Switch Question

[Mark Jerde]

I haven't done any electronics in years so please excuse the simple
question. Google made me confused.

A device has two three-wire ribbon cables. I want to put an On-Off-On
two-position switch on the cables that functions like this:
1) The same circuit as the uncut cables

AAA --- AAA
BBB --- BBB

2) The cables are "swapped"

AAA --- BBB
BBB --- AAA

Is this a 2P3T switch?

The application is switching a Logitech trackball between right-hand and
left-hand buttons by a switch on the trackball. I write software for a
living and want to have a right-hand trackball on the right side of my
keyboard and a left-hand trackball on the left. I've given up trying to do
it in software so "physicaly swapping" the buttons is the easiest solution I
know of. I could easily cut-and-solder but would prefer a switch for
flexibility.

The manufacturer's page:
http://www.logitech.com/index.cfm/mice_pointers/trackballs/devices/156&cl=US,EN

The cover off showing the two (solid wire) three-wire ribbon cables:
http://i33.tinypic.com/au9zj7.jpg

Thanks.

-- Mark

 

[John Popelish]

Mark Jerde wrote:

I haven't done any electronics in years so please excuse the simple
question. Google made me confused.

A device has two three-wire ribbon cables. I want to put an On-Off-On
two-position switch on the cables that functions like this:
1) The same circuit as the uncut cables

AAA --- AAA
BBB --- BBB

2) The cables are "swapped"

AAA --- BBB
BBB --- AAA

Is this a 2P3T switch?

The application is switching a Logitech trackball between right-hand and
left-hand buttons by a switch on the trackball. I write software for a
living and want to have a right-hand trackball on the right side of my
keyboard and a left-hand trackball on the left. I've given up trying to do
it in software so "physicaly swapping" the buttons is the easiest solution I
know of. I could easily cut-and-solder but would prefer a switch for
flexibility.

The manufacturer's page:
http://www.logitech.com/index.cfm/mice_pointers/trackballs/devices/156&cl=US,EN

The cover off showing the two (solid wire) three-wire ribbon cables:
http://i33.tinypic.com/au9zj7.jpg

A switch pole is a circuit. A throw is a switch position.
So if you want to swap between 2 pairs of 3 circuits you
need a 3 pole double throw switch. But you don't want ot
swap between two pairs of 3 circuits for one 3 circuit
output, you want to reverse connect 3 circuits. This can
certainly be done with a 6 pole double throw switch. The A1
output (the contact that swings between two other
connections) will swing between the A1 and B1 input. The A2
output swings between A2 and B2 inputs, etc., all the way to
the B3 output that swings between the B3 and A3 inputs.


However, in your case, I am willing to bet that one of the A
conductors is directly connected to one of the B conductors.
If you check with an ohm meter, I think you will find a
common wire in both of the 3 conductor cables. For
instance, if, say A1 is always connected to B1, then they
are interchangeable and need not be switched. So you may
need only a 4 pole double throw switch to reverse the
remaining 2 pairs of circuits.

--
Regards,

John Popelish

 

[DJ Delorie]

First off, you probably only need to swap two of those three lines, I
bet one of them on each side is Vdd or Gnd.

Second, the switch you want is a DPDT or 3PDT "on-off-on" switch. The
middle "off" doesn't count as a "throw".

Third, why do you need the center "off" position?

Fourth... buy two, swap the cables in one, and plug them both in.
They're USB, you can do that.

 

[Mark Jerde]

"John Popelish" <jpopelish@rica.net> wrote in message
news:74ednUMoR88mlm3VnZ2dnUVZ_u-dnZ2d@comcast.com...

A switch pole is a circuit. A throw is a switch position. So if you want
to swap between 2 pairs of 3 circuits you need a 3 pole double throw
switch. But you don't want ot swap between two pairs of 3 circuits for
one 3 circuit output, you want to reverse connect 3 circuits. This can
certainly be done with a 6 pole double throw switch. The A1 output (the
contact that swings between two other connections) will swing between the
A1 and B1 input. The A2 output swings between A2 and B2 inputs, etc., all
the way to the B3 output that swings between the B3 and A3 inputs.

Thanks for the clear explaination.

