Cherry switch with wire

[Half-Saint]

What's the function of the wire? Just another fixing point for the switch so that it's harder to pull out by hand?

[Icarium]

I think so, yes. Since both feet are on one edge of the case they might also bend easily without it. They might also be reusing PCBs. With the wire you could use the same as for switches with diodes and do anti-ghosting in the controller.

[Limmy]

The wire is called jumper.

If a board has switches with jumpers, it wouldn't work without them.

[Half-Saint]

So, I couldn't simply remove the jumper and put a LED in there and wire it up to the proper LED hole i.e. CAPS LOCK?

[off]

That really depends on where, if anywhere, the jumper wire connects to..
If it is an actual jumper, i.e. with the function to jump, then no; you would be interconnecting two different tracks.
If this particular jumper does not connect to actual traces, then yes!

[kint]

pic for ease of understanding:


switch 1:
No connection to any of the traces - see green arrows, therefore a LED would be possible.

Switch 2:
The trace comes from yellow, goes into the jumper wire orange, has direct connection to red, further to violet of Switch 1.
Or, depending on the actuation of the switch 2, to violet of its own switch 2 and then continues to blue of other switches.

There's also Variant 3, which is unmarked but directly above switch 1, where the jumper wire acts as a bridge without connecting to the switche's own soldering points. This is done to keep the traces to a minimum and layout simple. Also no LED possible.

[Icarium]

kint: I'm not sure what you're trying to say, since those wires aren't connected to anything all those connections passing through them are basically no-ops.

I do agree that they can be used as bridges and should be, too. It makes it easy to get the entire matrix in one layer. Though I don't know if extra layers are as expensive as they used to be.

[off]

@ica, I'm not entirely sure what you are trying to say xD

Some keys (#1) are as kint says 'free' to use for leds.
And personally I am very thankful for keyboards staying one (max 2) layers PCB-wise; good luck tracing one with 3+.

[kint]

kint: I'm not sure what you're trying to say, since those wires aren't connected to anything all those connections passing through them are basically no-ops.
I do agree that they can be used as bridges and should be, too. It makes it easy to get the entire matrix in one layer. Though I don't know if extra layers are as expensive as they used to be.

yes and no. See the Matrix as a whole.
The wire of Switch #1 in the pic, with the green arrows has no function, agreed, could be removed or whatever.

The wire of the unmarked switch 3 (the one above 1) has a function. It is a bridge and whilst it has no function for it's own switch #3, its utterly important for switch #1, because it leads the trace coming out of the right edge of the pic, through switch #3's bridge wire to the MX soldering (violet arrow) of Switch #1.

If that wouldn't be there, you would have to find a labyrinth like way through the whole PCB - just for one switch. Add this up to 100 Switches and the whole PCb would be much more crowded and messy.

Bridge in Swicth 2 even splits.

Add all this up - yeah, could be done in different layers, but since the wire is in the switchs design anyhow - why not use it for the (cheaper, easier) layouting ?

[Half-Saint]

So, basically I'd have to make a new bridge, if I removed the wire (jumper) where it connected to something. How hard is it to break a trace?

[off]

Depends, how likely are you to inadvertedly(sp?) cut something else?

Just take anything sharp, knife or screwdriver, and scratch it through the path.. just one stroke should do:
-----|-------

[kint]

I recommend removing 1-2mm width i.e. by scratching with a sharp knife, not simply cutting through. If the gap is to skinny the PCB can flex and reconnect. Could end bad. The bridge would be done best with direct jumper wires from the starting points of the jumper/ bridge wires traces. If you do a lot of switch rerouting, this will end up in a bag of snakes.

[ripster]

So, I couldn't simply remove the jumper and put a LED in there and wire it up to the proper LED hole i.e. CAPS LOCK?

That ain't gonna work son.

Voltage (well current actually) is not sufficient.

[off]

... the capslock led that is already there will lose it's power (or amps get halved depending on how he connects what), I'm betting either way the new in-cap led will light up just fine.

[ripster]

Oh, he meant tapping into CapsLock Vcc, not pulling off the scanning matrix from the controller.

Oh yeah, that should work depending on how it is wired up.

[off]

Indeed, that was an entirely different thread.

[ripster]

Picky, picky.

[Peter]

As I understand it, the jumper eliminates 'dead switches' and makes boards that have them 3-4 KRO instead of 2KRO?

[ripster]

Nope, different issue.

See the OCN Mechanical Keyboard Guide for an explanation of this:
http://www.overclock.net/t/491752/mecha ... st_6026727

It's not a very GOOD explanation mind you.....

[Peter]

No, it doesn't explain at all what the wire-jumper actually does .
It only talks about 2KRO or NKRO, but some boards have 3-4KRO ..
(Ignore the limitations of USB plz )

[kint]

As I understand it, the jumper eliminates 'dead switches' and makes boards that have them 3-4 KRO instead of 2KRO?

The wire ist just integral part of the switch. Then having the jumper in mind the PCB traces are laid.
If anything, the jumper wire eliminates the need for a trace, or several depending on the layout -productionwise.
However theoretically you could say that with jumpers there are more routes to a switch possible, therefore enhancing the possible KRO, as I take it.

[ripster]

Cherry Corp sure is enamored of them. Although when doing some multimeter testing on my Cherry Corp SPOS RIcercar special I found half the jumpers were roads to nowhere.

[Half-Saint]

I think Cherry's engineers were pretty smart/practical. I'll show you what I mean in a the couple of days

[off]

Half-Saint- very interested what you're up to now!
Peter/kint; I concur it should allow for more optimal patterns on an otherwise single layered pcb. Samples (photos of the PCB's backs, with the appropriate designation of 3/4/x KRO) would be great to have around though, preventing reinventing wheels etc. Derp. Thanks soar!

[Soarer]

On-topic...
Yes, a single sided PCB would need jumpers, so this is just a way to make assembly easier.

Off-topic-ish...
A switch matrix is fundamentally 2KRO, or NKRO with the addition of a diode/capacitor/resistor per switch.
Any 3KRO or 4KRO keyboard probably has an NKRO switch matrix and the limit is in the controller - for example I have a G80-1000 that is like this.