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Old Jan 16, 2012, 08:03 PM
ancora imparo
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Melbourne, Australia
Joined Jul 2005
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OK just to be a total pedant that's not why they are called switching power supplies.

They are called switching power supplies (more properly Switching Mode Power Supplies) because the power transistors inside switch at high frequency. Effectively they convert the incoming AC to DC then switch it at high frequency (where the necessary control and conversion components can be much smaller) to convert to the required voltage, then rectify it back to stable DC for the charger.

Takes pedant hat off - forgive me.
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Originally Posted by TheWoodCrafter View Post
+1

That is why they are called switching power supplies.
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Old Jan 16, 2012, 08:04 PM
AMA #535918
USA, NV, Las Vegas
Joined Apr 2006
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For all you cheapskates out there, I stumbled on 2 Poweredge 2650 supplies for $4.99 + $12 shipping. The supplies are 41 amp @ 12v.

I plan on putting them in series. I've taken the warnings under advisement. I appreciate those offering information. In this case in particular, a little knowledge is a dangerous thing.


http://www.ebay.com/itm/Lot-2-Dell-P...ht_3388wt_1193
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Old Jan 16, 2012, 08:15 PM
RC Helicopter Pilot
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United States, CA, Westminster
Joined Mar 2010
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Quote:
Originally Posted by vegasbs View Post
For all you cheapskates out there, I stumbled on 2 Poweredge 2650 supplies for $4.99 + $12 shipping. The supplies are 41 amp @ 12v.

I plan on putting them in series. I've taken the warnings under advisement. I appreciate those offering information. In this case in particular, a little knowledge is a dangerous thing.


http://www.ebay.com/itm/Lot-2-Dell-P...ht_3388wt_1193
WOW!!
That is 2 power supplies for $4.99.
So with shipping for $22 you can have 24V at 1000WATTS.
Crazy.
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Old Jan 16, 2012, 08:21 PM
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Originally Posted by jj604 View Post
feather made a good point to me off line. These PS MAY rely on fans built into the housing they slide into. That is they aren't actually fanless but the fan(s) not part of the PS itself but external.

Anyone familiar with these Poweredge systems in practice and know if this is true?

I must say cooling a 1700Watt supply without any forced air flown seems unlikely.

John
I could be wrong here .. but seems to me that you are only cooling any drops across devices at the rated current, which wouldnt add up to 1700W .. A lot of that power is across the load .. That doesnt mean that the drops and inefficiencies of the supply wouldnt develop enough heat to still need cooling fans. Remember its a switching supply, not a linear / pass transistor type supply .. Its one of the main advantages of a SMPS in that its very efficient and doesnt generate nearly as much heat..

Randy
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Old Jan 16, 2012, 08:29 PM
ancora imparo
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Melbourne, Australia
Joined Jul 2005
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Absolutely correct. You couldn't cool 1700 Watts with a small fan. That's a lot of heat. What you are cooling is the 1700 x efficiency of the power supply lost energy.

So if the supply is 90% efficient that's about 170 Watts at full load current.

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Originally Posted by N2CUA View Post
I could be wrong here .. but seems to me that you are only cooling any drops across devices at the rated current, which wouldnt add up to 1700W .. A lot of that power is across the load .. That doesnt mean that the drops and inefficiencies of the supply wouldnt develop enough heat to still need cooling fans. Remember its a switching supply, not a linear / pass transistor type supply .. Its one of the main advantages of a SMPS in that its very efficient and doesnt generate nearly as much heat..

Randy
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Old Jan 16, 2012, 10:13 PM
Use the 4S Luke
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Joined Aug 2003
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vegasbs - you should be able to isolate the output of one of those.
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Old Jan 16, 2012, 10:31 PM
AMA #535918
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poweredge 2650

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Originally Posted by feathermerchant View Post
vegasbs - you should be able to isolate the output of one of those.
I've done a lot of research and pretty sure it will work. If not, I know where to get some. I've been to your site a lot recently.

