Switch debouncing

[Abstract Dissonance]

For one of my projects I decided to use a momentary switch(where its held on
as long as you push it in and when you release it will disconnect... I think
its called momentary switch). The switch basically selects presets and I
will have a couple of them. The idea is like the buttons on a blender where
you press one and it mechanically turns off all the others. I'm trying to do
the same thing digitally. i.e., if I press button A it will turn off all the
others(only one will be on ofcourse). I do this by basicaly using toggle
FF's.

The main issue I have, I think, is the switch debouncing part of it. I've
look on some web sites and they basicaly give a few methods such as a simple
filter circuit(which I think won't work on mine because of the switch type)
and an monostable vibrator. Anways, I feel that I can do this with just some
resistors and capactiors. By looking at the idea for a monoastable vibrator
where they used a capacitor to "slow the change" I figure I can sorta do the
same.


Basicaly the way I see it is that when the switch bounces it will discharge
a capacitor... the more bouncing the more discharge. By setting the
capacitor to slowly charge but discharge quickly when the switch is pressed
the voltage across the capacitor is 0... any bouncing will discharge the
capacitor as it slowly charges. By using a schmitt trigger then I can get a
high only after the capacitor has charged enough. By setting the time
constant one should be able to get rid of the bouncing(its effect is to
length the time it takes to charge).

The circuit is

---- Schmitt Trigger - Out
|
V --- R1 --+-- Switch --- R2 --- GND
|
--- C1 -- GND



What I'm wondering is if this is an effective circuit(i.e., if its
practical). I can simulate it and it seems like it would work but I have no
idea if it will work in the real world(and I have no components to test it
but will order some soon after I get a general idea what I need).

I figure the only problem is that if the person pushing the button pushes it
to fast then it will increase the time the button is "activated" and it
won't change anything... not sure if one could get the time constant down
enough so that the bouncing is fixed but not part of the button pressing of
the user.

Heres a link to the a pic:

http://www.geocities.com/abstract_dissonance/SDBC1.JPG

the green is ofcourse the charge on the capacitor(well, voltage) and the red
is my "output". Whenever I hit the switch the capacitor discharges(drop on
the green line) rather quickly and tries to "recover". Each suscessful time
I hit the switch I try to hit it several more times a row to simulate the
bouncing. Note at the last time there are two red "boxes" next to each other
which would be problem I think... I think this can be fixed with setting the
appropriate resistor and capacitor values though.


Any ideas?

Thanks,
AD

 

[Richard H.]

The main issue I have, I think, is the switch debouncing part of it. I've
look on some web sites and they basicaly give a few methods such as a simple
filter circuit(which I think won't work on mine because of the switch type)
and an monostable vibrator. Anways, I feel that I can do this with just some
resistors and capactiors. By looking at the idea for a monoastable vibrator
where they used a capacitor to "slow the change" I figure I can sorta do the
same.

http://www.ganssle.com/debouncing.htm

It's got a good bit of research on the problem, and ways to solve it
with various hardware and software solutions.

Cheers,
Richard

 

[Ben Bradley]

For one of my projects I decided to use a momentary switch(where its held on
as long as you push it in and when you release it will disconnect... I think
its called momentary switch). The switch basically selects presets and I
will have a couple of them. The idea is like the buttons on a blender where
you press one and it mechanically turns off all the others. I'm trying to do
the same thing digitally. i.e., if I press button A it will turn off all the
others(only one will be on ofcourse). I do this by basicaly using toggle
FF's.

The main issue I have, I think, is the switch debouncing part of it. I've

Ironically, in this application, a bouncing switch won't do
anything different than a perfectly operating switch (once a button
'selects' a FF, 'selecting' it again won't change anything).

look on some web sites and they basicaly give a few methods such as a simple
filter circuit(which I think won't work on mine because of the switch type)
and an monostable vibrator. Anways, I feel that I can do this with just some
resistors and capactiors. By looking at the idea for a monoastable vibrator
where they used a capacitor to "slow the change" I figure I can sorta do the
same.


Basicaly the way I see it is that when the switch bounces it will discharge
a capacitor... the more bouncing the more discharge. By setting the
capacitor to slowly charge but discharge quickly when the switch is pressed
the voltage across the capacitor is 0... any bouncing will discharge the
capacitor as it slowly charges. By using a schmitt trigger then I can get a
high only after the capacitor has charged enough. By setting the time
constant one should be able to get rid of the bouncing(its effect is to
length the time it takes to charge).

