Before I begin, an apology. I think anyone who starts their own website, blog, etc. does so with the best of intentions to post regularly. I admit to being slightly remiss in that respect; forgive me readers for I have sinned … it has been 34 days since my last quadcopter post …
So that out of the way, where were we? In the last part the rotor arms had been fastened to the bottom chassis plate and the motor power leads & main battery connector soldered to the plate. Time to introduce you then to the FC … or Flight Controller. This is the brain of the quad and even the cheapest FCs offer pretty remarkable features and processing ability. For anyone who fancies digging a little deeper, I recommend this page on Oscar Liang’s excellent website.
Below is the FC I purchased for my build, mainly because it was the closest I could get to the one used in the HackSpace article. It’s not the smallest or the most powerful but it’s pretty cheap and has all you’ll need for a beginner’s craft. The mounting centres are at 31.5mm so that should give you an idea of its overall dimensions.
Here it is installed onto the bottom chassis plate with 3mm nylon stand-offs and rubber grommets in the mounting holes to help absorb some of that ever present vibration.
Time for a brief aside me thinks … please feel free to skip if you like! The observant amongst you will have noticed the ARM logo on one of those chips above and ARM has a history that started when I was first getting into computers at school. For those in the UK of my age group, cast your mind back to the early 80’s when the BBC embarked on a mission to get the nation computer literate and commissioned the BBC Micro which was made by a British company called Acorn Computers. Founded in 1978, Acorn developed a RISC (reduced instruction set computer) processor and the company eventually became ARM Holdings whose ARM architectures can be found in smart phones, digital TVs, set top boxes, mobile computers and, of course, flight controllers! From the Wikipedia entry above: In 2013, 10 billion were produced and “ARM-based chips are found in nearly 60 percent of the world’s mobile devices” … that’s a pretty impressive track record in anyone’s books.
To those who read my little aside, thank you very much. And those who skipped it, hey I won’t hold it against you. Back to the build and the first wiring to connect to the FC was the main power feed, which you can see is picked up from the internal PCB tracks of the chassis plate making routing cables much easier and neater.
Then came the tricky part of connecting the control wires from the motor ESCs. Two problems here; the solder pad on the FC for the control wire is roughly 1.5mm diameter if you’re lucky & close to the FC mounting holes (necessitating removal of the nylon screw nearest the pad so as not to melt it with the soldering iron) and space is limited for access. There’s also the age old problem of not having a 3rd hand to hold the wire in place whilst holding the soldering iron with the 1st and applying solder with the 2nd! When I was researching connections for the ESCs I saw a post where the constructor had coiled the wires to allow some resilience to vibration, which I thought a good idea. It also looks pretty trick, to coin a ‘yoof’ phrase!
And that’s it for Part 3. The next & final build post will look at the radio control receiver, finishing off the build & a little setup I knocked together to calibrate level for the gyroscope on the FC.