kaos wrote:Ok from another angle to look at this. say the resolution is the steps you can move the servo. can you move that stick 1/200 of the whole travel precisely? let alone 1/500.
Yes absolutely, watch the little video I'll post later.
But most importantly there aren't only sticks, on modern radios there are many things that alter the stick -> output relation. The resolution, as meant in radios, means the total number of steps the servo signal will have
in its standard 1000-2000us range. So basically a 512 step system will have a 2us resolution, a 1024 step system will have a 1us resolution, a 2048 step system 0.5us resolution. So this number of steps is valid IF you use the entire range. So for example once you start using limits and D/R's to reduce movement, you'll reduce that number of steps. Let's say you have a 50% D/R. You lose half of the steps, BUT that smaller number of steps is still mapped to the same amount of stick travel. So if you had a 1024 step radio, and set 50% D/R, the stick->servo response is now that of a 512 step radio.
Then when you fly your aircraft, you rarely use full throw, the most important part is the center, and if you hold level flight you'll do little corrections in only a small range of the stick, maybe 10%, but those have to be precise. To help with that, you have expo. As you can't indeed be infinitely precise with your finger, but the model needs precise adjustments on the controls around the center, you use expo to reduce sensitivity close to the center, and precisely be able to make use of that increased resolution. Those 10% of stick movement will now result for example in only 5% of servo movement.
And of course trim. A small number of available steps means that each step is big, and you can't do any fine adjustment. You'll see in the video that with a cr*ppy receiver that had bad firmware resulting in low resolution it was simply not possible to trim the plane, FPV makes it MUCH more obvious as you're a LOT more aware about what happens up there and thus more precise on the controls than in normal flight. As the servo steps were big, the ailerons would either be half a click to the left, or half a click to the right, impossible to fly straight. Same as servo horns, with their big teeth they are never where you want them when you install a servo in a model, but on one of the sides.
http://www.youtube.com/watch?v=PY0WiKeM-uQ
As you can see at the beginning with the good receiver how by moving the stick slowly I will move over every us on the output. That's 1024 steps being useable already, and with 100% end points and no expo.
And again, the resolution has no relation to the response time. Let's say you're in flight, and want to stop your plane perfectly level. You don't have to find the exact right step instantly, but can do it over as much as several seconds. It's "automatic" so you're not conscious of it, but you will progressively correct and move your stick more and more, and probably trim too, until you find just that good step. It doesn't matter how long it takes, but the resolution allows you to reach that position. If you don't have the resolution, that position simply won't exist, and even if you could try for 2 days you would never get your plane to fly straight.