The circuit is

---- Schmitt Trigger - Out
|
V --- R1 --+-- Switch --- R2 --- GND
|
--- C1 -- GND



What I'm wondering is if this is an effective circuit(i.e., if its
practical). I can simulate it and it seems like it would work but I have no
idea if it will work in the real world(and I have no components to test it
but will order some soon after I get a general idea what I need).

I figure the only problem is that if the person pushing the button pushes it
to fast then it will increase the time the button is "activated" and it
won't change anything... not sure if one could get the time constant down
enough so that the bouncing is fixed but not part of the button pressing of
the user.

Heres a link to the a pic:

http://www.geocities.com/abstract_dissonance/SDBC1.JPG

the green is ofcourse the charge on the capacitor(well, voltage) and the red
is my "output". Whenever I hit the switch the capacitor discharges(drop on
the green line) rather quickly and tries to "recover". Each suscessful time
I hit the switch I try to hit it several more times a row to simulate the
bouncing. Note at the last time there are two red "boxes" next to each other
which would be problem I think... I think this can be fixed with setting the
appropriate resistor and capacitor values though.


Any ideas?

Long lecture short, you're on the right track.

 

[Abstract Dissonance]

Ironically, in this application, a bouncing switch won't do
anything different than a perfectly operating switch (once a button
'selects' a FF, 'selecting' it again won't change anything).

?

I'm toggling though. If the switch bounces an odd number of times I'll end
up toggling it to the same state it was(hence no toggle) ;/ right?

i.e.

In - Toggle FF - Out

if In = 1 then Out = 0, if In = 0 then Out = 1... i.e. basicaly an inverter
except it holds the state... so consecutive presses of the button will
toggle the original state... but since the switch will bounce those
consecutive presses could be from the bounce and there might be a random
number of them.

Long lecture short, you're on the right track.

I hope so

 

[Abstract Dissonance]

http://www.ganssle.com/debouncing.htm

It's got a good bit of research on the problem, and ways to solve it with
various hardware and software solutions.

Cool. While from glancing over it I don't think it deals with momentary
switches I might be able to adapt one of the methods.

Cheers,
Richard

Thanks,
AD

 

[Ben Bradley]

?

I'm toggling though. If the switch bounces an odd number of times I'll end
up toggling it to the same state it was(hence no toggle) ;/ right?

i.e.

In - Toggle FF - Out

if In = 1 then Out = 0, if In = 0 then Out = 1... i.e. basicaly an inverter
except it holds the state... so consecutive presses of the button will
toggle the original state... but since the switch will bounce those
consecutive presses could be from the bounce and there might be a random
number of them.

So this thing only has two states? I was thinking of the blender
mechanism with eight or so buttons. To do it with digital logic, each
button would go to the set input of its FF, and the reset inputs of
all the others (through diodes or OR gates), thus pressing a button
will ALLWAYS set its respective FF and clear the others.

 

[Abstract Dissonance]

So this thing only has two states? I was thinking of the blender
mechanism with eight or so buttons. To do it with digital logic, each
button would go to the set input of its FF, and the reset inputs of
all the others (through diodes or OR gates), thus pressing a button
will ALLWAYS set its respective FF and clear the others.

yes, but its cause the button itself is not a switch but a momentary button.
So the button is always off except for a few impulses.. this will cause the
state to toggle "randomly". This is similar to a standard switch but the
standard switch always toggles its state after the bounces(so after a little
time the switch will be in the opposite state... for the momentary switch it
always ends up in its same state after a little time).

using your method also will not physically "push" out the button like it
does on a blender. Hence if I used blender like switches there would be an
"in" state and an "out" state... something I want to avoid.. I just want an
out state basicaly... but when pushed in it "momentarily" shorts across the
switch(but doesn't hold it else I gotta figure some way to "undo" it when
other switches are pressed(like the blender does)).

So the problem is more serious than a "latching" type of switch since you
have to digitally latch it.

Maybe this is the way to describe it: say you have a telephone pad. You want
it so that the puttons are momentary... i.e., when you push them it makes
contact only for a very short period of time(a few ns or so guess?) but the
tone produced lasts until another button is pushed... each button
corresponds to some different tone but you don't want to hear multiple tones
simulataneously.


i.e., I'm kinda converting a momentary switch into a SPST digitally. I
can't use a SPST because of the design I want but I need the momentary
switch to act like one. With an normal SPST switch, like I said before, the
state will end up, if 0, a 1 after the bounces... so even if you don't worry
about the bounces then you will still get a toggle...

for the momentary switch though... when you push it, it will go from 0 to 1
for a few ns then back to 0. Hence you can make it into an SPST with a
toggle... but then cause real switches bounce it causes a toggle with each
bounce.

