[simpits-tech] Switchs, Rotary and pot
Marv De Beque
simpits-tech@simpits.org
Mon, 05 Aug 2002 18:31:32 -0400
That is an open question.
The answer is, it depends.
However, you have not qualified the exact application, so it is hard to give
you a good answer.
However, since I am constructing a F-16 cockpit, I can tell you what I plan
to use. I will use a potentiometer for almost all of my applications where
there is a knob. Except....
... the caveat is there are many knobs that use a rotary switch and I will
use a rotary switch where it is required. I think you know what a rotary
switch is, but if not, it is a mechanical switch that rotates to preset
positions.
There are not too many places where an encoder will be applicable in my sim.
I may possibly use them for the ICP panel that sticks in the pilots face.
There are 4 thumb wheels that control contrast, brightness, and other
functions on the HUD. An encoder may be physically easier to mount than a
pot in those instances.
Encoders require more expensive circuitry to operate than a pot. General
rule of thumb is that there should be a good reason for using an encoder
where normally a pot will not do.
I would recommend a pot.
That being said, from the scope of the questions you are asking, I wonder
where you are at in your project and what your project goals are? I ask
because I get a sense that you might be putting the cart before the horse.
What is your goal and what is your plan to get there?
I am sure that you can get all the help you need right here, but it is good
to get the basics first, outline your goals, and then we can help you
execute your plan (or at least help you get a plan together).
Marv
--
> From: "Frank Riedel" <frank@rezultat.dk>
> Reply-To: simpits-tech@simpits.org
> Date: Tue, 6 Aug 2002 00:09:33 +0200
> To: <simpits-tech@simpits.org>
> Subject: Re: [simpits-tech] Switchs, Rotary and pot
>
> Great exampels ;o)
> GOT IT ;o)
> BUT - can i use POT instead of ENCODERS in my pit ???
>
> Frank
>
> ----- Original Message -----
> From: "Marv De Beque" <mdebeque@woh.rr.com>
> To: <simpits-tech@simpits.org>
> Sent: Monday, August 05, 2002 11:57 PM
> Subject: Re: [simpits-tech] Switchs, Rotary and pot
>
>
>> No.
>>
>> A pot (short for potentiometer) is a device that rotates over a given
>> portion of a circle. This is usually about 270 degrees, but there are
>> multi-turn pots that rotate 5, 10, or 20 turns from lock to lock.
>>
>> A pot is nothing more than a resistor that can be changed from zero
>> (usually) to its maximum value. 100,000 Ohms is typical for simulator
> use.
>>
>> A pot, theoretically, has an infinite adjustment between its two extreme
>> values (i.e., 0 to 100,000 Ohms). So, like a faucet (in good working
>> order), you can adjust the flow to any value in between.
>>
>> A rotary encoder is different. It is a device that rotates like a pot,
> but
>> instead of acting like a variable resistor, it sends out a set of pulses
> as
>> the knob turns. It is sort of like putting playing cards on the forks of
> a
>> bicycle and turning the wheel. As each spoke passes, an audible click is
>> heard (a pulse). You can count the pulses and then determine how far the
>> wheel has rotated. You need two two playing cards slightly offset in an
>> angular fashion to tell which direction the wheel is rotating. By looking
>> at which card clicks first you can tell direction of spin.
>>
>> The thing about encoders is that they have a "granularity". Unlike a pot
>> which is infinite, there are finite steps to an encoder. There may be any
>> number of steps you can get from a few to several hundred steps per
>> revolution. You can resolve the rotation only down to the step, but you
> can
>> not tell how much an encoder rotates between step steps (i.e., a half
> step).
>>
>> Most encoders do not remember their positions when power to the system is
>> turned off. So, the system must somehow save the last known position if
> it
>> is to pick up where it left off at power down. A pot has the same
>> resistance whether the system has power or not.
>>
>> A pot almost always has a mechanical stop. Resistance can only go so far.
>> An encoder does not necessarily have a mechanical stop and can be rotated
>> continuously without stopping.
>>
>> An example of an encoder is a computer mouse (at least the old ones).
> Some
>> new car stereos have them too.
>>
>> Two different animals that can be used in similar ways and each has its
>> advantages.
>>
>> Sorry for the long message, but I am short on time.
>>
>> Marv
>> --
>>
>>
>>> From: "Frank Riedel" <frank@rezultat.dk>
>>> Reply-To: simpits-tech@simpits.org
>>> Date: Mon, 5 Aug 2002 23:35:45 +0200
>>> To: <simpits-tech@simpits.org>
>>> Subject: Re: [simpits-tech] Switchs, Rotary and pot
>>>
>>> Thanks alot for the explanation ;o)
>>>
>>> I found the F16 panels at simpits.org...
>>>
>>> Did i get it right - rotary encoders = potentiometers ??
>>>
>>> Thanks
>>> Frank !
>>>
>>> ----- Original Message -----
>>> From: "Andreas Fransson" <andreas.fransson@post.utfors.se>
>>> To: <simpits-tech@simpits.org>
>>> Sent: Monday, August 05, 2002 9:09 PM
>>> Subject: Re: [simpits-tech] Switchs, Rotary and pot
>>>
>>>
>>>> Frank,
>>>>
>>>> 3-way switches are (usually) on-off-on. With or without automatic
> return
>>> to
>>>> center position (not sure what the english expression for this would
> be).
>>>>
>>>> Rotaries, if you mean rotary switches and not rotary encoders, may or
> may
>>>> not have limits. A couple I have here for example do not. They go all
> the
>>>> way around. What they do is just rotate a common ground around a number
> of
>>>> connections. Like a "normal" switch but with many more positions. Mine
>>> have
>>>> 12 I think. You could say that they are "all-on" in the sense that one
>>> lead
>>>> is always active. Encoders are a different breed altogether. They are
>>>> commonly used to sense motion (rotation) rather than indicate switch
>>>> positions.
>>>>
>>>> "Pots", or potentiometers, are basically variable resistors. I you use
> one
>>>> with EPIC, or as a replacement for a joystick pot, it is 100 ohm linear
>>> pots
>>>> you want.
>>>>
>>>> If you use the EPIC, the kind of switches you use are almost
> unimportant.
>>>> EPL (the EPIC programming language) is very flexible. It's not at all
> like
>>>> the standard joystick momentary on/off pushbuttons.
>>>>
>>>> What aircraft (or whatever) panels are you looking for?
>>>>
>>>> Andreas
>>>> http://valhallainc.d2g.com
>>>>
>>>>
>>>> From: "Frank Riedel" <frank@rezultat.dk>
>>>>> Hi All !
>>>>>
>>>>> 3 way switchs - is that off-on-off or ????
>>>>> Rotary - is that 360 dg. or ???
>>>>> 2 way switchs - is that on-on or ???
>>>>> Pot - is that a normal potmeter 100 ohm or ???
>>>>> Is EPIC control all those switchs nomatter if it is on-of or on-on ???
>>>>>
>>>>> Do anyone of you guys have a link to a page where i can read about it
>>> ???
>>>>>
>>>>> and do anyone have a set of drawings of panels without knobs on ????
>>>>>
>>>>> thanks for all your help... i'm on the road for my first real pit ;o)
>>>>>
>>>>> Frank
>>>>
>>>>
>>>>
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>>>
>>>
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>>
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>
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