USB Switch Improvement

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About: Thank you all for following me. Please vote for my invention here: http://contest.techbriefs.com/2019/entries/medical/9681

At home I use two computers connected together to one monitor, one keyboard and one mouse through KVM switch. On the desk I have also a printer, which I share between both computers. Unfortunately the KVM switch does not support USB multiplexing and each time when I print, I have to reconnect the printer playing with the USB cables. To make my life easier I decided to buy some cheap USB switch. I found this one in Aliexpress. I was interested to check what is inside and I found that it is fully mechanical. That means also that it is bidirectional - can be used for different purposes :

  • The one for which I needed - to connect one printer to two computers
  • To switch between two USB devices connected to one computer. In this case also special USB cables would be required - both sides male to male connector type. This use can allow for example two Arduinos to be connected to the computer and multiplexed fast or two external USB audio cards....etc.

It can be seen on the picture that the commutation between two USB B-type ports is performed by the use simple two positions switch. There is a picture showing which port is active when the switch is pressed and not.

To make the switch a little more convenient to use I decided to mount two LED's showing (for the first use, which of both computers is ON in the moment and which USB device is connected to the computer in the second way of use)

This instructable describes briefly how this can be done.

Step 1: Dissembling and Inspection of the USB Switch

On the bottom of the box can be found two screws. When removed the case can be open. Inspecting the board I saw that the supply and ground wires are also multiplexed - that was what I needed.

Step 2: Parts Needed

  • two LED's - I chose 5mm with different colors - to be able to distinguish them in the dark
  • one 330 Ohm to 1.5 kOhm resistor
  • some insulated wires
  • a piece of thermo-shrinking tube.
  • two LED holders (optional)

Step 3: Mounting of the LED's

I drilled two holes for the diodes on the top of the case. The holes were done in such positions that the mounted LED's are located in the free place between the USB sockets and the switch. I mounted the LED holders and inserted the LED;s there. To fix then strongly I used a hot glue gun.

Step 4: Electrical Connections - Soldering

I connected the LED;s cathodes together.At that joint I soldered the resistor with soldered wire (blue one) on the other terminal. I put the thetmo-shrinking tube over the resistor and heated it. At the LED's anode pins I soldered two red wires. These red wires I have soldered directly to the supply pins of the corresponding USB socket (see the picture where). I inserted the blue (negative) wire through an existing hole of the PCB, layed the board on its right position and soldered the blue wire to the GND pin of the female A-type USB socket. After that I closed the case and fixed it again with the screws.

Step 5: Ready!

I connected the switch to my printer and computers by the use of short USB B type cable. I printed a test page without problems. Everything works fine and I do not need to dig in the cable mix to check which cable where comes from.

And the look is nicer - I like color lights in the twilight, when I sit on my desk usually.

Thank you for reading.

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    7 Discussions

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    blackICE19240

    15 days ago on Step 5

    I bought a coupe of those switches a while ago to change between charging my phone and data transfer to my computer at my desk. They seemed really good at first but I soon realised the current drop through these is ridiculous making charging through them pointless and I also found data transfer very unreliable. Please let me know if you've ever noticed something similar.

    6 replies
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    MilenblackICE19240

    Reply 15 days ago

    Hi,
    Until now I used the switch only to print few pages. I did not have any problems. May be after some time, when the switch contacts oxidise I will have similar problems. In your case may be a USB hub would work better.
    Regards
    Milen

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    blackICE19240Milen

    Reply 14 days ago

    I had this problem when they were new, of course they may have been in storage for a long time but I don't see any rust on the connectors. I expect they just use extremely cheap PCBs which can't carry much current. I've just tried using my mouse with one of them and it works perfectly but the current draw will be tiny and I think that's why. Try charging your phone with it, see if it's not as fast as usual.

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    MilenblackICE19240

    Reply 13 days ago

    Hi,
    I have connected my phone to the usb switch. The phone gave me the message: "Charging slowly with usb. Connect to standard charger to charge faster"

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    blackICE19240Milen

    Reply 13 days ago

    That confirms it. It's really a shame these can't deliver more current, I think they are well designed but I guess they just cheaped out of the thickness of the copper in the PCB - I'm no expert though so this might not be the problem, it seems kinda unlikely.

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    MilenblackICE19240

    Reply 13 days ago

    May be you can try to bridge (parallel) the tracks with thicker wire?

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    blackICE19240Milen

    Reply 12 days ago

    I'd actually considered that but I thought it was waste of time ... but now you've convinced me and I'm going to do it.