There might be a better way to do this though... its just the method I came
up with when trying to do my project.

The reason why you can't use some switch that stays in its state when
switched is cause somehow you have to mechanically switch the switches state
when another button is pressed. The blenders do this mechanically with a
lever I guess but I don't think there is a way to do it
electronically(except maybe some type of relay like switch). My idea is to
allow the buttons to only go into a "set" state mechanically for an instant
but to keep track of them digitally.

I could do this in software with an MCU probably much easier by just hooking
up each button to an in pin and then detecting when one is changed and just
remember it... ignore the bounces and then listen again and on a set just
toggle the value stored.


heh, to be a little more clear suppose this circuit is simulated

VCC --- Momentary Switch --- Toggle Flip flop --- resistor --- GND

the Switch is such that when you press space bar the switch is made contact
with and a short results across it only for an instant. (i.e., its a
momentary switch that you can control by hitting your space bar). Now each
time you hit the space bar the output at Out is inverted

now in reality there will be a mechanical bounce that occurs randomly... it
would be like hitting the space bar several times in a row... each hit will
toggle the output... after n hits the state will be 0, say, if n is even and
1 if n is odd.

you can also think of the momentary switch simply as a SPST switch which is
used in such a way that one turns it on then off really quick... never
letting it stay switched on for more than a few ns. (ofcourse this requires
pressing the button twice to do this while for the momentary switch it is
only once). Now the SPST basicaly almost always is in the off position
except for "spikes". These spikes can't control the T on a normal flip flop
cause immedately when you set T you reset it so its always 0.



I don't know... maybe that makes some sense ;/

Thanks,
AD

 

[[email protected]]

yes, but its cause the button itself is not a switch but a momentary button.
So the button is always off except for a few impulses.. this will cause the
state to toggle "randomly". This is similar to a standard switch but the
standard switch always toggles its state after the bounces(so after a little
time the switch will be in the opposite state... for the momentary switch it
always ends up in its same state after a little time).

using your method also will not physically "push" out the button like it
does on a blender. Hence if I used blender like switches there would be an
"in" state and an "out" state... something I want to avoid.. I just want an
out state basicaly... but when pushed in it "momentarily" shorts across the
switch(but doesn't hold it else I gotta figure some way to "undo" it when
other switches are pressed(like the blender does)).

So the problem is more serious than a "latching" type of switch since you
have to digitally latch it.

Maybe this is the way to describe it: say you have a telephone pad. You want
it so that the puttons are momentary... i.e., when you push them it makes
contact only for a very short period of time(a few ns or so guess?) but the
tone produced lasts until another button is pushed... each button
corresponds to some different tone but you don't want to hear multiple tones
simulataneously.


i.e., I'm kinda converting a momentary switch into a SPST digitally. I
can't use a SPST because of the design I want but I need the momentary
switch to act like one. With an normal SPST switch, like I said before, the
state will end up, if 0, a 1 after the bounces... so even if you don't worry
about the bounces then you will still get a toggle...

for the momentary switch though... when you push it, it will go from 0 to 1
for a few ns then back to 0. Hence you can make it into an SPST with a
toggle... but then cause real switches bounce it causes a toggle with each
bounce.

There might be a better way to do this though... its just the method I came
up with when trying to do my project.

The reason why you can't use some switch that stays in its state when
switched is cause somehow you have to mechanically switch the switches state
when another button is pressed. The blenders do this mechanically with a
lever I guess but I don't think there is a way to do it
electronically(except maybe some type of relay like switch). My idea is to
allow the buttons to only go into a "set" state mechanically for an instant
but to keep track of them digitally.

