Newb needs advice

[squarjn]

This is my first attempt to build a quadrotor. My goal right now is to build something that can fly, with a very low budget, preferably under $150. Later I will probably make a larger investment to build a better multirotor, but for now I'm just interested in the learning process/building something that works.

So I have a frame that is about 25 cm. in diameter and together with arduino weighs about 5 oz, I might be able to make it 3 oz if needed.

So I was wondering, if I was to get 4 motors like this:

http://www.hobbyking.com/hobbyking/...ing_Donkey_ST2004_1550kv_Brushless_Motor.html

and 4 ESPs like this (I do need one for each motor, right?):

http://www.hobbyking.com/hobbyking/...0A_Fixed_Wing_Brushless_Speed_Controller.html

and a Li-Po battery like this:

http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=6307&aff=588847

Would that work? Are those motors strong enough to lift the quadrotor?

I happen to have a bunch of these props (clockwise and counterclockwise versions) I could use with the motors:

http://www.wowhobbies.com/blh7520_propellerclockwiserotationblack2-1-1.aspx

So if I get all those parts, attach the motors to the frame and ESPs which I power with the battery and control with the Arduino, using a gyroscope and accelerometer, will I get a working quadcoptor? Are there any glaring flaws to this plan?

 

[ProPilotWannaBe]

squarjn,
I have never piecemealed an MR together, so I won't be able to help much. However, I will answer a couple of questions you had:
1) Yes, you do need one ESC per motor.
2) From the little I read on the HobbyKing website, those ESCs are under powered for those motors. If you read the comments on the website, they recommended 18A ESCs, and those that you picked are 10A.
3) I don't think that battery will last you long. I have a totally different setup (DJI F450 stock), and a 3S 2700mAh battery only last me about 10 minutes. So you may want to consider a little bigger.
Hope that helps a little...
Tim

 

[squarjn]

Thanks for the reply. I think I will look into getting a bigger battery. I saw those comments on the ESCs, one was "Maximum motor current is 10 A. 12A ESC should be enough, but I recommend 18A." I'm a bit confused... does this mean that 18A ESCs are better equipped to supply 10A motors, or does the motor actually draw more than 10A despite what is listed on the spec sheet?

 

[Electro 2]

Good rule of thumb is to design for double the expected current, so, 20A ESCs. That said, it's hard to predict what you'll be pulling until test flights. On my 585mm I designed at 5A per motor, it actually worked out to about 7A or so when optimally propped. I used 25A ESCs, too, they get comfortably warm during flight, never hot. AOK.

"Would that work? Are those motors strong enough to lift the quadrotor?"

Also a conceptually flawed statement here. Motors don't lift frames, the batteries do. They do so by suppling electrical energy to the motor, which converts it (at some loss) to rotary torque. The torque, in turn, rotates the propeller which converts the energy (at some loss) to displaced air, which is what lifts the aircraft. Every component in the chain has to be correctly specifed for reasonable function, not just the motors. Ultimately, in multis, it's watts vs weight. For motors the question is are they able to convert the total power required for flight within their power ratings. This is usually revealed by their power curves published by the manufacturer. Look for a "Grams per Watt" figure with a specfic size prop, figure out how much this aircraft is going to weigh, factor in a thrust-to-weight of about 2-to-1 divide by 4 (faor a quad) and boom, you've got your motors reach.

 

[squarjn]

Thanks for explaining that, I think I understand what to look for in a motor now. It looks like the motors I'm looking at produce between 180 and 360g of thrust depending on prop and battery, so since my quadcoptor will probably weigh about 400-450g that should be good enough.

 

[Electro 2]

All this said, I don't have any design experience with what I would call "micro sized" multis. I'm accustomed to tossing around numbers for much bigger craft, say 5-10 lbs. So you're going to have to do some design work on your own to get optimal numbers for this one.