Semi-Pre-Mod External HDD power adapter conundrum!

[Hobbyist83]

Hi,

I have an old external hdd power adapter.. which i would like to use as a low voltage bench supply.

Input: 100-240v 1A

Output: 12v 2A / 5v 2A

Now the question is... I would like to max the voltage by connecting both the 12v/5v outputs together to potentially output 17v.. now the question is.. is this actually possible or would the end result.. set the smoke alarm off?! If it doesn't set the alarm off, would i be able to use a buck boost converter to up the voltage further or would i just be better off using one of the outputs for the buck-boost?

Your view and help would be greatly appreciated.

 

[Gryd3]

Hi,

I have an old external hdd power adapter.. which i would like to use as a low voltage bench supply.

Input: 100-240v 1A

Output: 12v 2A / 5v 2A

Now the question is... I would like to max the voltage by connecting both the 12v/5v outputs together to potentially output 17v.. now the question is.. is this actually possible or would the end result.. set the smoke alarm off?! If it doesn't set the alarm off, would i be able to use a buck boost converter to up the voltage further or would i just be better off using one of the outputs for the buck-boost?

Your view and help would be greatly appreciated.

Wow! Don't do that ever!
Think of Voltage as 'pressure', connecting the 12V and 5V wire together would result in pushing the difference back down the throat of the 5V side of the supply.

May I ask why you want a higher voltage?

 

[Hobbyist83]

I am working on a project which involves 2.5/3.5" SATA HDD's (5v/12v respectively) being run by a Raspberry Pi (5v)

I am wanting to design it so that it can power both the Pi and HDDS and switch the voltages automatically depending on the drive type connected! Additionally all running off 5v via Buck Boost.

Unless I am missing the fact that the SATA PWR connector has both voltages connected?! :S

Complete NOOB.. Apologies!

 

[Gryd3]

I am working on a project which involves 2.5/3.5" SATA HDD's (5v/12v respectively) being run by a Raspberry Pi (5v)

I am wanting to design it so that it can power both the Pi and HDDS and switch the voltages automatically depending on the drive type connected! Additionally all running off 5v via Buck Boost.

Unless I am missing the fact that the SATA PWR connector has both voltages connected?! :S

Complete NOOB.. Apologies!

The power supply for computer HDDs, present both the 12V and 5V supply to the drive. They don't actually 'combine' the voltages.
You can use it to power both devices, but the 5V 2A may not be able to drive both under heavy load.
Simply splice another wire on the 5V line for the pi

 

[Hobbyist83]

5v 2A
-
-
BUCK BOOST 12v - - - - - - - - - BUCK STEP 5v ----------------------------------Pi
- _
- -
- -
---------------------<--------------<------
_
_
SATA PWR

Would this work as this is the idea that i have come up with?!

 

[Gryd3]

5v 2A
-
-
BUCK BOOST 12v - - - - - - - - - BUCK STEP 5v ----------------------------------Pi
- _
- -
- -
---------------------<--------------<------
_
_
SATA PWR

Would this work as this is the idea that i have come up with?!

yeah... but it would be so much better just to use a more capable 5V supply...
Sometimes a switch-mode supply switches the negative rail which can cause issues.

 

[Hobbyist83]

"A more capable 5v supply?" as in a higher amps?

Did some searching and found normal average operating AMPs for the Devices most likely to be connected.

A. >700 to 1000 < mA = Pi
B. >250 to 400 < mA = 2.5 Sata
C. >500 to 1500 < mA = 3.5 Sata
D. >450 to 470 < mA = Pi Touch Screen

now taking the higher values equates to 3.410mA (3.5A)

Would i be able to take B out of the equation and have 1.970mA (2A)* as I would assume value C would be able to support both itself and value B depending on which drive is connected at the time.


* As for using a 2A power supply would be easier and cheaper than finding a rare 3A.

 

[Gryd3]

"A more capable 5v supply?" as in a higher amps?

Did some searching and found normal average operating AMPs for the Devices most likely to be connected.

A. >700 to 1000 < mA = Pi
B. >250 to 400 < mA = 2.5 Sata
C. >500 to 1500 < mA = 3.5 Sata
D. >450 to 470 < mA = Pi Touch Screen

now taking the higher values equates to 3.410mA (3.5A)

Would i be able to take B out of the equation and have 1.970mA (2A)* as I would assume value C would be able to support both itself and value B depending on which drive is connected at the time.


