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Author Topic: Making a simple KVM?  (Read 1566 times)

m_cheng

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Making a simple KVM?
« on: May 04, 2004, 04:38:18 AM »

I'm looking to make a cheap (less than $10), small switch to mount in my keyboard that acts like a KVM switch. It only needs to switch the keyboard between two machines.

Keeping in mind that there are 5 lines in the PS/2 cable from the keyboard to the box, what would be the best way to go about this project?
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monkey_sass

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Making a simple KVM?
« Reply #1 on: May 04, 2004, 09:57:28 AM »

Just splice two cables together and put a switch where the splice is, since a keyboard is not like a ps/2 mouse port (meaning it has to be plugged in at boot time), it should work just like you are unplugging the keyboard from one computer and plugging it into another.  The switch may be hard to find, but some electronics store is bound to have something you need.  If not, you could always use a molex-type connector and just physically 'switch' the connector whenever you want to actually switch.  Total cost should be even under $5.

You might even be able to get away with only putting a switch on one wire (+5v), which would make the whole thing cost even less.
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BalefireX

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Making a simple KVM?
« Reply #2 on: May 04, 2004, 10:04:13 AM »

looking at this pinout:
http://www.bbdsoft.com/keyboard.html

you could probably just use a SPDT switch for the data and clock, and use the same +5 and Ground for both.
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monkey_sass

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Making a simple KVM?
« Reply #3 on: May 04, 2004, 10:26:08 AM »

Another idea:

A cheap keyboard only costs about $7-8.  Just a thought.
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john_is_war

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Making a simple KVM?
« Reply #4 on: May 04, 2004, 11:36:07 AM »

Quote from: monkey_sass
Another idea:

A cheap keyboard only costs about $7-8.  Just a thought.


It's not always about goods.  Maybe someone doens't have a lot of space, or they have an ergo keyboard they like.  Or to quickly switch between two different comps at a workstation.
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Syberz

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Making a simple KVM?
« Reply #5 on: May 04, 2004, 11:40:04 AM »

buy 2 ps/2 extensions, plug one in each pc and tape the two female ends next to eachother close to your keyboard. Plug the keyboard whichever one you need.
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Skylined

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Making a simple KVM?
« Reply #6 on: May 04, 2004, 01:44:46 PM »

What BalefireX said is right.

+5V, Gnd and Clock can be shared between two keyboards.
Then you have Data that is the signal coming from the keyboard, this is what you really need.
Use a SPDT switch and you're done.

I might be mistaken, but I think the Clock signal is given by the port and not by the keyboard.
But if it comes from the keyboard, just use a DPDT switch and wire Data and Clock cables there.
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m_cheng

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Making a simple KVM?
« Reply #7 on: May 08, 2004, 04:46:13 PM »

Thanks guys, I grabbed a switch out of a broken power supply and mounted it on the back of the keyboard. Switched the data and clock and it works great. I also swapped in some blue LEDs while I was at it.

Thanks for all the help!

BTW, if anyone wants to make their own:

there are 5 lines inside the keyboard: black, red, white, green or brown, and black.

The two black lines are ground, the red is +5V. So just switch the white and other color (i had both green and brown in the two PS/2 cables that I used).
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Skylined

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Making a simple KVM?
« Reply #8 on: May 08, 2004, 05:20:43 PM »

Now that I think, maybe taking off the +5V it's enough, but if it already works, leave it that way. :)
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