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      07-02-2021, 01:58 PM   #1
Jagaer
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DIY - Server Power Supply for Coding

Since the car is getting up there in both years and kms, I've had to work on it a fair bit more than before, necessitating the use of INPA. After suffering through another FRM issue due to low power, I decided to pick up a proper power supply.

However, the $300-$700 prices for a proper power supply seemed a bit pricey for what amounts to regulated 14V power. (MST-80 or Schumacher INC-700A)

A number of other people have had success repurposing server grade power supplies as a dedicated power source. These offer a few benefits:
  1. Inexpensive
  2. High Amperage
  3. Efficient

First, the completed product:





As a Canadian, we are on 120V supply, so this power supply will max out at 75A@12V (64A@14.2V). For those of you living in 220V nations, it will allow the full 100A@12V (85A@14.2V)



Reference sources:

HP DPS-1200FB A HSTNS-PD11 13.8v mod -

BMW DIY Power Supply for Programming (HP Server PSU Conversion) -


Hardware:
$40 - DPS-1200FB from Kijiji
$25 - LCD Digital Display Multimeter (6.5-100V, 0-100A) - https://www.amazon.ca/gp/product/B01..._title_o00_s01
$5 - Round Rocker Switch
$16 - 8AWG Booster Cables - https://www.canadiantire.ca/en/pdp/m...-0111212p.html
$5 - 8AWG Wire Lug Ring Clamps ($5 per pair)
$0 - Old Electric Stapler blow molded case
$0 - Solid Core wire (Different Colours)

$91 - Total

Solder a 22k Resister between Pins 33 and 32. A number of references show to just solder a 1k resister between pins 36 and 33, but those pins are wired to weak pull-up or pull-down circuits, so essentially you're fighting between them.



Open up the power supply, the edge circuit board controls adjustment and monitoring.



We need to solder 75k and 15k resistors to change the regulation circuitry. By default, the Pot will not adjust high enough and the Over Voltage Protection (OVP) will not allow you to set a 14V output. I didn't have 75k and 15k resistors, but 82k and 18k were close enough to allow me to set the desired voltage. (Note the electrical tape placed between the resistor and circuit board to avoid short circuits. I seem to have misplaced my kapton tape...)





Adjust the pot to get your desired output, I set it to 14.2V, note that this Voltage will drop with a corresponding increase in Amperage.



I cut a 1m length of booster cable to wire from the power supply to the clamps. I chose 1m as the booster cables are only 8awg, you can get a larger gauge of cable, but that makes it considerably harder to work with & solder.

The SPST rocker switch is simply set up to complete the circuit between pin 36 and ground. This will turn on/turn off the 14V output.

Zip ties are used to hold the circuitry in place. Zip ties in the top half are loose, in order to allow the wires connecting the top and bottom half to move as the lid is closed.

A hole was cut in the side to allow the power supply fan to vent hot air





Usage Notes:
--- When connecting the power supply, TURN THE POWER SUPPLY ON BEFORE CONNECTING IT TO YOUR CAR. I have not set it up to protect against return path (Car battery powering the power supply), and have not fused it for short circuit!
--- The fan will still run, as power is still connected to the power supply. This is ok
--- It takes ~20 seconds for the power supply to de-energize the circuits (Capacitors to discharge). Don't touch the clamps together or put the clamps down until the volt meter shows you that you can.



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      01-02-2022, 03:52 AM   #2
GovernUrMental
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Excellent DIY! Thank you
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      01-03-2022, 09:56 AM   #3
Andystobbs
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That's a great idea. The price of off the shelf supplies is ridiculous for what they are.
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      01-03-2022, 10:40 AM   #4
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I did this with a 1200 watt PC supply.

It works great.

A standard PC supply of 750w or more will work just fine.
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      01-17-2022, 06:22 PM   #5
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Fantastic DIY. Possibly overkill for most but a great idea, nice job!
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      01-18-2022, 01:42 PM   #6
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Rushing thru aliexpres rn hahah. Thank you so much.
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      08-12-2022, 03:43 AM   #7
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Hi can you confirm for the 22k resistor, itís pins 36 and 37 as pictured and not 32 and 33 in the notes?
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      08-13-2022, 01:13 PM   #8
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Quote:
Originally Posted by Steveo View Post
Hi can you confirm for the 22k resistor, itís pins 36 and 37 as pictured and not 32 and 33 in the notes?
"Solder a 22k Resister between Pins 33 and 32. A number of references show to just solder a 1k resister between pins 36 and 33, but those pins are wired to weak pull-up or pull-down circuits, so essentially you're fighting between them."
Read this again and you will get the point
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      08-14-2022, 07:46 AM   #9
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Quote:
Originally Posted by evominati View Post
"Solder a 22k Resister between Pins 33 and 32. A number of references show to just solder a 1k resister between pins 36 and 33, but those pins are wired to weak pull-up or pull-down circuits, so essentially you're fighting between them."
Read this again and you will get the point
What does ďweak pull-up or pull-down circuitĒ mean?
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      08-17-2022, 03:12 PM   #10
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Iíve tried with a 76k and 15k resistor and canít get above 13.8v adjusting that single pot.
Any ideas?
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      08-18-2022, 06:51 AM   #11
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Had to use a 76k and 11k resistor in the end to get to 14.2v output with a 220v supply in U.K.
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      09-19-2022, 06:17 PM   #12
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Quote:
Originally Posted by Steveo View Post
Had to use a 76k and 11k resistor in the end to get to 14.2v output with a 220v supply in U.K.
Hey man, could you provide me with more info how did you do it? I am also living in Europe with 220V wall power. You replaced the 15k resistor with 11k, right? Did you solder them the same as the OP picture? Where did you solder the 22K as I still don't get which is pin 33/36 etc. from which side they are counted? The last thing is about the rocker switch and in between where it is soldered? Thanks!
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      09-20-2022, 09:55 AM   #13
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I almost started building this. But found a used power supply for $100 14.5v 50A and bought it. Guess my point is there are options out there, if someone finds a project like this a bit challenging.
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