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Discussion Starter #1
Hello,

My Alpine INA-W910 only has a single USB Input. I generally leave this hooked upto my iPod, but sometimes my friends will bring a USB Stick or something they want to plug in. The way my system is configured, it is inconvenient to un-plug the iPod USB>30-Pin cable and plug in a USB Stick (this requires removing a glove-box panel in my installation).

Does anyone make (or is it possible to DIY) a very simple "2x1" USB Switch?

I need a way to have the single HOST (the W910) swap between two DEVICES (iPod and USB Sticks, etc) - and NOT a standard USB Hub where both peripherals would be seen at the same time.

A standard USB Hub will not work from what I understand (there's no way to select which USB Device the HU is using).

I see Belkin and Siig offer "Peripheral Sharing" devices that allow a SINGLE USB Device to swap between two HOSTS (PC's), these will NOT work. (opposite of what I need).


I was thinking of DIY'ing by using a simple 2x1 switch with 3-4 contacts would do the trick (probably don't need to switch the ground) - but I'm not that familiar with USB in general. I did find this fairly thorough page on USB Switching and termination - but I'm either looking for a pre-built solution, or a simpler way to do this with a physical switch and some simple wiring (I'm not big into DIY'ing CMOS circuits and crap).

Has anyone done something like this - and what did you use? My plans are to re-wire my Truck's factory USB Port into input #1 of the switch (for USB Sticks and crap), wire my iPod cable into input #2 of the switch, and then manually swap back and forth as needed.

I realize I will need to be cautious and avoid switching while the device is selected to prevent "issues" - that's fine. I searched for "2x1 USB Switch" and nothing came up going back to 2010...

Thanks! :cool:
 

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Discussion Starter #4
That is an option I hadn't considered. I use small 2-pole (DPDT) relays in my DIY Pro-Audio Gear (generally for balanced "true bypass" functions) - I'd likely use a single 2-pole version to simplify things. I'm thinking I'd only really *need* to switch the two differential USB Data lines (can probably leave the +5v and Ground connected to both ports persistently w/o issues).

However - does anyone make a pre-fabbed solution? I'm sure someone else has done this?

Thanks for the reply, The Performer! I'll likely go this route unless a pre-built option is available. Could probably wire straight to the mini DPDT relay, too (no PCB)! :cool:
 

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That is an option I hadn't considered. I use small 2-pole (DPDT) relays in my DIY Pro-Audio Gear (generally for balanced "true bypass" functions) - I'd likely use a single 2-pole version to simplify things. I'm thinking I'd only really *need* to switch the two differential USB Data lines (can probably leave the +5v and Ground connected to both ports persistently w/o issues).

However - does anyone make a pre-fabbed solution? I'm sure someone else has done this?

Thanks for the reply, The Performer! I'll likely go this route unless a pre-built option is available. Could probably wire straight to the mini DPDT relay, too (no PCB)! :cool:
Yep, I dint even think about that. You can 100% leave the 5v+ and ground in parallel and have no issues and use just 2 relays.

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Discussion Starter #6
Since these are DPDT Relays - I believe I can just use one ;)



Anyone see any issues with this???

Thanks! :cool:
 

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The only issue I see would be that your HU would be powering both units... or trying to anyway. The USB standard is 500mA, but some devices pull more juice than that. If your HU isn't rated to provide the current you need to run both devices, you'll create a voltage drop on the 5 volt rail.

If it were me, I'd run a 4pdt relay. You can get one for about five bucks at Mouser. Maybe something like this one?

MY4-DC12(S) Omron Industrial | Mouser

The only other thing that MIGHT be an issue is how quickly the relay switches. If it has a long delay (relatively speaking) then the HU will recognize that one device was "unplugged" and the other one was "plugged in." If it's too quick, then the HU may not see the switch take place and try to access data that isn't there. (Different device, different file structure.) In that case, you would want to run two relays and have a delay on/delay off style circuit for them.

Good luck with your project.
 

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Interesting thread. I haven't been able to find any off-the-shelf solution that does this either. I want two USB-controlled processors to be switched and accessible via one computer and one USB cable. Like you said, two devices, individual non-simultaneous use is not what normal USB hubs are designed to do... Following this thread in case of a solution, or if I find something I will post here.
 

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Discussion Starter #9
Thanks for the input, all! I'm going to try the 4PDT relay (go ahead and switch power/ground, too) - and see if the switch time is an issue (good point, Fast Hot Rod!). I'd bet it will be an issue considering the "Switch Time" will be in the mS range or less IMO.

I'm not that familiar with all of the different relay types - but it seems a 4PCO (4 Pole "Center Open" or "ChangeOver") might also work (The "center off" would allow additional switch time for a clean hot-swap). I'm not sure I understand how these work with regard to the switch/coil. How/when does the "Center Off" come into play? I'm familiar with Double-Throw SWITCHES that have On/Off/On "center open" functions - but how does this work on a 4PCO RELAY with a single coil connection???

If I can't do this with (1) relay under $10-$15 - I'll probably just use a descent 4 Pole / 3-Way rotary switch, and just use the switch's middle position as the "Off" (I actually have a switch that should work in my "Spare Parts" box from my DIY Pro-Audio gear!). I'd keep the switch fairly close to the USB Connections to avoid losses and interference - and wire the USB Cables directly to the switch to also avoid losses (and keep the unshieled portion VERY short - 1/4" or less). (Basically like this , but no PCB or LED's)

FWIW - I also found these - But they are a bit bulky for automotive use IMO:
2 Port Manual USB Data Switch Box, 1B to 2A Type, Slim Design - PI Manufacturing Corp.
USB 2 Way Push Button Switch Box 1 A, 2 B Type Ports

Should be pretty cool once I get it figured out IMO...


Rock on!
 

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Discussion Starter #10
FYI - I have this simple 3PDT w/Center OFF switch on the way.

3PDT CENTER OFF MINIATURE TOGGLE SWITCH: Amazon.com: Industrial & Scientific

I figure the 3rd pole will allow me to switch +5V to avoid any current limitations from my W910, and the "Center Off" position will allow me to control the switch time from USB-A to USB-B (while USB is not selected and playing on the W910, of course).

The switch will be fairly close to the USB Cables (will direct wire/solder the cables to the switch), and I'll only have to expose 1" or less of the USB signal cables w/o shielding. Considering the lower data rates on iPods and USB Sticks, I don't foresee any issues (fingers crossed).

Hope to attack this next weekend - will obviously include some dash/console carnage to get in there (have to run a few more wires down my console anyways)...

Thanks for all of the helpful input! :cool:
 

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Hi Randy. Could you please post an update on this project?

I also would like to set up a USB switch for a head unit, and I surely would benefit from your knowledge. Thanks.
 
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