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Jun 15, 2019, 04:44 AM
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gazza2003au's Avatar
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Drone diy build under $300 GPS + FPV possible?

Hey guys is it possible to build a drone for under $300 with GPS and FPV including everything needed i also need a 30mins flight time for aerial photography, would like the GPS to have hold position, follow me and if possible the setting where the drone holds altitude and circles u

i was going to get a Parrot Bebop 2 for AUD$450 about USD$300 but i will be using it for aerial photography of my boat and fishing trips so if i submerge it i know i can find the parts cheaply to replace rather than trying to find a new main board for the Bebop

if anyone can help with links or advice or even u can tell me i am dreaming on a $300 budget i don't know much about drones i just know what features i would like in one, DIY is preferable to keep it within the budget

a drone in the 250 to 350 category would be marvelous for my budget
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Jun 17, 2019, 04:43 AM
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Seeing as you have to ask this question, I'm going to say that, regrettably, you're dreaming.
(I am assuming that anyone with enough technical expertise to build this(to the letter) would not have to ask.)

Now getting that sobering thought out of the way, here are some thoughts on the "project".

The big problems:

1. 300$ "for everything I need" - transmitter, video goggles/ground station and battery charger should be included in that price point? If so, this becomes... difficult.

2. Follow me, and circle object (especially a moving object) are still very rare features in the Diy realm, as far as I know only ardupilot has these features - ish (I use only betaflight/inav). And even then these features are not nearly as easy to use as the dji counterparts.

The less big problems:

1. 30 min flight time is no problem on ~450 class (10 inch props) quads - anything in the 900-1000 gram range (battery included) with 5000mah 3s battery should be getting somewhere around that. However going smaller on propeller size this quickly becomes an issue. Still - a 7 inch proped quad doing 20 min flights isnt a big challange. You might (emphasis in might) get better results with 18650 cells, but these aren't without their own challenges.

2. Arial photography means different things to different people, please clarify. Are you happy with onboard 1080p recording and standard sd video feed? Anything better than that becomes... difficult... to do within budget - hd downlink are probably still about 300$ by themselves... gopro and runcam/foxeer cams are 100$+... realistically - to get best flighttimes- I would go for runcam split or caddx turtle, but to me these do not really qualify for "aerial photography "

The no-problems:

GPS position hold, barometer altitude hold and even return to launch are all (relativly) easy to do. A cheap 20-25 $ omnibus clone (with barometer) along with a Beitan bn880 gpc/compass (about 20$) module will do these things
Last edited by Insufferable Oaf; Jun 17, 2019 at 04:48 AM.
Jun 17, 2019, 05:05 AM
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Thank Oaf for posting this information i am new to drones but not new to RC, I will buy a cheap drone with the features i want i really want the circle me, hold position and follow me because i will be using it for fishing from my boat that is where the lengthy battery time comes into play i can fly the drone out 15 meters and up 5 meters and have it hold position while the fish are on the bite and record it all for my youtube channel plus i want to take some aerial footage of my boats running along and possibly out in open ocean in the rough to record this from the air would be unreal footage

i am seriously thinking about buying the MJX Bugs 5w it has everything i want with a clear video to SD card its just a little bumpy from what i have seen on youtube but as i gain some drone experience i can look further into drones and all the equipment

the DJI range in Australia are out of my budget my budget is around $400 the DJI Tello is the only affordable model about $150. The DJI Spark starts around $850 however i love the footage from the DJI models they record so crisp and clear with no bouncing or anything very professional like
Jun 18, 2019, 04:00 AM
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Yes, is possible. Want a recipe?... more difficult

18650 will not bring any benefit if your platform isn't already capable of at least 45 minutes on lipo.
At 20-30 minutes, i.e. 2-3C discharge, LiIon perform worse than lipo, delivering less than 80% of stated capacity.

