Mouse project (the computer kind)

I have a bunch of servers connected through an 8-port Omniswitch, but i’m plagued with the typical mouse issues that occur with these switches (after switching inputs, the mouse feed will often get corrupted). The only sure-fire way to solve this is to unplug the mouse and then plug it back in. Needless to say, this gets to be a real PITA after a while.

I decided to wire a switch into the mouse cord to enable me to quickly cycle power to the mouse. One half-assed attempt later, and I find myself on the Dope to solve a few problems.

The first problem is isolating the power leads. This page identifies ground as pin 3 and power as pin 4. Unfortunately, the two mouses I’ve disected have the leads at the end of the connector coated in solid plastic, making it impossible to identify which wires are leading to pins 3 and 4. Two of the wires in the first mouse I cracked open were red and black, so I assumed those were the power leads. I wired these into a switch I had lying around, but it didn’t work. The second mouse I opened up had completely differently-colored wires, so I’m not sure that the wires in the first mouse were power leads at all. The circuit board on the second mouse had a + next to one of the leads, so I’m assuming that’s power.

To be absolutely sure, I plan to chop the mouse cord in half, plug it in, and use a multimeter to test leads until I find the right ones. I fear, however, that I may short out the PS2 connecter on the mobo and damage it. That being said, is there any safe way to determine which lead is which?

The second issue is the switch itself. The page cited above states that input is +5VDC and max 500mAmps. The switch I have is rated for 125VDC at .5A. I assumed that was just the maximum rating, and wouldn’t have any impact on the project, but now I’m not so sure. Do I need a switch that’s rated closer to what it’ll be operating at? If so, where can I get one online?

Your gracious insight is appreciated.

mouses = mice :rolleyes:

Can’t help you with the mouse wires, but the switch you have is more than enough to control mouse power. The 125V indicates the maximum voltage the switch’s body and insulation are rated to handle, and the .5 amps = 500 mA - the maximum current the contacts can handle without burning up.

Actually the ones attached to your computers ARE mouses. The fluffy rodenty kind are mice.

I think you’ll find the correct plural is ‘mouse pointing devices’

According to the American Heritage Dictionary, more than one computer mouse can be mice or mouses. Now that we’re done being anal, maybe someone can help midget.

Hmm…Google results swing both ways, so I guess “computer mice” and “computer mouses” both work. As computer ‘mice’ are named after the furry mice, I think I’ll stick with mice. Mice. Mice. Mice…Mice.

Another note: Both mice have one wire that isn’t sheathed (just metal strands running alongside the other wrapped wires). Could this wire be the ground? It has significantly more strands than the others, so I’d imagine that’s the case.

You seem to know how to open up the mice. You seem to be aware of how to test continuity to id which wire goes where in a cut cord. Why do you want to cut the cord? There’s something I’m missing here. I’d just use an ohmmeter set to test for continuity and test each wire endpoint inside the mice against the pins on the DIN connector. Right?

BTW: I was using Xerox Altos back in the 1970s. The first computers to come “stock” with mice. If you said “mouses” back then you’d get the dirtiest looks. “Mouses” is an affectation.

I would just use a multimeter, but be careful. Attach the meter to the wires, make sure nothing is shorting, then turn the computer on. Take your reading, then turn the computer off before disconnecting the wires. On some computers you can still have 5 volts present at the PS/2 connector even though the computer is “off” so you might need to unplug it rather than just switch it off.

The 5 volts on the motherboard is sometimes protected by a picofuse (looks more like a resistor than a fuse to a novice, if you’re not familiar with picofuses). Sometimes not. Sometimes the 5 volts is basically the output of a 7805 regulator, which is where the 500 milliamp spec comes from. Sometimes the 5 volts is a straight track from the 5 volt power supply, with no regulator, no safety device, no nuthin. Short it, and the track on the motherboard smokes. So be careful.

Your switch should be fine. Just don’t go adding gobs of wire to the line. It’s only a 5 volt line and not meant to be driven any great distance.

I’d probably get a 3 pole switch and turn off the data and clock lines as well. It’s not good practice to drive microcontroller inputs with the microcontroller shut off, though most microcontrollers these days won’t have a problem with it.

Just keep in mind that the PS/2 port connects the microcontroller on the motherboard directly to the microcontroller in the mouse with no buffering or protective circuits of any kind in between. It’s not really designed to be hot swapped, and it’s not terribly forgiving if you muck something up. Keep your switch on the mouse side of the omniswitch, which I know is where you plan on using it, but keep it there even while testing. Keyboard/mouse switches are generally much more forgiving than motherboards.

Just in case you’re open to alternative approaches – have you considered just running all the servers from one workstation using Timbuktu or VNC? Never have a mouse problem that way :slight_smile:

We have most of our servers running on VNC, but we also have a Novell server that gets really touchy with rconsole. Plus, there are times when the network is down or whatnot.

Thanks for all your help thus far, guys. I’ll let you know how it works out.


I had forgotten that my long-unused multimeter had a continuity testing function (thanks ftg :wink: ), so I used that to locate the +/- leads. It was actually the leads I thought it was: unshielded = ground and pin with + symbol = power. Wired it up and it’s golden.

The switch is a three-state slider switch (ON-OFF-ON), which is actually really nice because I can just flick the switch from one extremity to the other to cycle power, rather than having to flick it twice (I’m so lazy…)

Thanks guys!