exploration drone - Page 1
Forum section: electronics / projects

author: basbr
author_rank: Newbie
timestamp: April 19, 2019, 11:05:24 pm
content: so i came across this planned NASA drone and thought, wouldn't it be cool to make something like that for earthim planning to make a autonomous quadcopter drone that has a GPS and can communicate with a raspberry pi, the raspberry pi will have 3G cellular modem with witch it can receive commandsand send photos (maybe even a video feed) back. the idea is that the drone can travel long distances in short hops and gather data/photos along the wayto recharge its battery's it will need to have solar panels. im aiming for one hop every 7 days (with optimal sun) and a range of 3 - 5 Km for a hophere is my current layoutim going for 4 x 2.5 W solar cells that give about 6V each. im going to have two sets of two in series to get 12 V to charge 2 x 2cell lipo battery'si also have a separate battery for the raspberry and other 5V electronicsto conserve energy during charging i am planning to cut off most of the electronics from the power supply and only turn parts of the electronics on when neededim also looking into a sleeping circuit to completely turn off the raspberry during the night or cloudy days.here is a rough draft (im only going to CAD when i have all components working)the camera will be used to take pictures when landed and looking down in flighti have build drones before so that wont be a problem. the raspberry isn't that hard either. but i have little experience with lipo charging.because this system will be on its own for long periods of time i want to use a balanced 2S charger, this seems to be a really rare thingim really struggling to find the best configuration here. the main requirement of this BMS is that its efficient and reliablehere are some questions that i still need to figure out-will it be more efficient to have a Boost Converter between the solar panels and the charger-what is the best configuration of the solar panels/battery-what motor/propeller works efficient at the chosen battery configuration-how to weather-proof the brush less motorsany input would be greatly appreciatedthis i just a hobby project so i am trying to keep it under 1000$i have a 3D printer that i will use to print the frame, i am currently testing out chargers with the solar panels

author: a59d1
author_rank: Regular Contributor
timestamp: April 20, 2019, 01:48:46 am
content: Your biggest problem will be power. Solar quadcopters have been built on Earth, but they all fall within a very weird envelope of being barely able to fly:The issue is that every gram of payload you add is a gram that can't be put toward solar cells. Either it flies for minutes a day, spending 99% of its time charging on the ground (with the Pi hibernating), or you discard the Pi in favor of some lighter-weight CPU and fly continuously. Anything like a robotic arm will be far too heavy for the quadcopter to handle.Also, think of the drag and instability created by those solar cells. The quadcopter can barely fly; if the NASA helicopter had any more solar cells in the propeller column, they would lose a good fraction of their thrust to turbulence.The NASA probe has several things going for it which we don't have:- Low atmospheric density, so airflow may be slightly more laminar than on Earth and thus more efficient (I am not certain of this)- Lower thrust and power requirements due to low gravity (38% of Earth)- Coaxial monocopter is passively stable, can have very large blades, and requires only one or two motors (reducing weight and power cost)- During times that don't have dust storms, the sunlight is constant and barely attenuated on Mars whereas Earth solar installations have to deal with clouds, trees, weather, and our thick atmosphere- NASA can afford to buy the most expensive and lightweight solar cells (GaAs is 37% efficient but silicon is <25%)- NASA has dozens of engineers working on their project, you seem to only have yourselfThe best thing you could do is copy the NASA helicopter as closely as possible and see how close you can get.These links may be helpful.http://www.starlino.com/power2thrust.htmlhttps://news.nus.edu.sg/press-releases/solar-powered-quadcopter

author: a59d1
author_rank: Regular Contributor
timestamp: April 20, 2019, 02:00:39 am
content: The basic premise of the NASA drone is that it's cheaper to move a camera a few hundred feet through the air on a drone than drive the multi-billion-dollar rover around on the ground. When you consider how much wear the wheels receive and how many scientists are relying on the rover for data (like dirt spectrometers, ultrasound, etc etc) this makes a bit more sense.I also just noticed that the drone weighs only 970 grams. That's absolutely nuts for something with a 1.2-meter radius propeller! RC helicopters on Earth with that much propeller cross-sectional area usually weigh 3-8 kilograms:https://www.xheli.com/align-kx0160npnt-trex600n-le-kit.htmlSee here for some details:https://www.nasa.gov/press-release/mars-helicopter-to-fly-on-nasa-s-next-red-planet-rover-mission.Also, I don't know how accurate this page is, but it claims the helicopter uses a Snapdragon SoM from Intrinsyc and ZigBee radios. Whether those parts will survive the radiation on the trip to Mars is quite another questionhttps://en.wikipedia.org/wiki/JPL_Mars_Helicopter_Scout