However, in your case, I am willing to bet that one of the A conductors is
directly connected to one of the B conductors. If you check with an ohm
meter, I think you will find a common wire in both of the 3 conductor
cables. For instance, if, say A1 is always connected to B1, then they are
interchangeable and need not be switched. So you may need only a 4 pole
double throw switch to reverse the remaining 2 pairs of circuits.

Good point, by inspection it appears the middle wire in each cable is
ground. I hope the batteries in my mm haven't leaked... ;-)

-- Mark

 

[DJ Delorie]

DJ Delorie <dj@delorie.com> writes:

Second, the switch you want is a DPDT or 3PDT "on-off-on" switch.

John's right, 4PDT or 6PDT, double what I said.

 

[Mark Jerde]

"DJ Delorie" <dj@delorie.com> wrote in message
news:xn8wsvkgmn.fsf@delorie.com...

First off, you probably only need to swap two of those three lines, I
bet one of them on each side is Vdd or Gnd.

Good point.

Second, the switch you want is a DPDT or 3PDT "on-off-on" switch. The
middle "off" doesn't count as a "throw".

Per John's reply reverse-connecting 2 or 3 circuits require 4PDT or 6PDT,
right?

Third, why do you need the center "off" position?

It's not needed. The term "On-Off-On" came from a googled page, describing
"break before make" two position switches. I can't see it would make any
difference in this application.

Fourth... buy two, swap the cables in one, and plug them both in.
They're USB, you can do that.

Swapping cables on a few is no problem, I have at least a dozen. (My
previous-favorite mouse was discountinued so I bought a lifetime supply of
this model.) The switch is mostly for tinkering, and maybe getting back
into electronics again. My oscilloscope has been in its box since 1989. My
daughter is now grown and moved out, so I'm thinking of putting up a bench
in her old room. ;-)

-- Mark

 

[John Popelish]

Mark Jerde wrote:

"DJ Delorie" <dj@delorie.com> wrote:
(snip)
Third, why do you need the center "off" position?

It's not needed. The term "On-Off-On" came from a googled page, describing
"break before make" two position switches. I can't see it would make any
difference in this application.
(snip)

When buying switches, they are described as either on-off-on
or on-on. The first has 3 distinct positions, the middle
one being a stable switch position that disconnects the
poles from both choices. The On-on types come in
make-before-break and break-before-make, but do not have a
stable middle position.

Here is an example of a 4 pole double throw miniature toggle
switch that might work for you.

http://search.digikey.com/scripts/DkSearch/dksus.dll?PName?Name=360-1873-ND

Sorry about the price.

--
Regards,

John Popelish

 

[John Fields]

On Sat, 11 Oct 2008 03:31:14 GMT, "Mark Jerde" <MarkJerde@nospam.nospam>
wrote:

"DJ Delorie" <dj@delorie.com> wrote in message
news:xn8wsvkgmn.fsf@delorie.com...

First off, you probably only need to swap two of those three lines, I
bet one of them on each side is Vdd or Gnd.

Good point.

Second, the switch you want is a DPDT or 3PDT "on-off-on" switch. The
middle "off" doesn't count as a "throw".

Per John's reply reverse-connecting 2 or 3 circuits require 4PDT or 6PDT,
right?


Third, why do you need the center "off" position?

It's not needed. The term "On-Off-On" came from a googled page, describing
"break before make" two position switches. I can't see it would make any
difference in this application.

---
It might make a difference if there was a center OFF position, since
both cables (except for the common ground) would be left floating with
the switch in the center position.

The information you got from the page you Googled was wrong, if you're
talking about a toggle switch, in that a double throw switch with no
center OFF position is called "ON-NONE-ON" and, depending on whether
it's make-before-break or break-before-make, form "D" for the former and
form "C" for the latter.

In your case, if what you're looking for is a toggle switch, it'll be a
4 pole, 2 throw, form "C", ON-NONE-ON switch, and it needs to be wired
like this:



PCBA1 PCBB1
| |
O-->\ <--O
\
O
|
CABLEA1


PCBA3 PCBB3
| |
O-->\ <--O
\
O
|
CABLEA3

PCBB1 PCBA1
| |
O-->\ <--O
\
O
|
CABLEB1


PCBB3 PCBA3
| |
O-->\ <--O
\
O
|
CABLEB3

Most toggles are outrageously expensive anymore, so you might want to go
with a slide switch instead.

Something like:

http://octopart.com/contacts+type--4PDT/manufacturer--E-Switch/search?q=subminiature

JF