Get an used Bebop2, can be found even at half price of new.
Jun 18, 2019, 10:53 AM
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Hey Ren i was looking at the 18650 high discharge batteries 35amps running 4 packs 2 paralell 2 in series i think i got that right so 70amps max load at the 12.6v would need to run 12x 18650 cells that would be around 550-600grams but the capacity would be huge
Jun 18, 2019, 11:51 AM
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Is a nonsense to look at high discharge capabilities, because you want long flight time, i.e. lightest discharge possible.
The problem with these batteries is the voltage, that drop very fast over 1C, and the result is the low energy.
Everybody is fooled my looking at mAh which is a bogus unit, don't express anything, power is wattage, and you need power for flight, not mAh.
So when you compare apples with pears, please consider that average voltage of LiIon is 3.5V across all discharge curve, while for LiPo is more than 3.8V, 10% difference.
So you need only 3000 mAh LiPo to deliver the same energy as 3300 mAh LiIon.

2 LiIon in series is pathetic, you need a platform that is able to land at 5V, this is the final voltage you need to deplete a LiIon, in order to deliver all the state energy, are you sure you can handle this challenge ?
Jun 18, 2019, 12:38 PM
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I bought a DJI Spark but i do have a diy model f450 i bought 1 year ago no idea how to set up the naza software so never actually tried using the drone

I have been a lipo bloke for 20 years but the li-ion batteries have peaked some interest

I was looking at it like this single cell 3500mah 35amp rating in burst 20amp continous draw

Actually running 3 cells in series to give 12.6v than run 4 packs in parallel to give 14000mah if that works out i have been out of the hobby a few so my calculations may be a drift

A 5500mah 3cell lipo on ebay weighs 450grams, this li-ion pack 14000mah 12.6v charged will weigh 576grams an extra 126grams over lipo batterys for a little over double the capacity
Jun 19, 2019, 03:17 AM
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You are dreaming, or wrong math somewhat, based on wishful thinking.
Look at LiIon discharge diagrams, try understanding them, then redo the math for Wh, forget mAh.

I recently demonstrated to some fellows how a 4000mah 3s 345 grams lipo won against a 3s2p LiIon made using 3300 mAh cells, that weight 290 grams and triple price as the $20 lipo.
The real delivered capacity of LiIon was 2750 mAh at 1C discharge, at 2C was been worse.

The LiIon success stories you see are for planes drawing very low current in cruise mode, some 3-5Amps, or for multi-rotors that are already able to do one hour flights using lipo.
Jun 19, 2019, 05:36 AM
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Ok i will explain in a bit of detail here with links

Above battery rated 20amps continous 55amp burst

Single cell 4.2v charged, 3000mah each cell

Now if we take 3 cells in in parallel that will give us 12.6v and 3000mah

Now u make 4x 3cell packs and run them in series you will have 12.6v and 4 packs at 3000mah each is 12000mah

Basically you'll have a combined 12 battery cell pack 3 in parallel 4 in series as 1 combined battery pack

12.6volts 12,000mah weighing around 600grams with plugs and heat shrink

You'll also have 80amp of continous draw power with burst up to 220amps
Jun 19, 2019, 12:37 PM
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Again, top current rating is of no interest, drawing continuously 80 amps from a 12000mAh pack means 6.5C, thus less than 10 minutes flight time.

Ok, before looking for the right computation... first noticed a mistake in your post...

"Single cell 4.2v charged, 3000mah each cell

Now if we take 3 cells in in parallel that will give us 12.6v and 3000mah"
Really ?

And now back to math...
Did you notice in the graph that "4.2v charged" voltage is just for the record, because it drops immediately at 3.8V ? and also, average voltage across the whole curve is 3V ?
With these numbers in hand, we compute the energy stored in this pack:
12 cells * 3V * 3Ah = 108Wh
Next, computing the specific energy, aka density, 108 / 0.6 kg, gives us 180 Wh / kg, which is far from the 230-260 Wh/kg of batteries used for flight records, and is close or worse than high efficiency lipos used for multicopters.
For example the 8000mAh 4s 643 grams delivers 122Wh compared to the 108Wh computed above, due to the superior voltage of LiPo. Energy density 122 / 0.643 = 190, beter than 180 of the LiIons.

As a side note, today is wiser to avoid packs having more than 100 Wh, because they could be subject of banning from most aerial lines

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