Over the last 8 months I have been working on the construction of a micro-drone that weighs less than 250g, is capable of making autonomous flights and has a flight time of more than 20 minutes, aiming to improve the logistics for conducting academic experiments with drones and swarms of drones. After testing various motors, ESCs and batteries models, I got a configuration that met the initial goal of the project. Some members here collaborated with their comments in the article MicroArduCopter, 3" props, Omnibus Nano, Success! and I wanted to thank you for that (mainly @wicked1, @Hugues, @andyp1per, @Paul_Atkin1 and @rickyg32). The next steps will be to add the CX-OF optical flow sensor to improve stability and 4500kv engines to improve flight time. I recorded a video of the first endurance test after achieving a reasonable PID calibration. I recorded in HD, but YouTube is still processing the best resolution. Anyway, the flight time can be seen… Cheers!
Great work!
Could you tell me which esc? I see in youtube it’s a lumenier, but which one? blheli_S or 32?
It is this one: https://www.getfpv.com/lumenier-blheli-s-20a-4-in-1-bec-5v-1-5a-esc-dshot.html .
I ordered this one too, but it not arrived yet. I hope it will be a bit lighter: https://www.getfpv.com/lumenier-mini-blheli-s-12a-4-in-1-opto-esc-dshot.html . Both are BLHeli_S.
Congrats!
What components you ended up having on board, to get to 21 min? i see you also got pass-through telemetry stream working on the taranis - is it the yaapu script, or a different one?
Thanks, and yeah, the S versions all worked better for me, too, for low voltage.
Hi, Paul. I’m using Kakute F7 AIO flight controller with Yaapu script and FrSky passthrough option. The other components are Benewake TFMini LiDAR, mRo GPS+Compass. Motors are EMax RS1106 6000kv, but I will replace by 4500kv for improving flight time a bit more. The propellers are Gemfan 3025 2 blades. Another next enhancement will be the addition of a CX-OF optical flow sensor to improve stability. Maybe I will do it today and test tomorrow.
Yes… And all the BLHeli32 4-in-1 ESCs are heavier. The ligther one I found is about 20g…
The problem with this is that the interface is not UART, it is CAN, and Kakute F7 don’t have a CAN interface. I asked the developers of ProfiCNC to create one with UART interface, but they were not interested… 
i see. makes sense.
again, hypothetically, to cut a bit more weight off you can use omnibus nano with smaller gps and different lidar, but, even as is - nice results. nano still does not have software inverter solution, so it would need some creative methods to get telemetry working that may end up counterproductive, but, for such a small build it is difficult to say what would be of most importance - F7 rich features or nano small size and weight.
what battery is there, and what is model weight without it?
smallest 3" one i have now is the 160g with no battery, but it is a sport 4S build that uses 650mah lipo, an armattan gecko, FPV with nano and gps puck - no lidar and no telemetry. not even close to 20min range. 
Even with a serial interface the VL51L0X is not working outdoor, so your OK with the TFMINI and the Cheerson CX-OF
Yes, Nano was considered when I chose Kakute F7. It is a good and very lightweight option. The total weight of this micro-quad without batteries is 110g, including CX-OF optical flow sensor. I ordered 2 more new 4-in-1 ESC models weighing 4g, so, the weight can be reduced to 104g if some of these new ESCs does not have LVC at 3V. About the batteries… This is the hardest part. I tested 12 models of battery using Mountain Radio CBA IV Pro and the best results were obtained with Sony VTC6 18650 3000mAh. The problem is that this model have a lot of counterfeit in the market, actually, most of them are counterfeit, even at well known stores. The original one is now made by Murata, that have acquired Sony Energy some years ago. I got original ones with a local reseller in Brazil, but this is really hard to get.
cool!, setup is surprisingly close to my octo.
I have the 4500kv motors but with smaller 2534 props. My esc’s are 40a blheli32 so i could get some weight savings there. I don’t get anything like 20 mins flight time tho, more like 5. Not that I have tried really loading it down with a big battery yet, and using li-po rarther than li-ion. Was hoping for sub 250g but about 100g over. Quad is certainly better than octo for efficientcy.
Yes… Actually, I tried with VL51L1X from Pololu (I2C), that have the double range of its brother. It worked with the latest ArduCopter firmware, but was causing some conflict with telemetry pass-through. I think it is a ChibiOS issue. Now that I’m using TFMini, I will keep the VL51L1X to use as obstacle avoidance sensor for indoors operation, because it is extremely lightweight.
I can confirm that I tested both in parallel indoor and outdoor HereFlow Optical Flow Sensor Testing
and the VL51L1X from Pololu signal get ‘‘washed’’ outdoor
Cool assembly this octo! In my case, as the total weight is 210g, I can use 1106 4500kv motors (114g of lifting each) instead of 6000kv (185g of lifting each) and I still keep at least 2:1 propulsion/weight recommended ratio. The endurance can improve if you can use less motors. That’s why my next try will be a micro-tricopter… .
Hmmm… I flew only indoors when testing VL53L1X (not VL51L1X). It could keep a steady altitude in AltHold mode flying at 2m height. Now I have 6 units of them to find some usage. Probably I will use for obstacle avoidance… Do you think it will work? 
@iampete, btw, this GPS+Compass from Matek is too slow to get 3D fix. It took more than 2 minutes to get more than 12 sats, while mRo gets +15 sats in less then 30s. Is yours taking all this time too??
can be slow if you have not used it for a while, mostly its been great tho
