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Computer vs standard transmitter...

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Old 07-12-2004, 12:33 PM
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Gaffspan
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Default Computer vs standard transmitter...

The other day I had someone recommend a computer transmitter to me to replace my VERY basic skysport 4. Obviously lots of people have computer radio, I was ust wondering what the advantages were (apart from model memory) to justify the extra cost.

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Old 07-12-2004, 03:59 PM
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Lynx
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Default RE: Computer vs standard transmitter...

Expo is a usefull feature, so are multipoint curves, easy ATV/endpoint adjustment, digital trims. There are a hundred features on modern computer transmitters. However if you're just a casual flyer I'd honestly say there's no point, unless there's some feature you absolutly have to have. If your flying and building skills are advancing then a computer transmitter might be a good idea because eventually you'll need one. If you're happy with what you're flying it's not worth the money.
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Old 07-12-2004, 05:18 PM
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Default RE: Computer vs standard transmitter...

the following is taken from a document written by fellow microstar user Ted sander. here you can see just some of what's possible with a capable radio...you can also see that it can be a bit of a headache if you really don't need it...

dave

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MIXING

Mixing one “stick” channel to another (Ail, Ele, Rud, Throt) –
As tested, FROM = Ail, TO = Rud

Positive and Negative Gain settings reflect their respective “FROM” stick motion away from neutral.

Giving right Ail used the Pos Gain setting. Giving left Ail used the Neg Gain setting. Neither gain setting had any effect when the stick was moved in the “other” direction. Setting one of the gains to 0% prevented any output when moving the stick in that gains direction, while the other direction still functions.

100% gain gives you 100% throw of the “TO” servo setup.

When Ail is mixed to Rud, and both gains are at 100%, you will get the full range of motion programmed for the rudder servo, using the Ail stick.



Reduced or increased percentages in the Gain are proportional to the “TO” channels range of motion.

50% gain will gave 50% of the max rudder throw, in the example setup.



You can have asymmetrical motion.

Right Ail stick gives you 75% Right rudder, and Left Ail stick gives you 25% Left Rudder. Just a matter of setting one Gain to 75%, one Gain to 25%.



“From” Dual Rates/Expo do transfer to the “TO” channel.

Ail D/R of 50%, cuts the established rudder motion by 50%.

This is governed by the percent setting in the “From” (Ail) channel for D/R. Varying the “To” channel (rudder) D/R had no effect when mix was turned on.

Note that you will see the D/R percent of the “From” channel (Ail) applied to the “To” (Rud) output. Example: Ailerons move +/- 40º, Rudder moves +/- 60º (measured at the servo). Ail D/R is 30%. The end result is 30% of 60º, or 18º Rudder output.

Effect of Exponential is similar



“From” Trim is also proportional to the “TO” channel.

Both trims were at 10%. Gains at 100%. Ail and Rudder had differing end points. Result was 10% of Rudder throw, when moving Ail trim. Varying the “From” trim percent, changed the amount of trim applied to the “To” channel.



You can “reverse” the output motion by making the corresponding Gain negative.

If Right Ail normally gives you Right Rudder, controlled by the Pos Gain %, you can make Right Ail give you LEFT Rudder, by changing the Pos Gain to a negative value.



This allows you to have surfaces that always move in the same direction, no matter which way the FROM stick is moved (One Gain is a positive percent, the other is a negative percent), or surfaces that move opposite the stick motions (both gains are a negative value). Note that the “TO” stick would then produce normal movement, while the “FROM” stick would reverse it!



The mixing of both stick motions add together.

If moving the Ail stick gives you 100% of Rudder, and then you also move the rudder stick 50%, you get the servo moving 150%.

This can get you in trouble by exceeding maximum servo capacity, unless you have set your Min/Max as noted above.



Example: Rudder moves to 60º at 2.000ms. MAX is set to 2.200, which if we had setup the rudder servo to move to that endpoint, would have given 75º of motion. Mix gain is 100%. Aileron stick at full therefore moves the rudder 60º. Moving the rudder stick full would then move the servo another 60º, or a total of 120º of rotation! Bad things could happen, if that were allowed! The MAX setting limits it, and the rotation of the servo ends at 75º. This can also confuse you, if you forget that there is a limit imposed by the max/min settings!


“REPLACE” does just that. No input from the “TO” stick is accepted.

Mixing otherwise acts as described above.


Setting the ZP positive or negative shifts the “TO” servo center and endpoints a proportional amount.

Zero Point slews the endpoints and center of the output channel. Primarily useful for dialing out any minor shift when flipping mixing on or off. Test setup had the rudder servo move off center, and changed the endpoints, by 3º when the Mix 1 switch was flipped. Setting ZP to 6% cured that.



Interesting possibilities for shifting the center a large amount, zeroing out one gain, and putting in large % for the other.



