new brushles micro built


date: 2017-08-31 07:56:40

tags: quadrocopter Drones

category: drones

Created by: Stephan Bösebeck

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new brushles micro built

I do own quite a lot of drones now, as you can read and see here for example. Especially the tiny whoops below 250g got my attention - not only because that with the new regulations for drones, everything that is lighter than 250g can be flown FPV without a spotter.

I do have 2 of those lighter 250g ones and a couple of brushed racers with 6 or 8mm brushed motors (like the eachine QX95).

But brushed motors do have their disadvantages and fortunately the brushless motors get smaller and smaller... So I built a small 90mm brushless quad racer:


These are the parts:

  • Awesome E90 Frame from Bangood
  • XJB V2 PBF3 EVO from Banggood, FC, 4xESC and PDB all in one (or better: all-stacked)
  • Motors: BGNing 1104, 4000kv - available from amazon
  • AIO Camera VTX, could use the Eachine TX01 - also available from Amazon. I used a no-name one, that I cannot tell where I got it actually emoji github:smirk
  • FrSky XSR Receiver, available at Amazon

of course, you need some props and a buzzer and cable and zip-ties for mounting etc. But it was not too complicated to built, although there is not much room there...

Telemetry FrSky Taranis with Betaflight boards

This is pain in the ass! It took me ages to get that running. The problem is, that FrSky need an inverter for their protocol to work on the UART. So, if your FC does not have an inverter for your UART, you are screwed...

But, if you do a bit of research, heat up your soldering iron, it is not so hard to get done. You need to follow the instructions here, which explains where to solder one or two little cables on the XSR for this to work.

It is not that hard, you need a magnifying glass, calm hands and a very pointy soldering iron emoji github:smirk

But what really drove me crazy is the fact that, even after all this soldering action, that godamned thing did not work at all. But as usual, the problems was in the settings.

You need to open the betaflight console and disable the software inversion: set tlm_inversion=OFF otherwise it would not work. And do not forget to call save afterwards.

keep that in mind after updating!

Then telemetry worked fine!

The lipos

I did not want to have an additional connector and dedicated lipos lying around here. So I usually do only have 4s Lipos and for the brushed ones 1s of course. As I have a lot of 1s batteries here, I wanted to make use of them. So I soldered one cable that creates one 2s Lipo out of two 1s lipos (putting them in Serial, quite easy actually.) Soldering it was not that hard, but it was freaking me out connecting a red wire to a black one...



So with this cable I can use the lipos of the blade Inductrix. And I do have telemetry, so I know how things are doing...

As soon as I lift off, the voltage of the lipos dropps down to about 7V more or less emediately. The mini racer flies well, but the voltage is dropping.

I do have a similar problem with the AcroWhoop - read here - I think the lipos do have some fault or they are at the end of the lifetime. I will use some replacement lipos and see how that goes.


This is a very much fun little racer, not too expensive and easy to handle - especially in small areas. I did get some new lipos, but as the voltage measured goes up again after landing immediately, I decided to lower the warning levels to 6,8V and 6,6V. With that I can fly about 4 minutes with 2x 600mAh lipos...

first time flying outside in the "wild" is available on youtube - raw dvr footage