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#3556682 - 04/15/12 06:32 PM Switches, Buttons, Rotary Encodders, dpdt, spst . . . What? I'm so confused, someone help please?  
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Lupus Offline
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Ok. I'm confused about what all the different kinds of switches and buttons do. Toggles, rotary encoders, etc. I've tried doing some searching, but everything I've read seems to assume you know what all these different acronyms mean and what they are used for.

I guess I'm looking for buttons and switches 101 for the newbie simpit builder.

And I do mean the basics. . .so lets try this:

What is a toggle switch with two positions? One up and one down? If it could be more than one kind, how many could it be and what do they do?

What about a toggle switch with three positions? One up, one middle, and one down?

How about a simple push button? How many varieties of this are there?

What about a push button that 'locks' down on one press and when you push it again, 'unlocks'?

How about multiple-position turn dials? You know, the ones that have knobs and 'click' into 3 or 4 different positions?

What is a rotary encoder and in building a simpit what are some of the things that I'd want to use it for?

How would you set up a switch so that an LED came on to let you know it was 'on' and went off to let you know that function was turned 'off'?

Anything or any kind of thing I left out?

Any basic reading you might recommend?

Inline advert (2nd and 3rd post)

#3556723 - 04/15/12 07:57 PM Re: Switches, Buttons, Rotary Encodders, dpdt, spst . . . What? I'm so confused, someone help please? [Re: Lupus]  
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CobaltUK Offline
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SPST = Single pole double throw

DPDT = Double pole double throw

For our purposes the single pole switch is typical.

SPST The lever only moves between 2 positions and is typical of an ON/OFF or ON ON switch (i think)

SPDT The lever moves between 3 positions eg ON OFF ON and would have 3 wire connections

One or both movements from the centre position may be momentary by which i mean the lever will return by itself to the centre position.

Push switches may latch (stay down until repeat press) or be momentary (return to previous position on release)

Rotary encoders will give a precise output based on the angle the shaft is rotated and need electronics to use/display the output.
You might use one of these connected to rotation pivot of a home built throttle for F16 pit.

Connect your led via a resistor to earth and the other end to the the live/on termunal of your switch. If you put diode wrong way round it won't light but does no harm.

Last edited by CobaltUK; 04/15/12 08:10 PM.
#3556769 - 04/15/12 09:42 PM Re: Switches, Buttons, Rotary Encodders, dpdt, spst . . . What? I'm so confused, someone help please? [Re: CobaltUK]  
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- Ice Offline
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Originally Posted By: CobaltUK
SPDT The lever moves between 3 positions eg ON OFF ON and would have 3 wire connections

Are you sure about this one? IIRC, double-throw simply means that there are two circuits that a switch can throw, but does not mean how many states the switches has, ie ON-ON vs ON-OFF-ON. Not sure though so would like to know.

"Momentary" means the switch or button will register a "click," but will return to the "resting state" as soon as you release it. Like a button that you press and let go and it snaps back to place.

That's all I know... lol, am also contemplating building a panel or two so this will make good reading.


- Ice
#3556989 - 04/16/12 06:11 AM Re: Switches, Buttons, Rotary Encodders, dpdt, spst . . . What? I'm so confused, someone help please? [Re: Lupus]  
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CobaltUK Offline
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SPDT
My take is as illustrated above. ie the switch can connect its main (centre) contact to iether of the other 2.

#3556998 - 04/16/12 07:42 AM Re: Switches, Buttons, Rotary Encodders, dpdt, spst . . . What? I'm so confused, someone help please? [Re: Lupus]  
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GrizzlyT Offline
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Let's start with toggle switches. They are the standard switches used.
They come in various types and sizes but all have a lever that you "throw". Standard toggles are two positions. Don't get confused by calling those positions off and on, because that is not always the case.
If it has three positions, it will list it, in the description. They can be ON-ON-ON, where all three positions have a closure. They can be (typically) ON-OFF-ON, where the center is not connected but either direction is. They can also throw momentary positions in there, too. For example, ON-OFF-ON(MOM) is a switch where the center is not connected, one directions stays in the on position, and the other direction is on but snaps back to center (off), after being thrown.

As for the labeling switches use... like DPDT, SPDT, etc. It breaks down to number of poles and number of throws.
The numbers being single (S), double (D), triple (T).
Think of poles as the number of simultaneous switches being thrown. A triple pole switch is like throwing three switches at once.
Think of throws as the number of ON positions, or switch closures. A SPST switch has only one switch and it only has a closure in one of the two positions. Whereas a SPDT switch will have switch closures in both directions.

Still with me? smile

Pushbutton switches also come in various types and sizes but are usually always momentary switches. They do make latching pushbuttons but they are not the standard, so they will be listed as such.