Tables:

Tables are pretty easy. Just remember that there are 11 stick positions, from neutral to full throw. You can think of the “POS” settings as “Percent Of Stick movement”, where POS 0 = 0%, POS 1=10%, POS 2 = 20%, etc. up to POS 10 = 100%. The same table would also apply to the opposite stick travel, so for example, “Up” elevator has 11 positions, and “Down” elevator would use the same table and positions for it’s movement, also.

The percent you program in is a multiplier to that stick position. If you set all positions to 100%, you’ll get linear output. 10% output at 10% of stick, 20% at 20% of stick, etc.

But, if you do a progression, you get an exponential type output:

POS 1 at 10% means 10%*10%, or output of 1%

POS 2 at 20% means 20%*20%, or 4% output

POS 3 at 30% means 30%*30% or 9%

POS 4 at 40% = 40%*40% or 16%

And so on….


And, of course, don’t forget the gains! The above assumed that the POS and NEG gains in mixing were at 100%. If they were at 20%, you’d get for POS 1: 10%*10%*20% or output of 0.2% of throw. Not much!


Per cents for the Positions are like many other places in the Microstar – they top out at 128%, so setting up a reverse curve might be tricky (but I haven’t tried to drive them negative, to see what would happen. Interesting thought!)


Tables are also a solution for those odd mixings we like to do in fun fly type airplanes. One of my favorites is to do looping touch and goes (take off, loop, touch, loop, touch, etc.). Yes, very frequently the ground moves up two feet between touches, but that’s a geology problem, not my radio or flying skills! A big plus in this stunt is to reflex the ailerons up (making them spoilers) as the throttle is cut to idle at the top of the loop.

Setup would be: Setup ailerons to act as spoilers at low throttle, program a table so that percents are 0 at most of the positions, with the last (or last few) being high percents, up to 100% at POS 10. As throttle is cut, ailerons stay normal for most of the movement, but then rapidly deploy as spoilers for the final movement of the stick. Actual setup is a little more than that, but you get the idea…….


And, in testing, it was found that there is a glitch in being able to set the percent for POS 10 in a table. Doing it by using the transmitter results in no change to the parameter being saved. You can work around this by using the PC software interface. Then the value will actually change and operate correctly, but will not display correctly on the transmitter. Gordon will be correcting this in the next revision.



Indirection:

Gordon’s notes pretty well sum up this feature. By assigning a channel to Indirection, under a mixer, you then are able to vary the Pos/Neg gain, up to the maximum specified in the gain settings.

In a simple example, if you mixed Aileron to Rudder, but weren’t sure what your final gain should be, set the gains to be relatively high (50%??), and use indirection to have the Ch 6 slider adjust it in flight. When you land, if the optimum setting had the slider at it’s mid-point, you would assume that you were using a gain of 25% ((50% of the slider position times the 50% Pos/Neg gain). Readjust the gains to 25%, and then take off indirection.

Helicopter pilots and others with more complicated mixing scenarios I’m sure can think of multiple uses for this feature.

Mixing to the same channel:

This is where you can apply tables to a single channel! For example, if you want to set a curve for the throttle, to get true linear output of RPM :

When you have figured out the appropriate Table percent settings to apply to get equal increases in RPM at each stick position (an exercise for the reader!), mix Throttle to Throttle using your defined table.

A note of interest – If you do not choose “Replace”, your gains are additive to the original throws! This is the normal behavior as described above for mixing one channel to another.




Enough! The flexibility and adaptability of all the above parameters is astounding! The big lesson to remember is that “FROM” channels are interpreted as “Percent of stick (slider, switch) movement” which is then applied to “TO” channel servo timing values. These can be further modulated by percents of gain, indirection, dual rate/exponential and/or tables.
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Old 07-12-2004, 05:30 PM
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Default RE: Computer vs standard transmitter...

I would say that ZAGNUT has summed it up.
THe only thing I would add is that you probably will not control more than 5 axis or items at any one time but the ability to mix controls is the most important function.
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Old 07-12-2004, 09:46 PM
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Default RE: Computer vs standard transmitter...

With synthesized tx and rx, you use one transmitter to fly several panes. Just dial a channel and fly! Hitec, Futaba, and Polk make computer radios that do this. Oh yeah, what they said too!
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Old 07-12-2004, 10:28 PM
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Default RE: Computer vs standard transmitter...

Multiplex makes syth stystems too...
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Old 07-12-2004, 11:05 PM
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Default RE: Computer vs standard transmitter...

You don't need a synth module to fly multiple planes, only different frequencies. With the cost of entry level computer radios going down, they are becoming a very good investment for future projects.
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Old 07-13-2004, 07:48 AM
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Default RE: Computer vs standard transmitter...

