Help placing an on/off switch between PSU & HDD

T

TOOzeroSICKz

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Jul 31, 2005
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I have an external USB HDD that I only turn on to backup data and have always wanted it in my computer case to save space, but I didn't want it on all the time. Then, I read an article on a 3 way switch between hard drives which gave me an idea to have it mounted in my case and plugged in via sata and power, but have a switch wired in the power cable to turn it off/on whenever I want.

I'm not experienced in the electrical area and was wondering if this DPDT switch would work if I hacked the power cable? http://www.newark.com/c-k/f2uoa/pushbutton-switch/dp/49H6697

From what I understand, I would just have to connect the 5v and 12v cables to terminals 1-2 on the switch and the switch would then function between 0-1 and 1-2 and leave the grounds going straight to the HDD.
 
In short terms, yes. However not all switches are created equal. What I would recommend is a DPST switch instead, as you don't need 2 "ON" positions. It's always a good idea to double check the switch itself for function with an ohm-meter before actually connecting it... I doubt your power supply would thank you if you connected the 12v to the 5v line by accident. :) And yes, leaving the grounds connected but disabling both the 12v and 5v line with the switch will work.
 
One _major_ flaw in that article you're referring to is that it _will_ nuke your HDD at some point when the +V lines are connected prior to ground (black wires). Grounds should be connected before V+ gets connected, that's why the SATA power connector is 'staggered', i.e. the ground lines on the connector are longer than the other lines, ensuring that ground is always connected before the other lines. This is what makes hot-plugging possible. You seem to understand this already, but I just wanted to make sure :)

I'm not sure whether the system/Windows needs to supports hot-plugging (not all SATA adapters support this!), which is something you may want to check before you turn the HDD on while the system is running.
 
I'm not sure you have your terminals sorted out right. You want the 12V and 5V from the PSU to go to the "0" terminals, and then have wires go from the "1" terminals to the 5V and 12V lines which feed the drive. So current comes from the PSU12V line to the left "0" terminal, out through the left "1" terminal, and to the drive. Similarly for the 5V line, except on the right-hand side. A DPST switch would also do the trick, as Logan321 stated.
 
So with the DPST I would connect the 3V from the PSU to 1 and 3V out to 2 and 12v in to 3 and 12v out to 4 while leaving the grounds straight to the HDD?

This was the DPST and diagram I found:
Circuitry:DPST
Contact Voltage AC Max:125V
Contact Current AC Max:10A
4566393.jpg

httpwwwfarnell.jpg



Thanks for the help and suggestions.
 
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