* As for using a 2A power supply would be easier and cheaper than finding a rare 3A.

The Pi can take up to 1A. A 3.5 Sata drive according to your table could take up to 1.5A. If you use these things, you just sent over your limit.
Otherwise, you can use a 2.5 Sata, Pi and Pi Screen and be JUST BARELY under the 2A limit for 5V.
It's not hard to get a more capable supply... Most cell phone chargers can output more than 2A. While a 3A might be 'rare' you can always look for bigger. The voltage is the most important part here... and if you are willing, you can use an old desktop computer power supply. They provide well over 10A for the 5V wire.

In any case. What are you trying to build? There are all sorts of options, share details and we can help pick an ideal solution.

 

[Hobbyist83]

The idea that I am trying to prototype is a raspberry pi driven portable sata hard disk drive sanitation device (quite the mouth full).

It would would from a 5v source which is then split. A 5v rail to a buck boost converter to create the 12v rail for the 3.5.. and then a split from the 12v rail to buck step down to create a 5v rail to power the Pi with Screen in addition powering the 2.5 drive.. which both sata power rails goto a sata.. female connector and the DATA connection only uses the DATA+/DATA- which to a usb port on the Pi.

by using something like this.. and i did find a 3A charger.

http://www.ebay.co.uk/itm/5V-3000mA...597276?hash=item25a7a8089c:g:KtYAAOSw3KFWb9O-

The portability of the idea is the focal point.. and trying to make it as light as possible so a PSU wouldn't really work.. but a buck boost/buck step would be more suitable.

although saying this.. even though they do not make 12v 3a plug top adapters.. I may compromise in and use something this..

http://www.ebay.co.uk/itm/For-12V-3...934701?hash=item2a302dce2d:g:cSYAAOSwiLdV-pNp

and been rummaging around and found a hdd external psu and the output is 12v/5v 3A(3A).. would this work??

 

[Gryd3]

The idea that I am trying to prototype is a raspberry pi driven portable sata hard disk drive sanitation device (quite the mouth full).

It would would from a 5v source which is then split. A 5v rail to a buck boost converter to create the 12v rail for the 3.5.. and then a split from the 12v rail to buck step down to create a 5v rail to power the Pi with Screen in addition powering the 2.5 drive.. which both sata power rails goto a sata.. female connector and the DATA connection only uses the DATA+/DATA- which to a usb port on the Pi.

by using something like this.. and i did find a 3A charger.

http://www.ebay.co.uk/itm/5V-3000mA...597276?hash=item25a7a8089c:g:KtYAAOSw3KFWb9O-

The portability of the idea is the focal point.. and trying to make it as light as possible so a PSU wouldn't really work.. but a buck boost/buck step would be more suitable.

although saying this.. even though they do not make 12v 3a plug top adapters.. I may compromise in and use something this..

http://www.ebay.co.uk/itm/For-12V-3...934701?hash=item2a302dce2d:g:cSYAAOSwiLdV-pNp

and been rummaging around and found a hdd external psu and the output is 12v/5v 3A(3A).. would this work??

I think you need to take a step back and clearly outline your requirements and limitations.
Portable... yet requires you to plug it in the wall...
I would strongly suggest you get a 12V source, then use a buck converter for the 5V supply.
12V and 5V to the HDD, and the 5V to the pi, you do not need more than one converter unless your power supply is something other than 12V or 5V.
As far as current is concerned, you will need to oversize it based on the largest requirement you think you will encounter.
Although... the part that I find curious is the feasibility of the project to begin with...
SATA are almost exclusively 'internal' devices, and alternatively are housed in either portable enclosures that include a power supply, or a drive caddy for use in hot-swap capable bays.

 

[Hobbyist83]

Well if it works it works.. if it blows up in my face.. at least i tried.. and the Raspberry Pi runs off 5v which is a portable machine with a 5v source and can support primarily a 2.5" under its own power or 3.5" (with the 3.5" drives external adapter). I am trying to implement both.. in to a singular package.. its just a project.. tinkering around and seeing if its actually possible!

The inspiration is from http://www.johandraaisma.nl/raspberryproject/ and trying to expand the idea and make it in to a smaller package with additional options.