New 250mm Build Project (cont.)

Using XSR+ receiver and Taranis X7.

Set my BetaFlight Receiver tab like this: (from Not sure which parts are essential there.

This was essential, though… BetaFlight Configuration tab, set Receiver to “Serial-based receiver (SPEKSAT, SBUS…)” and Serial Receiver Provider to “SBUS”:

Bind procedure is to power receiver while holding down button in upper left, then using “[Bnd]” from Page 2 in my model’s configuration on the Taranis. I’m using the “Internal RF”, set to D16 mode. Powering receiver like that will give a flashing red light. Binding will make the change the light; cycling power will give just a steady green light on the receiver.

Changed Channel Map in Betaflight “Receiver” tab to “TAER1234”. This seems to be my default.

Channels 1-3 are rock steady at 1500 with no mod. Nice. Throttle shows 987-2011 by default.

Going to power up everything and see how the transmitter plays with the quad next.


Needed to enable switches on the Taranis so that they would be available in BetaFlight. Thanks to @UAVfutures:

I set up modes like this, though I don’t yet have a beeper installed:

New 250mm Build Project

Frustration with getting the ESCs to work. Built with:

  • 250mm Frame
  • F4 Revo FC
  • Matek PDB
  • Racerstar MS-Series 15A ESCs
  • EMAX XA2212/980KV Motors
  • GemFan 5030 Propellors
  • FrSky XSR+ Receiver

Wired motors with CCW ESCs wires switched; CW were wired straight across.

Fitting the components on this frame was a challenge as well, as the PDB wasn’t designed with the frame cavity in mind. Also, the PDB called for 3-4S, so my 2S batteries were going to sit this out.

Wiring the FC was also troublesome, though all on me. First time installing pins, chose the ESC connections for this method. For ESCs, I only needed Ground and Signal, so I cut up pins for the top and bottom rows of vias. The spacing for the female connectors to the pins was too tight to fit the connectors adequately, so that took some adjusting.

I avoided a potentially huge mistake. I got turned around on the schematics when wiring up power to the FC, and mistakenly wired two positive vias on the FC to the 5V feed from the PDB. ESCs wouldn’t start up properly, USB said the device was drawing too much power, even measuring the PDB feeds to the FC would come up with just millivolts. Finally, I corrected that, and was then able to make headway on my ESCs.

Trouble with the ESCs… random attempts at getting proper protocol selected, finally got it to MULTISHOT, and then calibrated in BetaFlight.

Initially, this FC was flashed with RaceFlight, but with all the trouble I was having, I flashed down to BetaFlight. I think I can still go back to RaceFlight since all the problems were of my own making.

Big lessons on motor mounts needing to match frames, btw. I had ordered some Kensun 1806 2300KV motors, but while the prop shaft was the correct size for my 5″ props, the closer pair of screw holes in the motor were too narrow for my frame; this was after ordering this size motor based on suggested from the frame’s product page.

I’m punting here, using my old EMAXs, my first El Cheapo brushless purchases, along with the ESCs which were Christmas 2016 specials, no longer even listed on Banggood. In order to use the EMAXs, though, I drilled out my 5″ props to fit the larger prop shafts… we’ll see if this was a good idea, I worry about the balancing of the props.

Overall, good practice soldering. I was surprised over and over at how resistant to re-melting my solder joints were. Even with flux, tightening my solder iron… 370° C didn’t seem hot enough. I didn’t change the temp, though, just worked through things slowly, getting more of a feel for working with solder in its various states.

I attached the FrSky XSR+ receiver that was installed on the used Atom V2 that I bought. This will be the first attempt at binding with a Taranis, the first time I’m using a protocol other than DSM2/DSMX. The Rx is wired, and powers up. This is my next step.

Here’s a pic with props dry fit:

Smaller quads can use satellite receivers


@burtlo: Providing redundancy for a main receiver is why satellites were originally created. On a large plane with CF structure (which shields RF signals), you can place several satellites around the fuselage, to make sure your expensive giant scale plane can always receive a clear signal from your TX, no matter its orientation.

However, modern multirotor FCs can now “speak” the serial protocol that satellites use to talk to the main RX. So the FC can communicate directly with the Sat RX. In addition, there are now satellites with diversity, i.e. two separate RX circuits and antennas. This adds redundancy in the satellite itself, so you don’t really need the main RX. That is, unless you want to add redundancy to the redundancy to the redundancy. :wink: Only giant scale guys or jet flyers need/want that to protect their multi-$1000 investments (and innocent bystanders on the ground).