author: Rerouter
author_rank: Super Contributor
timestamp: April 20, 2019, 03:07:36 am
content: Good thoughts on the sleep circuity, I would use something like a low power micro to combine the sleep circuit, battery monitoring and power switching of each peripheral, to essentially shut things down until the next scheduled communication window, you could even let it share the modem to let it handle the comms when the rpi is shut down.This way it keeps power draw to an absolute minimum until your ready to fly,Per water proofing your motors, print a cup with a hole, place it over the motor shaft, screw down propeller on top of the cup, and use thread locker when putting on the propellors,Per the solar panels, yes a boost converter will work, you will want some capacitance before and after it, might be better if you just used an IC that charged directly off the solar, e.g.http://www.ti.com/power-management/battery-management/charger-ics/products.html#p1152=2;2

author: basbr
author_rank: Newbie
timestamp: April 20, 2019, 10:33:18 am
content: yes the idea is to have the drone on the ground for 99% of the time with one 10 min flight to a new location every week or so. if it gets to little power it can just spent longer charging or making shorter hops, im not in a rush. i might not have made it fully clear but i want this drone to operate fully autonomously while i sit at home and occasionally send new coördinats to fly to.it would be best to copy there design but they went for a bit of a unconventional design and unlike NASA i have to use of the shelf products. There are a lot more places selling quadcopter parts than mars droneseven though, autonomous quadcopters aren't unheard of, most newer flight controllers have things like "fly back to base" functions.i have the kakute f7 that im planning on using in this projecthttps://hobbyking.com/en_us/kakute-f7-aio.htmlas you say flying with those solar panels out can be unstable, that's why i going for a sort of sideways diamond shape to be hopefully more aerodynamic.If this turns out to be unflyable i might look into some sort of deployable array that folds up during flight.also im only planning to send it flying in optimal conditions (low wind speed/tail wind)Most of the things that i'm planning to do have already been done before on there own.-communicating with a raspberry over 3G-flying a drone autonomously with GPS-charging lipos with solar cellsi'm just putting them all together in one projectAnd if something fails, my drone isn't on another planet. so a rescue mission is a lot easierThanks for you input!

author: basbr
author_rank: Newbie
timestamp: April 20, 2019, 10:44:07 am
content: maybe a low power micro is a good idea, the ADC only draws 2mA so it could keep check on the power level continually.i was planning to print out essentially upside down cups to put over the motors but i thought that they might get to hot that way.so i would like to add some sort of air schoops in them like you see on power toolsas for the charger i was hoping to stumble upon something premade, i got some parts in the mail that i'm going to test to see if they will work for me.this one:http://www.modmaker.co.uk/Micro-USB-2S-Balance-Charger?search=chargeri might just have to bite the bullet and make my own charger circuit.

author: Rerouter
author_rank: Super Contributor
timestamp: April 20, 2019, 10:58:01 am
content: Low power micro would be the best for while its landed, have the solar charger just constantly in circuit, even moonlight can charge provided the charge IC can scavenge from the lower voltages.Build it around the basis of using almost 0 power while your landed, have the micro wake up every few minutes, check the voltages and then go back to sleep, and every X of those wakeups maybe send a telemetry update.Use logic level P channel mosfets, so that grounding a pin causes it to turn on, where as most of the time a pin pullup can keep it off,Equally for most micros, the power down mode does not alter the I/O states, meaning you can benifit from very low >0.2mA power down modesIn the past I have instead of using a watchdog timer to wake it up, used an external RTC with an output pin, set it to change its output every minute and done my polling based on that. then when the battery voltage gets high enough, and the RTC says its daytime, you wake up the rest of the power hungry systems and do your next hop.If you can look for flexible solar cells, the main thing is you want to either fly slowly so your angle is pretty shallow to the wind, or shape the body so its surface area is low for the angle you will be flying at for your ideal speed.