1. FroceMaster

    Thread Starter Member

    Jan 28, 2012
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    4
    Hi
    have a little plan to make a Sata switch. Like i have 7-8 disk on a controller. And want to be able to switch between them.
    The power will i use a normal relay. But what shuold i use to the 4 data lines ? Reed relay or ??.

    I will just disconnect the harddisk in win. And then power off the disk and switch to next disk. Hotswap
     
  2. wayneh

    Expert

    Sep 9, 2010
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    I don't understand the need for any switching. Why not use a port multiplier and just perform hot swaps?
     
  3. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
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    Well then i will fysical disconnet the drive by the wire.
    Besides a port multiplier sets the transfer speed down to sata150 not 300 or 600.
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,126
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    Says who?

    Perhaps you can diagram your setup. I don't know why'd you want to switch anything.

    But, you could switch the 4 data lines as long as the power and ground lines are already handled. Since SATA supports hot swapping, throwing the switch should not be different UNLESS the device has a problem with power and data lines not switching at the same time as it would in a hot swap.
     
    Last edited: May 28, 2015
  5. ian field

    Distinguished Member

    Oct 27, 2012
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    The last motherboard I upgraded to actually has more SATA ports than I need for that PC. The PC where I store all the downloaded stuff only has 2 plus 2 more on a RAID card that simply acts as a SATA expansion because I didn't do the RAID setup.
     
  6. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Just turn on and off power to the drive. No need to touch data lines.

    Sudden power off is probably bad for the drives, but... they will last few hundred (or more) power on/off cycles so who cares.
     
  7. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    Schematic later .maybe tomorrow
     
  8. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hi,

    You may have a problem using normal relays as they are not made for high speed signals. You may even have a problem using normal switches because they are not made for high speed signals either.
    The best bet would be to look for something that is made for high speed switching, and keep the wiring as short as possible.

    This is also an issue with USB. If the wires are too long it wont work right, or works intermittently.

    I like to switch both power and data lines because this way if anything goes wrong with the computer itself the drive is completely protected. If the data lines are still connected it could get damaged. If you are willing to take this risk however then you have an easier design because you probably only have to switch the power off (USB can handle this, but i dont do that i switch data and + power, leaving only ground connected to the drive). So leaving ground connected is probably ok as long as the other lines are switched, unless you dont mind the extra risk of keeping the data lines connected, and assuming that works with SATA too.

    I would be interested in seeing what you come up with too as i may want to do this also. For the USB i used a mini switch, but kept the wiring very very short by using a USB hub and wiring to the hub rather than using a wire to the port on the computer. So no wire was more than maybe 2 inches long. This was for a USB 2.0 hub, as i havent tried it with a USB 3.0 hub yet.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    High speed switching isn't needed for something built for hot swapping.
     
  10. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    Have now made this sketch, with not switching datalines, just power lines,
    Maybe i will need to wire the switch different, so i will have a OFF-ON-OFF-ON-OFF, that way only one drive at a time gets power.
     
  11. MrAl

    Well-Known Member

    Jun 17, 2014
    2,433
    490
    Hi,

    I dont think any of this is about high speed switching. What it is about is line termination impedance and line impedance. If either isnt right the USB or SATA may have a very difficult time communicating with the device. I found however that if the wires are short the driver is more forgiving even with switches in line with the signal. Remember each switch is a termination to a transmission line and must be respected as such. It may even be necessary to install series resistances to reduce higher voltage ringing or parallel resistance to help correct for the non matching termination impedance.
     
  12. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    Droped the project for now.
     
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