You asked if the features were worth the cost. I promise if you get a decent computer radio you will not know how you got along without one. I learn't to fly on a very, very basic Am futaba set. This took a long time to set up models with and having two models was a real problem with having to send servos away to get reversed. When you have a computer radio you dont even think about these things. Let alone dual rates, mixing, expo etc, etc.
Also if you have more than one model, your controller is the only thing that you use for every plane.
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Old 07-13-2004, 09:58 AM
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Default RE: Computer vs standard transmitter...

Digital trim! Set it and forget it. No bumping sliders by mistake and finding out in the air.

Timer with alarm to set for landing when the fuel is getting low.

Store more than one plane in memory.
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Old 07-13-2004, 07:56 PM
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Default RE: Computer vs standard transmitter...

I think that the digital trims are what I notice the most evertime I pick up a non computer radio. Im so used to not worrying about accidently knocking them. That alone makes it worth it.
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Old 07-14-2004, 04:23 PM
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Default RE: Computer vs standard transmitter...

The digital trims alone make it worth it to me regardless of how many planes you are flying. Multiple model memories, programmable mixers, servo reversing, servo travel adjustments, dual rates, exponential, etc. etc. etc. The list goes on. If you're in the market for a new radio I highly recommend a digital radio. To me an analog radio is a waste of money. Spend a few (literally) extra bucks and get a computer radio. If money isn't a problem, and you plan on progressing in this hobby to more involved aircraft, spend $300 and get a great computer radio (Futaba, JR, Airtronics, Multiplex, Hitec, etc. all make great equipment). I have a Futaba 9c and love it. Good luck!
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Old 07-19-2004, 03:47 AM
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Default And to see the results....

Some computer transmitters show the servos to understand the result of a mixer. Others don't.
Anyway, if you are in doubt, want to show to others, a.s.o. you can see it on a PC computer connected to your transmitter.
See the (simple)PCM project in an 'Article' at [link]http://www.jdm-nivelles.be[/link]

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Old 07-27-2004, 11:50 AM
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Default RE: Computer vs standard transmitter...

I wrote an article for an internet magazine in May on standard radios for entry level flying. In doing the research for the article as well as research for a new radio for myself I have come to the conclusion that the only reason to buy a standard radio is lack of confidence that you plan to go forward, or the standard radio came as part of an RTF package. In the follow-up article which will come out in August, I take that exact position then go on for 9 pages discussing entry to mid level computer radios.

Here is a quick look at some key points.

Economics - forget the servos, receivers and stuff you need for each plane. That is the same regardless of the radio. I am talking about just the radio. For comparison, let's use a the Hitec Laser at $60 as an example of a standard 4 channel radio. Most of the standard radio advocates I have spoken to have one radio per model. That's $60 per plane.

Compare that to the Hitec Flash 4x as an entry level computer radio - $85. You get 5 model memories so you can instantly switch to any of 5 models without having to reset anything. Flash costs about $17 per plane and you only have to remember to bring one radio regardless of which plane you plan to fly.

So 5 models would cost $300 in standard radios vs $85 for the Flash 4X. Big savings!

Now look at functionality. Use a Hitec Flash 5X, a REAL entry level computer radio that can do things the standard radio can't. Costs about $110. You get channel 5 retracts but you can also use that fifth channel for other stuff.

Split Ailerons/flapperons: - You can put two aileron servos, one on channel 1 and one on channel 5. Fly the plane normally. Then flip a switch and turn the ailerons into flapperons. Now you can use your ailerons as flaps during landings. Flaps on a 4 channel plane that doesn't have flaps. Cool!

Coordinated turns - Mix rudder into your ailerons so you have a coordinated turn. On a standard radio you have to do this manually. With the computer radio, you focus on the plane while the radio handles the coordination yet you can override and add or reduce rudder at any time.

So, for an extra $50 over a standard 4 channel radio you get a radio that handles 5 models and let's you do things that the standard radio can't do. Will you need it on the first plane? Maybe not but you probably will in the near future, so why buy the standard radio in the first place?

Obviously this is only a small look at the capabilities of this particular entry level radio which has other features. Go up a another $40 and it is amazing what you can do. The price difference over a standard radio is now so small that for all but the very few, the computer radio is now the economic entry level radio of choice.

If you get into even semi serious aerobatics or sailplanes, a computer radio is a huge benefit and for some things, almost a requirement to bring the plane to its full potential. Even a 4 channel parkflyer benefits from a computer radio.

There is only one reason to buy a standard radio these days. "I don't know if I will like RC flying so I want to spend as little as possible", or it came in a package like an Easy Star RTF, a Great Planes Spirit Select RTF or a NextStar Glow RTF. Get a computer radio, save a bundle of money, get a bundle of features and really have fun with your RC flying.

If you want the links to the articles, let me know.
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