I could do this in software with an MCU probably much easier by just hooking
up each button to an in pin and then detecting when one is changed and just
remember it... ignore the bounces and then listen again and on a set just
toggle the value stored.


heh, to be a little more clear suppose this circuit is simulated

VCC --- Momentary Switch --- Toggle Flip flop --- resistor --- GND

the Switch is such that when you press space bar the switch is made contact
with and a short results across it only for an instant. (i.e., its a
momentary switch that you can control by hitting your space bar). Now each
time you hit the space bar the output at Out is inverted

now in reality there will be a mechanical bounce that occurs randomly... it
would be like hitting the space bar several times in a row... each hit will
toggle the output... after n hits the state will be 0, say, if n is even and
1 if n is odd.

you can also think of the momentary switch simply as a SPST switch which is
used in such a way that one turns it on then off really quick... never
letting it stay switched on for more than a few ns. (ofcourse this requires
pressing the button twice to do this while for the momentary switch it is
only once). Now the SPST basicaly almost always is in the off position
except for "spikes". These spikes can't control the T on a normal flip flop
cause immedately when you set T you reset it so its always 0.



I don't know... maybe that makes some sense ;/

Thanks,
AD

Ben was suggesting this set-up:

buttons: A, B, C, reset

setA = A
resetA = B+C+reset
setB = B
resetB = A+C+reset
setC = C
reset C = A+B+reset

This uses s-r bistables (set/resetA, set/resetB...). The ON buttons
simply sets its own bistable as well as resets all other bistables. An
extra reset button simply resets all bistables. This requires a lot of
OR gates. Of course, you can diodes and pull-ups to implement wired-OR.

In this set-up, there is no toggling. So you don't have to really worry
about debouncing.

 

[Abstract Dissonance]

Ben was suggesting this set-up:

buttons: A, B, C, reset

setA = A
resetA = B+C+reset
setB = B
resetB = A+C+reset
setC = C
reset C = A+B+reset

This uses s-r bistables (set/resetA, set/resetB...). The ON buttons
simply sets its own bistable as well as resets all other bistables. An
extra reset button simply resets all bistables. This requires a lot of
OR gates. Of course, you can diodes and pull-ups to implement wired-OR.

In this set-up, there is no toggling. So you don't have to really worry
about debouncing.

well, I don't really like the idea of the reset button. It requires the user
to press two buttons for just one. There are two reasons for this, one I
feel it is inconvienent and not very pratical for the application(the
switching has to be seemless not non instrusive as much as possible) and
there is limited room. I at most can have 4 buttons(or so, it depends) if
that. Each buttons represents a present and I'd rather have 4 presents than
3 and a reset. This is the reason for the specific use of the momentary
switch and having to "toggle" and stuff instead of just using a couple of
SPST switches.


AD

 

[Deefoo]

well, I don't really like the idea of the reset button. It requires the user
to press two buttons for just one. There are two reasons for this, one I
feel it is inconvienent and not very pratical for the application(the
switching has to be seemless not non instrusive as much as possible) and
there is limited room. I at most can have 4 buttons(or so, it depends) if
that. Each buttons represents a present and I'd rather have 4 presents than
3 and a reset. This is the reason for the specific use of the momentary
switch and having to "toggle" and stuff instead of just using a couple of
SPST switches.


AD

You're not getting Ben's idea. There is no reset button and there are no
SPST switches in his setup. Each momentary switch will genereate a pulse
when you press and then release it. This pulse is used to set its
corresponding flip-flop and to reset the others. Lets assume flip-flops with
active low set and reset inputs like the 7474. Each switch is connected to
the 0V on one side and the other side to the (pre)set input of its own
flip-flop and, through diodes (anode to reset), to the reset (clear) lines
of all other flip-flops. Note that you will need pull-up resistors (to +5V)
on the set and reset inputs of all flip-flops so that these inputs are in a
known (inactive) state when no switches are being pressed. Bouncing is now
no longer an issue because it are just more pulses that cannot change the
state of the flip-flops once they are set by the first bounce/pulse. Still
assuming a 7474, you should also tie all the D and CLK lines (all unused
inputs) to a power line like 0V.

If my count is correct, for 4 switches you will need 2 7474, 8 resistors
(10k) and 12 diodes (1N4148 or something like that).

--DF

 

[GrandPaBobby]

You might consider this approach in which contact bounce is irrelevant:

Use the temporary closure of the momentary switch contact to activate a
latching relay. This relay could be in any form -- mechanical,
solid-state. The output (or contact closure) does whatever you want.
Multiple switch activations (or contact bounce) will have no effect as
the relay is already locked. This circuit would be replicated for each
"blender speed" desired.

Concurrently, the output of the momentary switch is fed to the reset
function of all other latching relays. This latches them in the "off"
mode and again, multiple pushes of the button or any contact bounce is
irrelevant as the first pulse has locked the relay in the off mode.

