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Originally Posted by nehalita
okay, from what i know, encoders, gyros and potentiometers - they are very useful to programming.
has anyone managed to do the autonomous code without using these?
and if we were to use them, where exactly does each part go? i know the potentiometer is for the arm, but where exactly?
where does the encoder and gyro go?
and which encoder/gyro/potentiometer did everyone use? i looked up the encoder from grayhill (61k/4k) and most of the places were sold out. i finally found one but it was a 61k256 which is too much, we just want a 61k64 and that too it was like $70+! we want something cheap and still useful.
thnx. i looked all over but most forums touched on the topic. hopefully this will help ppl with the same qs.
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Neha,
Autonomous mode can definitely be done without encoders, gyros and pots. There's dead-reckoning and copy-cat approaches which provide means to do pretty useful autonomous modes. I'll leave the copy-cat explanation to someone who's actually done it.
Timed dead-reckoning - Run pwm01 and pwm02 at 180 for 5 seconds, then run pwm01 at 180 and pwm02 at 140 for another 2, then stop. After a lot of tweaking and adjusting the speeds and the times, you can get your robot to park behind the center goal, stopping your opponent from capping with the vision tetra. There's quite a bit of useful stuff you can do, however don't expect to do anything too accurate, like cap a vision tetra, with timed dead-reckoning.
Encoders - for your drivetrain, you want to mount these in a way that when your wheels spin, so will your encoders. I've seen some teams put them on idler gears, or extend the shaft coming out of the gearbox a little bit, slip some flexible tubing over it, then slip the shaft of the encoder into the other end of the flexible tubing. We are using the Grayhill 63R256 from DigiKey, however they are now sold out. (Sorry, although we only bought 3, knowing that 600 other teams would be needing these)
Potentiometer - same idea as the encoders, you want your pot to spin when you run the motor that moves your arm. The difference is your pot has LIMITS on it, meaning that you can spin it only a few degrees in each direction. There are multi-turn pots, but these too have limits on them, but are often easier work with (less gearing). Your arm too should have some movement limits on it - i.e. you can raise it a maximum of 12 feet high. The goal is to have your arm and pot hit their limits at about the same time. When you've done this, you can setup limits on your arm so your operator doesn't over/under extend it, and you can even automatically slow down your motors when you get near your limits. Normally, we'll use limit switches in addition to pots to check our limits just in case. For mounting them, a popular way is to put a gear or sprocket on the motor that runs your arm, and put a gear/sprocket on the pot and attach them.
Sorry I didn't answer all your questions, but I'm don't much like to comment on things our team personally hasn't tried or done.
-SlimBoJones...