I'll be using these instructions:

So, to isolate the negative pole from the chassis it is necessary to isolate three mounting bolts by adding a plastic washer between the printed circuit board and the chassis posts and another between the bolt head and the printed circuit board, on each of the three bolts shown on the pictures. Use plastic bolts on 1 and 2.

For reference, here is the connection for the back pin connector in order to make the power supply turn on. Simply connect the pins marked Y together:

N N N N N Y
N N N N Y N
N N N Y N N
N N N N N N


But then I found the attached picture. It shows a different way to power it on.
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Old Jan 18, 2012, 09:53 AM
KK4NZS
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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.

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
Wooohooo it works it works the circuit works..
I finally had some time to get this thing done and it works like a charm its putting out 13.6 without any fans (not for long offcoursecouple of seconds ) now I just have to test it with a load and see what happens.
update Just checked with a 61.6amp load and its holding well @ 13.07volts yea baby finally Breakthru

Thankyou guys for some awesome work Dave your'e the bomb.


Row
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Old Jan 19, 2012, 04:50 PM
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Does anyone know how to adjust the voltage up on the DELL AA23300 and the DPS-500 CB ??? I need to get as close to 13.8 VDC as I can .. Sure would be nice to have schematics for these power supplies .. Theres a small surface mount pot on the DPS-500 but it only gets me up to 12.7 VDC .. Cant find any adjustment for the AA23300, so assuming I would have to replace a part or put a resistor in parallel or some such thing ..


Thanks in advance ..

Randy - N2CUA
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Old Jan 19, 2012, 09:19 PM
Once u go yak u never go back
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Erie, PA
Joined Mar 2005
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Quote:
Originally Posted by vegasbs View Post
For all you cheapskates out there, I stumbled on 2 Poweredge 2650 supplies for $4.99 + $12 shipping. The supplies are 41 amp @ 12v.
]
Quote:
Originally Posted by TheWoodCrafter View Post
WOW!!
That is 2 power supplies for $4.99.
So with shipping for $22 you can have 24V at 1000WATTS.
Crazy.
ummm. Math check. $4.99 plus $12 = $16.99 shipped not $22. Just bustin 'em for ya TheWoodCrafter. Just havin' some fun.



.... and yes I just bought two for no other reason than I like to tinker. Feathermerchant has turned me into a power supply glutton.
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Old Jan 19, 2012, 09:21 PM
RC Helicopter Pilot
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Originally Posted by marksextra View Post
ummm. Math check. $4.99 plus $12 = $16.99 shipped not $22. Just bustin 'em for ya TheWoodCrafter. Just havin' some fun.
I guess I figured 4 PS by mistake.
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Old Jan 19, 2012, 10:17 PM
Once u go yak u never go back
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Erie, PA
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Originally Posted by TheWoodCrafter View Post
I guess I figured 4 PS by mistake.
That a boy. You're mind was thinkin' "MORE POWER" subliminally.
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Old Jan 20, 2012, 04:10 PM
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Originally Posted by xandrios View Post
Full pinout for Dell Poweredge 2800, 2850, Dell AA23290, Dell 7000814-0000, Dell NPS700AB PSUs.

Connect PS On and PS Kill to ground to power up.

Pin B2 may be a spare or for fan control. Check by connecting B2 to ground.
FYI this pin out also works for 7001452-J000 Z750P-00 Power Supply.
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Old Jan 20, 2012, 04:28 PM
ancora imparo
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Melbourne, Australia
Joined Jul 2005
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Guys, if you find a solution to a PS that isn't listed in the sticky thread here

http://www.rcgroups.com/forums/showthread.php?t=1292514

can you please post a link to the solution in the sticky.

I can't keep up with all these different numbers.
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Old Jan 20, 2012, 06:06 PM
Once u go yak u never go back
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Erie, PA
Joined Mar 2005
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Originally Posted by jj604 View Post
Guys, if you find a solution to a PS that isn't listed in the sticky thread here

http://www.rcgroups.com/forums/showthread.php?t=1292514

can you please post a link to the solution in the sticky.

I can't keep up with all these different numbers.
Will do..btw. thats the best thread. Thanks for keeping it up.
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