To test this, I spent 5 minutes and wrote a small program in ladder
logic for a Zelio smart relay. It works as stated. Hope this helps.

Robert
========================================================

 

[Abstract Dissonance]

You're not getting Ben's idea. There is no reset button and there are no
SPST switches in his setup. Each momentary switch will genereate a pulse
when you press and then release it. This pulse is used to set its
corresponding flip-flop and to reset the others. Lets assume flip-flops
with
active low set and reset inputs like the 7474. Each switch is connected to
the 0V on one side and the other side to the (pre)set input of its own
flip-flop and, through diodes (anode to reset), to the reset (clear) lines
of all other flip-flops. Note that you will need pull-up resistors (to
+5V)
on the set and reset inputs of all flip-flops so that these inputs are in
a
known (inactive) state when no switches are being pressed. Bouncing is now
no longer an issue because it are just more pulses that cannot change the
state of the flip-flops once they are set by the first bounce/pulse. Still
assuming a 7474, you should also tie all the D and CLK lines (all unused
inputs) to a power line like 0V.

If my count is correct, for 4 switches you will need 2 7474, 8 resistors
(10k) and 12 diodes (1N4148 or something like that).

I don't get it ;/ (sorry.. but I just started in EE about a week ago )

oh, I get it now. duh I wasn't think about the other buttons. You guys
are right. Not even sure why I wanted to do the toggling now ;/ Maybe it
had to do with something else or I was just being dense. I was focusing so
much on the single switch but for my application I don't need it. Not sure
if I had something else in mind or if I was just being stupid. Brain is
kinda fried right now... to much work.

Thanks,
AD

 

[Abstract Dissonance]

You might consider this approach in which contact bounce is irrelevant:

Use the temporary closure of the momentary switch contact to activate a
latching relay. This relay could be in any form -- mechanical,
solid-state. The output (or contact closure) does whatever you want.
Multiple switch activations (or contact bounce) will have no effect as
the relay is already locked. This circuit would be replicated for each
"blender speed" desired.

Concurrently, the output of the momentary switch is fed to the reset
function of all other latching relays. This latches them in the "off"
mode and again, multiple pushes of the button or any contact bounce is
irrelevant as the first pulse has locked the relay in the off mode.

To test this, I spent 5 minutes and wrote a small program in ladder
logic for a Zelio smart relay. It works as stated. Hope this helps.

yeah, I think I got it now. Not sure what I was thinking but I got into the
idea about just using one button or something and didn't realize how the
others would make it much easier. (cause in fact I don't want to toggle the
switches

I think I was looking at some small tree and forgot I was in a forest.

Robert
========================================================

<snip>

Thanks,
AD

 

[Jon]

If you can use a SPDT momentary switch, here's an easy way to debounce:
Connect 2 2-input NAND gates in a latch configuration (Output of gate
A to one input of gate B; Output of gate B to one input of Gate A.
Connect the two "fixed" switch terminals to the two remaining gate
inputs. Connect the "swinger" of the switch to ground. This circuit
will de-bounce for an indefinite bounce period. The only restriction
is that the switch "swinger" can not bounce between the other 2
contacts. This should not be a problem. I've never seen a SPDT swith
(or relay) that does this.

 

[Rich Grise]

For one of my projects I decided to use a momentary switch(where its held on
as long as you push it in and when you release it will disconnect... I think
its called momentary switch). The switch basically selects presets and I
will have a couple of them. The idea is like the buttons on a blender where
you press one and it mechanically turns off all the others. I'm trying to do
the same thing digitally. i.e., if I press button A it will turn off all the
others(only one will be on ofcourse). I do this by basicaly using toggle
FF's. ....
The circuit is

---- Schmitt Trigger - Out
|
V --- R1 --+-- Switch --- R2 --- GND
|
--- C1 -- GND

Notwithstanding what Ben Bradley said about an R-S flip-flop if it gets
multiple "sets" or "resets", to answer your debouncer question, lose R2,
and go directly from the switch to ground:

---- Schmitt Trigger - Out
|
V --- R1 --+-- Switch ------ GND
|
--- C1 -- GND

That will immediately discharge the capacitor, and with the Schmitt, it
doesn't matter how long as it takes to charge, as long as it's quicker
than the next time they push the button! ;-)

There are also "Jeopardy buttons"-type circuits on the internet, which
would give you your lockout, but with independent buttons, you might
even not need that much logic - there isn't going to be any competition
between the buttons, so you don't need a priority resolver, just a - OK,
I think I've got it.

