Taking Stock

I've now decided on all the specific parts of the drone.  A big thank you to the eCalcs website in helping me with all the calculations!

So the decision:

Motors: 
High torque is good for efficiency.  I learn electric motors are measured in turns per volt, so a nice low kv motor will be fine :)  This is complicated only by the number of manufacturers out there! The good side is healthy competition so these great motors are not too expensive!

It's a bit "suck it and see" however the eCalc website tells me the Turnigy Park450 motor is good.  It's on the higher price side $16.45, that's OK as I'd rather have a good flight time and reliable motor!

Battery:
Here's the compromise already.  In a previous post I'd decided the battery.  On reflection I think two 5000mAh batteries are too heavy, so then I looked at 4000mAh.  Great, I looked at my lovely spreadsheet and found the right battery, wrong.  The 4000mAh battery was out of stock as was the 5000mAh battery :(

The compromise, I've gone for two Zippy 3700mAh batteries.  What does that mean?  Roughly 1.5 mins less flight time.  Never mind, at least I'll have the batteries soon for development rather than waiting.

One thing to note, the Zippy brand from Hobbyking are the lowest quality so will give up at around 100 charges ... but they are the lightest!

Electronic Speed Control
These control the motors from my Gadgeteer board.  It needs to respond quickly to powering up the motors, with a low internal resistance to save power and avoid overheating.

I've chosen the Hobbyking Blue Series 20A, motors go up to 14A.  Why this model?  It's meant to be a fast responding ESC and light weight.  We'll see.  It's on the higher price side at $10.37 however this might just keep the drone from crashing!

Propellers 
Easy one.  The eCalcs says for my drones weight with the particular motor I'll have that 10" propellers are best.  Ideally I'd like black propellers however they were out of stock, lovely bright green ones instead.  I'm sure I'll get used to it!

Captain: Signal the Motors

How to get the Gadgeteer signals to the ESC to control the motors?

The ESCs need Pulse Width Modulated (PWM) signals to then control the motors.  PWM is relatively easy to understand and there's a great webpage on Wikipedia.

The Gadgeteer board I have gives outputs PMW signals so life is good :)  Apart from the usual problem, not enough ports on the Gadgeteer board!

Along comes my friend!  Pulse InOut from GHI Electronics.

What's lovely about this board is that it can support eight input and output PWM signals!  

I only need the four output PWM signals however I'm thinking perhaps the inputs could be used for ultra-sonic sensors to help automated landing and/or obstacle avoidance.  That'll be for later on in the project :)

Wonderfully, the Pulse InOut board indepently generates it's own PMW signals from a command rather than forwarding on a signal from the Gadgeteer board.  Why is that cool?  

If the code on the Gadgeteer board hangs then the motors still get their signals!!!  I love this fail safe(ish)  approach!!!

Safe Landing

Perhaps I might (later on) code for the chip in the Pulse InOut board for the case if the Gadgeteer board code does hang.  

I'm thinking along the lines if the Pulse InOut does not receive any PWM commands from  the mainboard for say 10 seconds then it gives equal power to the motors to hover and then slight decrease in power to enable landing.

Buying Time

I can't wait to get the board and start coding for it!  I placed the order with Proto-Pic a few days ago and being Easter there will be a few extra days wait.  Hopefully it'll be here before the weekend!  Yea!!!

Time to lock down the design?

Time to take stock!!!

Lots of learning over the last 5 days.  There's a lot in my head right now, many thoughts about the pilot control of the drone ... must write that down.

The electronics coming which will be fun, there's more learning there!  Last part of the puzzle is connecting the Electronic Speed Control (ESC) to the Gadgeteer Mainboard.  Definitely do-able, so I'm not worried.

Once that is done, time to lock down the design.  I can't believe in 5 days this has gone from impossible to possible.

What's Needed in an Airframe?

Here's a few things I reckon I need ... will be fun to look back in a month and see how it has changed!

• Lightweight ... I can't afford Carbon Fibre so Aluminium looks good
• Strong ... one I don't want it to break on the first go!
• Structural Integrity -  I want to minimise vibrations ... that will do the sensors no good.
• Storage ... somewhere to hold the electronics, batteries and camera

Sounds a tall order ... time for more research!

I reckon the Motors and ESCs now not hard to decide on after yesterday!

The final electronics are tricky to decide.  I have a theoretical idea on how many sensors are needed however that all depends on how the real machine flies.  Let's just have some fun :)

Mystery solved ... Airframe, Motors and Control!!

Oh how fantastic!!!!  I knew I was missing something!!!

I came across this top website where it lists components that other's use, excellent!

Also there's links to other hobbyists who on their webpages list the parts they use ... I am so lucky, I love the internet age!  FYI, here's one hobbyist and here's another :)

Where I was going wrong?

I had over specified the motors, then needed over specified Electronic Speed Controls (ESCs) and also looking down the wrong path for the ESCs.

It's so easy to go down the wrong path, I was so locked into checking robotic websites and component sites that I had neglected radio controlled hobbyists.  These guys need electric motors with ESCs and there's bucket loads of affordable offerings!!!

10 or 12A motors be fine! Then ESC cost only $12 each.  Even then a 30A ESC cost < $20 each.  Oh brilliant!

I'm so happy!!!  I can get an airframe (still need to decide), I know I have a solution for the motors and yes I can get affordable ESCs, what a result of a day!

One more question:  How to interface the ESC to the Gadgeteer Mainboard?

Getting expensive ... Motors, ESC and interface boards

Ummmm ... still no further in solving this problem!

Brushless motors are efficient however they need expensive electronics to control them.

Do I go for brushed motors?  The control electronics are cheaper, is this a compromise I have to make?

I am missing something.  I've seen toy quadcopters sell for £300 and claim they have brushless motors  There must be cheaper control electronics.

To complicate the matter, I'm looking into interfacing the Gadgeteer computer into the motor control, doesn't look easy.  More research needed!!!

Question of Motors ... ummm I need an ESC!!!

Motors, this completely new to me and I really don't have a clue.

Firstly, let's go electric ... everyone on the net is using electric motors.  I could go for a petrol engine yet that seems overkill, maybe one day :)

So electric motors, I know there's two types ... brushed and brushless.  I found a great little here, cool guide for topping up your knowledge!

What I did learn?  Brushless are more efficient than brushed.  Yep, need efficient motors for flying ... great lets go for that!!!  But which ones?

Well I saw on this site that these motors are recommended, are they good?  I don't know but it's a good start.

How much power do I need?  

I don't know!  I've learnt brushless motors are measured on Revolutions per Volt.  Then it all comes down to how much amps it can take.

I fancy powerful motors!!!  I am a guy after all :)  30 Amp current motors look kick ass, lets have them!

How to control them?

Ummm, no idea.  I've seen on the Gadgeteer site there are Motor Control boards however typically that is just for motors up to 3A.  I need something more.

Trouble Ahead

Oh dear, I've just wasted 4 or so hours!!!  Brushless Motors work by fancy electronics to reverse magnetic field to make the motor turn.   These seem to be called Electronic Speed Control, ESC, systems.

Here's the trade-off, efficient motors require expensive ESC electronics to control them!

The downside, a single motor controller that "just" does 10A costs $100 USD.  At least on this website, the next is a 60A controller and that is $275!!!

I'm new to this, $275 x 4 motors = $1100.  One of my aims was not to make this an expensive project, this is not the right direction.