Virginia
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Originally Posted by 376782 View Post
I just tried out my 555 timer. It couldn't be a simpler circuit. It a basic astable oscillator and uses only 3 components plus the 555 ic so cost is less than a couple of buck and mounts on a vector board less than 1 sq inch. The timing components are 22k ohm resistor and .1uf capacitor. I would draw a circuit but don't really know how to do it using text. If you google the 555 astable timer circuit you will find all you need. There is lots of room to mount the timer internally. I connected the fans in series which really makes them pretty quiet compared to full speed. I plan to put a switch in to allow me to put the fans back to full voltage when I draw any significant load. I will post a picture when I get a chance.

Dave
Ok I looked it up on google ASTABLE timer circuit generates a square wave but I found so many circuits very confusing any specific links would be nice..

Thankyou for your work..will work on it and see it if that does the trick.. for the fans you could install a fan speed controller nothing fancy ther's a bunch of controllers that are real cheap on ebay..

Thankyou

row
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Old Dec 15, 2011, 07:01 AM
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Do like Dan Rather, ask Kenneth!
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Old Dec 15, 2011, 05:15 PM
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Originally Posted by Nelapaty View Post
Ok I looked it up on google ASTABLE timer circuit generates a square wave but I found so many circuits very confusing any specific links would be nice..
how did you figure out the frequency

Thankyou

row
See post 1071

Dave
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Old Dec 19, 2011, 07:23 PM
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Well Dave....seems you didn't need my help after all. Turns out you are a quite proficent with them there electronics (more so than I) & are a bit of a mad scientist yourself. Lol! Right on.

Nice job, glad you were able to get things sorted as you desired and are able to share the specifics for others.

Darren
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Old Dec 19, 2011, 09:11 PM
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Originally Posted by extreme heli View Post
Well Dave....seems you didn't need my help after all. Turns out you are a quite proficent with them there electronics (more so than I) & are a bit of a mad scientist yourself. Lol! Right on.

Nice job, glad you were able to get things sorted as you desired and are able to share the specifics for others.

Darren
Thanks Darren. What we do to keep ourselves busy. I added a DPDT switch so that I can put the fans back to normal for high speed when I have a large load on the supply. If anyone needs a diagram of the switch/fan circuit I will see if I can add it to my pictures.

Dave
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Old Dec 20, 2011, 03:57 PM
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Sorry Darren!

Hi Guys,

Darren asked me to provide details on the circuit I made for him to emulate the fan pulse train. Needless to say, life kinda' took over.

I haven't had time to read the thread yet, but I am setting up a supply myself and hit this thread.

I will try to provide some details, but in a nutshell I used a 555 timer. The 555 output is not really suitable to tie directly to the fan sense line. The fan sense line appeared to have a weak pull-up, so I needed to provide a pull-low pulse. I did this by putting a diode between the output of the 555 (cathode - ) and the pulse sense line (anode + )
The design was a simple astable multivibrator design with a frequency of about ??? ok I can't remember off the top of my head...
Darren also needed a second pulse at an isolated supply. To maintain isolation, I used an opto isolator, the led side tied to the the 555 ouput with a resistor and the phototransistor side tied to the second supply fan sense and ground.

That is the basic idea anyway. I have to get to dinner and will read the thread later tonight...

Cheers,
Keith

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Originally Posted by extreme heli View Post
Sorry guys, no news yet, will post if I hear back with any details.

Dave are u using one single 2 Watt 10 Ohm resistor spliced inline to the positive lead for each of the fans? That’s 2 fans = 2 resistors per supply.

It should work without load when powering up no prob, but your charger should be pre-connected for regular operations otherwise you will trip it, or cause major unnecessary arcing, or damage charger, or all the above.

If hooked up correctly with a resistor to each of the fans and motherboard doesn’t like it, then try stepping up the speed a bit with a 2W 6.2Ohm or similar. The 10Ohm left mine right on the fine line of tripping an error, but kept chugging along. Manufacture tolerance differences may push yours over that line. If it won’t run with a 6.2Ohm then something is off from norm, or PS has changed how it reads an error.

I don’t make or program these things, all I am doing is sharing what has worked for me successfully. I can only imagine if you are having problems then it’s down to tolerance variations in resistors, manufacturing components, serial #, motherboard boundaries, input voltage....??

Be sure wiring is clean and not shorting out on anything & soldier inline even to test, don’t just touch or twist resistor in. Hope that helps.

Darren
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Last edited by DigitalDream; Dec 20, 2011 at 08:19 PM. Reason: remove incorrect PWM term reference after reading thread
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Old Dec 21, 2011, 10:55 PM
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Hey there Keith! Thanks for chiming in for those interested in the details of how you built my PWM emulator/generator. Still working flawless and your expertise is still much appreciated, & on that note I still owe you a few flights on my machine....when it warms up.

Well there you go fellas, a few more pieces to the puzzle straight from the horses mouth.

Darren
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Old Dec 22, 2011, 07:20 PM
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Hey Darrren!

So I will scope out a fan this weekend for the frequency I chose. That was our biggest issue. I was way over on our initial attempts.
I'll post the results on the weekend.

Cheers,
Keith

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Originally Posted by extreme heli View Post
Hey there Keith! Thanks for chiming in for those interested in the details of how you built my PWM emulator/generator. Still working flawless and your expertise is still much appreciated, & on that note I still owe you a few flights on my machine....when it warms up.

Well there you go fellas, a few more pieces to the puzzle straight from the horses mouth.

Darren
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Old Dec 22, 2011, 08:54 PM
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Originally Posted by DigitalDream View Post
Hey Darrren!

So I will scope out a fan this weekend for the frequency I chose. That was our biggest issue. I was way over on our initial attempts.
I'll post the results on the weekend.

Cheers,
Keith
Hi Keith;

Not clear whether you are looking for a slower fan that would output the same frequency feedback pulses or plan to use your 555 IC to emulate the feedback signal. If you do find slower fans that output the same frequency (approx. 330 HZ) let me know. At the present I have disconnected the feedback and replaced it with the 555 CCT as in post #1071. The fans are connected in series to run much slower and can be selected to high speed with a DPDT switch.

Dave
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