Rotaries come in three basic types. Rotary switches, encoders, and pulse switches.
Rotary switches can have multiple poles but the basic concept for each pole is a center wiper that rotates around and makes x amount of seperate throws. (Although, rotaries don't usually call them throws. They just list them as "positions".)
Rotary switches can also be set up with stops, so that it only turns left or right so many positions. The stops can be removed but the switch closures just repeat themselves, as you rotate around again. So a 5 position rotary, without stops, that is rotated CW will generate the following sequence 1,2,3,4,5,1,2,3,4,5, etc. And CCW will generate 5,4,3,2,1,5,4,3,2,1, etc.

Encoders are a different beast. Unlike other switches, they are not passive. They require special wiring and your controller has to have encoder inputs. They are not interchangeable with a standard rotary. They usually have very light (or no) detent and do not have stops. And unlike passive switches, they are not making repeating closures. Rather, they are sensing the rotational increments and sending out indexing signals to the controller. (i.e. on, off, on, off, on, off, etc.) The cool thing about encoders is that you can set up things like acceleration, where it increments at one rate when turned slowly and another rate when turned rapidly.

Pulse switches are kind of a hybrid of both. They send out momentary switch closures in one direction and seperate closures, in the opposite direction. They are like encoders in that they have no stops but they are like rotary switches in that they are passive switches and require no special wiring or controller inputs.

To review....
- Toggle switches are the standard off/on switches. This includes rocker switches. Which are just toggles with paddles instead of levers.
You flip a switch and something turns on and stays on until you switch it off. (e.g. Generator ON / Generator OFF)
- Pushbuttons are your momentary switches. They are useful for simulating a keyboard or a number pad, or any switch function that doesn't stay latched on. (e.g. Enter key, or reset button.)
- Rotary switches are useful for selector switches. (e.g. Left Tank / Center Tank / Right tank)
- Encoders and pulse switches are useful for incremental dials. (e.g. radio frequency dial, or trim wheel)



Lastly, setting up LEDs to indicate on positions is usually best done by using a seperate pole of the switch. Some controllers switch the grounds and some controllers switch the voltages. So, wiring the LED inline with the switch closure is a bad idea. Run a seperate 5vdc power supply for the LEDs and strap the LED and it's load resistor to it's own pole of the switch. When you throw the switch, one pole sends your switch closure back to the controller and the other pole provides voltage to the LED.


Phweeeew!! Hope that helps. biggrin


Grizzly's Comanche Simulator
"Fear is the mind killer. - Frank Herbert"
#3557074 - 04/16/12 12:46 PM Re: Switches, Buttons, Rotary Encodders, dpdt, spst . . . What? I'm so confused, someone help please? [Re: Lupus]  
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Lupus Offline
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Lupus  Offline
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It does, thank you. And I stayed with you through most of it.

With a Double Pole switch, you throw it in one direction and its like your throwing 2 switches? So for example, you might use this one if you have two computers setup in your pit and want to wire both their power buttons to one switch? So you would use a STDP momentary push-button(although as a push-button it wouldn't be labeled that way since single throw is the standard)?

One more example, if the sim we are flying recognizes individual and separate engine starts, if we wanted to wire both engines to a single button press, we would use a Double Poled switch right?

As for Toggles, in our use as flight simmers, given that the controls of most of our sims are setup to receive input from momentary buttons(keyboards) how would we wire and use toggles that are not momentary?

Now, for Rotary encoders, those are the potentiometers in our joy sticks that are used to measure position etc of the throttle, joy stick, and rudder peddles? And anything else that we would use where the position of the switch is what we want read, like trim wheels, toe brakes, etc.?

Still not clear on Pulse switches? What would I want to use those for?

I also don't understand your explanation of how to wire an LED? Can you please clarify?

Thank you very much for your help.

#3557088 - 04/16/12 01:20 PM Re: Switches, Buttons, Rotary Encodders, dpdt, spst . . . What? I'm so confused, someone help please? [Re: Lupus]  
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AndyB Offline
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Hi Lupus,

I think I can help a bit here.

Rotary encoders aren't potentiometers. Potentiometers are circular pieces of carbon inside a metal can. there is a connection at each end of the carbon "track". there is also a connection to a "wiper" connected to the spindle of the pot. As you rotate the spindle the resistance between the wiper and the end connectings will uncrease/decrease and this change is what is used in joysticks, rudder pedals, etc

There are a few ways to use toggles in a sim.

One way is to use the momentary type as I have in my pit. To start the engine turning I push the toggle forward. This causes a keystroke to be sent to the PC. When I release the toggle, it springs back to the original position. I'm sure you've seen clips/pics of the flip up type covers in fighter pits to fire missles. They can be that type of switch.

