Solving the BIG PROBLEM I have with DIY Drones!
.. … This video of mine is from 2016 6 years ago and over the years, this harmless joke turned into a bit of a stress nightmare for me because while I actually started working on 2 prototype drones, I never finished one., But people demand a DIY drone video and I honestly want to deliver one as well, because I think dronesquadcopters are quite fascinating and definitely fun to play. With. And getting parts for a drone is also not hard.. I mean there are thousands of flight controller boards, electric speed controllers, motors propellers and LiPo batteries on sites like Amazon, Ebay or Aliexpress.. But exactly that was my big problem, because when you mix a random motor with a propeller ESC and battery, then you can never be 100 sure at what RPM the motor creates a specific thrust and with what kind of power demand and efficiency. This goes along. Because of that I always realized way too late, that my motors were either too small or too big for my drones weight, and thus I never achieved an optimal mix between my power electronics components.. But I want to change that and luckily a company sent me a rather professional drone motor test stand half a year ago, which I will finally put to good use in this video. To answer all my drone setup questions. And since the test stand is sadly rather expensive. I also decided to turn this video into a DIY or Buy episode, in which I will also show you how to build a crude DIY alternative test, stand that can do a bit less, but still enough for your own Drone tests.
Lets get started. This video is sponsored by Keysight who are giving away over 100.000 in oscilloscopes for free as part of the Keysight Live from the Lab virtual event.. All you have to do is sign up using the link in the description and by the way, youll also get a bonus entry for using this link., But its more than just a giveaway, because there you can see industry experts talking about super interesting electronics topics, and You can actually also see me there, so dont miss out.. First off. Let me present you my random assortment of drone power, electronics, parts featuring 4 different BLDC motors 2 speed controllers and 2 propellers.. Now I didnt decide on a battery yet because, like I said before, I have no idea what kind of combination firstly requires what kind of power to create a certain uplift thrust and, secondly, is most efficient.. The reason why that is important is that when you are running on battery power, you obviously want as much of the electrical power as possible converted into the desired mechanical power to maximize the flight time.. And if you are thinking, I should just use a bigger battery which comes with more energy to increase flight time. Then let me tell you that a bigger battery is obviously heavier than a smaller one, and thus the drone requires more power to lift it once again. Decreasing the flight time., This example shows well that keeping the weight of all components in mind is also very important.
. And last but not least, I didnt decide on a battery yet because I am not sure what voltage levels the motors require to create sufficient RPM and thus thrust.. By that I mean that, by going with the labels on the motors, you always get a kV rating which multiplied with the applied DC voltage gives us the maximum RPM they can spin with. And since right now I have no idea what RPM represents. What thrust? I am not sure whether I need a 2S 3S4S and so on battery and by the way, the S stand for series and tells you how much LiPo cells are combined in series in the battery pack to increase its output voltage.. So there are a lot of parameters I am interested in that my Buy or DIY test stand definitely needs to provide.. That means it was firstly time to have a look at the buy option, which came with a pretty easy to understand manual that helped me assemble. The test stand within an hour.. The way this system works is that the main PCB measures, the voltage and current applied to the ESC, as well as how fast the motor spins, by observing one of its wires, and also how much a load cell gets deformed by the thrust force created by the Motor., And since it is important later on, a load cell is basically an aluminium profile onto which 4 strain gauges are positioned and connected together in a Wheatstone bridge configuration whose output voltage changes depending on how much we deform or how much weight we put on it.
. I know this sounds a bit complicated, which is actually why I made a dedicated video about the topic, but in a nutshell, the load cell, outputs, a voltage proportional to the force its deformed with and thus by calibrating it with a known massforce. We can measure unknown massesforces., But moving on with the test stand for now, which should be able to measure all interesting electrical and mechanical values., And thus, after calibrating the load cells with the help of the provided software, it was time to attach the first motor with The first propeller hook up the first ESC, powered by a 2S battery replacement, get the ESC control signal from the test, stand PCB and give it all a try.. As you can see, everything seems to work just fine. So what I did first was gathering data to find out which speed controller is more efficient., And I think it is pretty easy to spot in these 2 diagrams that show how much electrical input power. We need to create. What thrust that ESC 2 is a bit more efficient, which is why I continued doing all the other tests with the remaining motors with it.. So after collecting all this data, I am also happy to reveal that propeller 1 is apparently more efficient than propeller 2 by creating the same thrust with less input power.. Next, I was also able to create this RPM thrust graph and Power thrust graph, which made me think that motor 3 is the most suitable one for me.
, Because with the set 3S voltage range, which I am definitely favoring for my final drone build. It was able to lift close to 400g, so 1.6kg, with 4 motors in a quadcopter setup. And best of all motor 3 is also the lightest one, while still featuring a pretty good gW efficiency compared to the other motors.. And if you are wondering why motor 2 and 4 created such low thrust values, then let me tell you that low kV motors should get powered with a way higher voltage, which my speed controller would not have survived., But anyway, with these results. I am a lot smarter now what my favorable power, electronics combination is and can offer, and thus I will hopefully this time bring my drone build to an end. Before doing that, though, lets build a super cheap, DIY drone test stand alternative that you can build at Home. Now the electrical input values we do not have to measure, because every lab bench power supply can do that. And for the mechanical side we can just add a 3kg load cell to an aluminium profile for the base and to a motor mount on the other. Side., So to put my plan into motion, I firstly designed a motor mount in fusion360, which I then 3D printed with some PLA.. While that was going on, I used M5 bolts to mount one side of the load cell to the aluminium profile. And as soon as the print was finished, I secured it to the other side of the load cell with the help of M4 bolts.
. Next, I soldered the load cell wires to an HX711 24 bit Analog to Digital Converter, which I also hooked up to an Arduino. And to the same Arduino. I also connected the control wires for the ESC. After then, writing a bit of code to generate the ESC, control signal and outputting the load cells amplified voltage. We can see over the serial monitor that we are reading a voltage that reacts with how strong I push onto the load cell brilliant. Now, with nothing on the load cell. The reading is around 218700 and after placing a 200g weight onto it, the reading is around 361050, which is a difference of 142350 for 200g, which means a difference of 100g should be around 71175, and thus our load cell is now calibrated. To prove that I tried Out a known setup from before and recorded the values for different, specific control signal values.. If we convert those values into a weight, we can see that the DIY version is pretty close to the values I recorded with the commercial version, which means my DIY setup can do this job, just fine as well.. Of course, it is also a lot cheaper, but, on the other hand, not nearly come with as many features as the buy version, which is why I have to say that for me, both DIY and Buy are this time the winner., But no matter what option you Choose I hope you now understand the trouble I went through before with my drone builds, and I am very happy to have a proper plan now to continue so stay tuned for the next drone video.
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