Take another capacitor, from the switch/R1/cap/ST junction, about 1 nf,
and on its other side, put a 1K or so resistor to +Vcc. Condition that
with a couple of diodes, (one each to +Vcc and to ground, reverse biased,
of course - this clamps the spike), and send it to the "reset" of _all_
of the flip-flops. It resets them, and then the "set" signal from your
button sets the target flop.

Kewl! I'll try not to dislocate my elbow patting myself on the back.

Cheers!
Rich

 

[Rich Grise]

yes, but its cause the button itself is not a switch but a momentary button.
So the button is always off except for a few impulses.. this will cause the
state to toggle "randomly". This is similar to a standard switch but the
standard switch always toggles its state after the bounces(so after a little
time the switch will be in the opposite state... for the momentary switch it
always ends up in its same state after a little time).

Are you saying that you have "switches" that, when you press them, you
don't know what the state of the switch will be after it gets done
bouncing? Even while your finger is still holding it down? ?:-/

If so, then you need to find a real switch.

Good Luck!
Rich

 

[Rich Grise]

If my count is correct, for 4 switches you will need 2 7474, 8 resistors
(10k) and 12 diodes (1N4148 or something like that).

Why do you need 12 diodes? Can't you just make a negative OR with 4 of
them, and feed all of the resets?

Of course not.

But, if you differentiated it, you could. Just make the negative-going
edge a spike by capacitating it, and they'll all clear, and the one with
the button down will set when the capacitator charges and it comes out
of its indeterminate state. ;-)

Cheers!
Rich

 

[[email protected]]

I don't get it ;/ (sorry.. but I just started in EE about a week ago )

oh, I get it now. duh I wasn't think about the other buttons. You guys
are right. Not even sure why I wanted to do the toggling now ;/ Maybe it
had to do with something else or I was just being dense. I was focusing so
much on the single switch but for my application I don't need it. Not sure
if I had something else in mind or if I was just being stupid. Brain is
kinda fried right now... to much work.

Good that you finally understand it (I used + for OR by the way,
probably should have used the c-like | symbol instead).

I still think you need that reset button. Consider the blender again.
There must be a button to turn it OFF instead of just changing speed.
Unless of course that is not important in your application. Don't you
usually find something like:

[ 1 ] [ 2 ] [ 3 ] [OFF]

 

[Abstract Dissonance]

I don't get it ;/ (sorry.. but I just started in EE about a week ago )

oh, I get it now. duh I wasn't think about the other buttons. You
guys
are right. Not even sure why I wanted to do the toggling now ;/ Maybe it
had to do with something else or I was just being dense. I was focusing
so
much on the single switch but for my application I don't need it. Not
sure
if I had something else in mind or if I was just being stupid. Brain is
kinda fried right now... to much work.

Good that you finally understand it (I used + for OR by the way,
probably should have used the c-like | symbol instead).

I still think you need that reset button. Consider the blender again.
There must be a button to turn it OFF instead of just changing speed.
Unless of course that is not important in your application. Don't you
usually find something like:

[ 1 ] [ 2 ] [ 3 ] [OFF]

Well, the problem was that I was originally going to have it so n buttons
acted like a group. You would make a button combination to select a preset.
So with n buttons one would have 2^n potential combinations... then I
figured that it might just be to much trouble to do that and much easier
just to have one button per preset but got hung up on the debouncing stuff.
Its still something I want to look into though since its been pretty
interesting.

Thanks for the help though.
AD

 

[Abstract Dissonance]

If you can use a SPDT momentary switch, here's an easy way to debounce:
Connect 2 2-input NAND gates in a latch configuration (Output of gate
A to one input of gate B; Output of gate B to one input of Gate A.
Connect the two "fixed" switch terminals to the two remaining gate
inputs. Connect the "swinger" of the switch to ground. This circuit
will de-bounce for an indefinite bounce period. The only restriction
is that the switch "swinger" can not bounce between the other 2
contacts. This should not be a problem. I've never seen a SPDT swith
(or relay) that does this.

Ok, I'll keep that in mind. I'm not to familiary with all the different
types of switches and stuff and not sure which is the best method. I
actually might end up switching to a rotary style switch so I can save some
space but get more poles(?).

Thanks,
AD