ArduCopter build - Guidance needed

A group of colleges and I are working on a Quad rotor for a school project. When Arducopter project showed up, we decided to follow it and create our own Arducopter. Most of the things in the Arducopter project wiki are very clear, and very easy to follow.

Parts already purchased are:

ArduIMU mega shield the old version
Ardu Pilot mega

4x SuperTigre 400 class motors here is the specs for it from flybrushless.com.. only 52 grams :D

4x 10 by 3.8 props (pusher/puller) (9x3.8 is ideal but I cant find the pushers anywhere!! )

: DX7 Tx and AR7000 Rx

Parts yet to be brought:

4x speed controllers - pretty easy to get them, but Question is, Do all 4 speed controllers have to be the same? my reasoning is that since all the ESCs are standardized to work with hobby Rx would it really matter if they are the same?? I'm probably wrong but is my reasoning correct?( because of stock issues locally, I might have to order online.. and shipping is a pain)

Battery-  I want to get about 20 mins of flight time, the weight is somewhere around 1200g, so going with 400g max thrust on each motor, about 1600g thrust which draws about 6.5 amps each.
If I go with a 2200mAh battery thats a approximate flight time of  0.08 hours (2200/26000) but of course this is an over estimation. Also weight is a factor, bigger batteries are heavier so, looking to go with a 4000mAh battery that weighs about 340gs. Anyone has any tips on battery selection?

Magnometer - the 5v regulated one was out of stock, the ones I can find are 3.3V (the ones at sparkfun)  so can I still use it with the arduIMU mega as described in the build logs, but I have to provide a 3.3V source for the Magmeter?


The Frame build

We are using aluminum tubes and aluminum sheets to start the build, probably move to carbon fiber tubes later. Here is the awesome part, we have access to a 3d printer, so we are printing the motor mounts and the stackable modules. have to see how the weight on these parts are like, hopefully its not too heavy.

also building our own power distribution board, just like the one available on the Arducopter project.

looking forward to your comments and Guidance

Pictures as we build, post I will 


Cheers.

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Replies

  • if you want to fly as long as possible, why didn't you use high quality motors with at lest 85% efficiency?
  • here is a build photo.. u can see the 3d printed motor mounts.. our custom made power board... didnt turn out so nice so, im going to make it out of regular wires instead.. will do that within the week..

  • With 10X4.5 prop at 10.7 volts your motors produce 765 grams of thrust. :)
  • Developer
    Welcome to world of ArduCopters. Over all your setup looks rather ok. What makes you think that 9x38 prop would be ideal for your case? I'd say that for 1200gr quad minimum prop would be 10x38 or maybe even 10x45. If your motor max thrust is only 400g, do not expect 20 mins flight times.

    Full ArduCopter which uses 850Kv motors, 10x45 props and weights about 1000gr can fly around 10 minutes with 2200mAh 3S lipo. And motors what we use gives 450gr already on 50% of their capacity. In general good rule of the fist is that try to go at least 1:3 ratio on weight vs. thrust. That way your motors have enough reserve to compensate quick moves like compensating wind gust and things like that. If your motors already run 80-90% at hover time, there's no way to make it fly properly and you might crash it easily.

    Mainly we use 2200-2800mAh batteries but also 4000-5000mAh. Naturally with 4-5Ah battery you can get closer to 20 mins of flight time. Flight time is overall compromise of weight, size, motors, escs, batteries, wind, how crazy pilot is and few other things.

    It is possible to use different ESCs, Motors, Props in anyways their characteristics differ a bit but then you would end up on having problems especially on hover. Biggest problem to have different ESCs is that when you calibrate min/max throttle values. That should be as same as possible for all ESCs due program code will use those values to scale it's motor output and if scaling is different, well you have a lot of problems. Even tho they are common devices and do same thing, their internal program codes differ a lot.. Again as rule of fist, keep them all same and it saves you from many trouble.

    As for magnetos, it is not just Vcc voltage you need to be worried of. You also need to have a level shifters due if you put 3.3v magneto to 5v I2C bus you will kill your magneto eventually. So I would suggest to wait untill DIY has those again on stock due on DIY magneto there are also level shifter on board along with voltage divider. And this level shifter has to be bidirectional. You can make your ArduCopter to fly nicely without magneto too, when you move more towards GPS assisted navigation and other GPS functions then magneto will get more important role. On normal flying you don't need it due yaw gyro holds really nice.

    I would suggest to stay on aluminum arms due they are a lot easier to work with. Cuting carbon tubes often breaks them if you don't have proper tools or proper knowledge to cut them. As one my friend says: "Ah playing again with those expensive lead pencils are we?? :)"

    Having a 3D printer is always nice :)

    Happy building....
This reply was deleted.

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