Secondly, some interface cards like the Hagstrom will accept normal toggle switches as inputs and only send the keystroke when the switch changes position. i.e Landing gear switch

Thirdly, you can build a small circuit that sends a pulse like a pushbutton switch every time the switch changes position. Have a look at GrizzlyT's site, he has a circuit for this on it.



Pulse switches look like rotary switches. But the spindle is spring loaded to return to one position ( which is off). When you turn the spindle to the left a bit inside shorts two connections. This causes that pair of outputs to be shorted, open, shorted, open etc until you release it (just like multiple key strokes). when released, it return to the centre. If you turn it to the right the bit inside shorts two different connections and "pulses" are produced at the other output.

This is my understanding of how the pulse switch works, but I may be missing bits.


Hope this doesn't confuse you more.....

Andy


Andy's simpit: http://www.simpit.me.uk
#3557097 - 04/16/12 01:36 PM Re: Switches, Buttons, Rotary Encodders, dpdt, spst . . . What? I'm so confused, someone help please? [Re: Lupus]  
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AndyB Offline
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AndyB  Offline
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Ayrshire, Scotland
Hi Again,

Here's some wee pictures that might help you get your head around the basics:



Momentary action toggles would look the same as the ordinary ones but with a spring under the bar.


Cheers,

Andy

Last edited by AndyB; 04/16/12 01:37 PM.

Andy's simpit: http://www.simpit.me.uk
#3557117 - 04/16/12 02:30 PM Re: Switches, Buttons, Rotary Encodders, dpdt, spst . . . What? I'm so confused, someone help please? [Re: Lupus]  
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Sokol1 Offline
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Some tips here:

http://www.fscockpit.com/switches.html

Rotary Switch can be MOMENTARY or CHANGE OVER.

Sokol1

#3557267 - 04/16/12 06:34 PM Re: Switches, Buttons, Rotary Encodders, dpdt, spst . . . What? I'm so confused, someone help please? [Re: Lupus]  
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GrizzlyT Offline
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GrizzlyT  Offline
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Sterling Heights, Michigan
Originally Posted By: Lupus
With a Double Pole switch, you throw it in one direction and its like your throwing 2 switches?

Yes. And you would use a double-pole pushbutton, in your example.


Originally Posted By: Lupus
As for Toggles, in our use as flight simmers, given that the controls of most of our sims are setup to receive input from momentary buttons (keyboards) how would we wire and use toggles that are not momentary?

I wouldn't say that's exactly the case. Yes, the software is setup to use key presses to control it. And PCs want momentary inputs from keyboards. But that doesn't hold true with the multiple choices of controllers you can use to interface your cockpit switches. Some controllers do require momentary switches. Some do not. You need to plan out your cockpit and how detailed it is going to be. You may need to use all of these switch types, if you expect your finished project to look and feel realistic.

Originally Posted By: Lupus
Now, for Rotary encoders, those are the potentiometers in our joy sticks that are used to measure position etc of the throttle, joy stick, and rudder peddles? And anything else that we would use where the position of the switch is what we want read, like trim wheels, toe brakes, etc.?

No. Encoders are not pots. Your joystick, trim wheel, toe brakes would all probably use a pot. It would depend on the software. For example, MSFS allows you to assign trim to an axis. This you would use a pot for. EECH uses keystrokes to adjust trim. This you could use a pulse switch for. An encoder would be used for things like your radio dials, or GPS. (I don't use any in my pit, BTW.)

Originally Posted By: Lupus
Still not clear on Pulse switches? What would I want to use those for?

A pulse switch is a rotary switch that sends out momentary pulses as you rotate it. It has separate switches for CW and CCW rotation.
For example I use one to control my radar scan size. The radar has 5 (I think?) different scanning widths. The sim uses the keypad 8 to increase the width and the keypad 2 to decrease the width. With a pulse switch, I have 8 wired to the CW switch and 2 wired to the CCW switch. When I turn the dial, every detent increments the scan size up or down.
So it would be used on key presses that require multiple presses to increment or cycle through the values.

Originally Posted By: Lupus
I also don't understand your explanation of how to wire an LED? Can you please clarify?

When using a toggle switch, you use one pole of the switch to connect to the controller and send the key press, and one pole to complete the LED's circuit.
I use a separate 5 volt power supply, for all my lamps. I do not run them through the controller switch wiring, or pull power from the USB bus. So, that 2nd pole just sends the 5 volts to the LED...through a load resistor. (You don't want to fry your LED!)


Grizzly's Comanche Simulator
"Fear is the mind killer. - Frank Herbert"

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