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ET BL_Beta75 Build

 

Here's my build of a 75mm micro quad using brushless 0703 motors and the Beta75 Pro frame.  Features of this quad:
 For this build I used Full Speed 0703 15000KV motors.  They have ball bearings and run well, but don't come with connectors and the motor-mount holes on the frame need to be enlarged to fit them.  At this point the BetaFPV 0703 15000KV motors (which come with connectors and don't require frame modification) are probably the best option, but I haven't used them myself.  BetaFPV says they are now an "upgraded version with bottom ring and shaft welded together."

The Beta75 Pro 1S Brushless BNF copter sold by BetaFPV is very similar to this.  What's missing from that one are the configurable VTX (via SmartAudio) and the two-way FrSky telemetry (F.Port).

See below for a full parts list.

See here for a gallery of pics.

 See here for a video.

The weight (complete) without battery is about 30g.  (The stock Inductrix+ weighs 35.5g.)

Flight time with a 1S 600mAh battery is 5-6 minutes.

Notes:

I used the TBS Unify Pro Nano 5G8 video transmitter (VTX), which supports SmartAudio for configuring the frequency and power output, and I used the TBS Tiny Camera, which has a 5-volt regulator.  So, the battery power is connected to the Tiny-Camera board, which then supplies 5-volt power to the VTX.  It makes for a very light and tidy setup.

The VTX SmartAudio configuration support requires a connection from the smart-audio pin of the TBS Unify VTX to the "TX" line of a UART on the flight controller.  (See here for info on SmartAudio.)  The BetaFPV flight controller does not provide pads for the extra UART lines, so a wire needs to be tack-soldered onto the necessary pin.  The UART3 "TX" line is pin 21 on the F3 processor (see pinout).

I used 36AWG teflon coated wire.  The main trick is to use rosin flux.  If you put a bit of solder on the end of the wire, tape the wire in place, brush on some rosin, and apply heat from a fine-tipped soldering iron, the solder should flow into place.  (I use this Rosin Flux Pen.)  I installed a wire onto the "TX" line of UART3; see here for a pic.

With the VTX setup for SmartAudio configuration, the video frequency can be configured using the on-screen video display and the R/C transmitter sticks; see the SmartAudio CMS OSD guide in the Betaflight wiki for more information.  The video frequency may be set using band/channel values, or to a frequency in MHz.  Starting with the v3.3 release of Betaflight, the video frequency may be configured using VTX CLI settings; see here for info.

In this build I'm using an FrSky R-XSR receiver with its firmware updated to the F.Port Protocol Firmware.  (See here for a good article on updating FrSky receiver firmware, and here for info on F.Port.)  For F.Port the TX line of the UART is needed, but the BetaFPV flight controller brings out the RX line to the pads for the receiver.  The (fairly) simple fix is to connect together the TX and RX lines (for UART2) at the F3 processor, pins 12 and 13; see here for a pic.

I shorted the length of the antenna leads of the R-XSR receiver by cutting and splicing them; see here an article on that:  https://oscarliang.com/repair-2-4ghz-antenna-rx

With a receiver connected via F.Port (or SmartPort), flight controller and VTX settings can be configured via 'lua' scripts on a Taranis / OpenTX transmitter.  (See here for 'lua' scripts and here for good info article.)  I found that it's possible to set the VTX frequency while the flight controller is powered via the USB port and the VTX is not transmitting (because the battery is not connected) using the Taranis or the VTX CLI settings, and then have the frequency be applied when the copter is restarted.  (Be aware that after the change the VTX will transmit at the "old" frequency for a second or two while the flight controller is booting up.)

To get an RSSI (signal strength) indicator for the receiver, a configuration needs to be setup in the Taranis that routes RSSI to a RC channel.  The method in this article worked for getting RSSI directed to a channel, but the range of values was not right.  (The 'rssi_scale' setting in Betaflight seems to have no effect for this type of setup.)  To fix the range I ended up directing the RSSI to a spare channel (CH26) and then to the channel that goes to the flight controller (CH16), applying weights and offsets along the way:
   * Taranis:  Input - create "rss" / RSSI input (weight=100)
   * Taranis:  Mixer CH26 with Source=(I)rss and Weight=500
   * Taranis:  Mixer CH16 with Source=CH26, Weight=360 and Offset=-85
   * Then set Betaflight RSSI Channel to AUX12 (CH16)
Also, to get it so the RSSI is displayed as 0% when the RC signal is lost, in the Betaflight Configurator Failsafe 'Channel Fallback Settings' do AUX12="Set 1000" (or set in CLI:  rxfail 15 s 1000).  With these things setup you can get a nice 0-100% RSSI displayed on the video OSD.

I installed my props with rotation opposite the orginial Cleanflight "standard," as I think they are more efficient that way, so the configuration needs to have "yaw_motors_reversed = ON".  I found that the stock Inductrix FPV+ props ran a bit more smoothly than the BetaFPV 40mm props.

See here for a flight-controller configuration I've been using (in the settings directory).

See here for my Taranis Q X7 transmitter-settings file that includes this model.

Betaflight version 3.3.0 or newer should work well with this quad.  I've been flying a beta/devel version that includes modifications for "extend crash-flip mode #5163", "IMU accel convergence after disarm #5425", "corrected CLI to allow vtx_band=0 #5465" and "Turtle/Flip after crash: Add options to use all the motors #5600"; the source code is here and the hex file is here.

Note:  If you're flashing speed controllers with BLHeli via ESC pass-through, don't do it with this beta/devel version of Betaflight on the flight controller -- use Betaflight v3.3.1 instead.  See the issue about this here.

Parts List:

BetaFPV F3 Brushless 1S Flight Controller (ESC + OSD) $29.99
https://betafpv.com/collections/flight-controller-1/products/f3-brushless-1s-flight-controller-esc-osd

BetaFPV Beta75 Pro Micro Brushless Whoop Frame $4.00
https://betafpv.com/collections/frames-props/products/beta75-pro-micro-brushless-whoop-frame

BetaFPV Canopy for Tiny Whoop Quads $2.00
https://betafpv.com/products/blue-canopy-fro-tiny-whoop-quads

FrSky Ultra Mini Redundancy Receiver – R-XSR $19.99
https://www.frsky-rc.com/product/r-xsr
https://www.fpvdirect.com/frsky-r-xsr-ultra-mini-redundancy-receiver.html

TBS Unify Pro Nano 5G8 (SmartAudio, 1.4g) $24.95
http://team-blacksheep.com/products/prod:tbs_unifypro_nano
https://www.fpvdirect.com/tbs-unify-pro-nano-5g8.html

TBS Tiny Camera $17.95
http://www.team-blacksheep.com/products/prod:tbs_tiny_cam
https://www.fpvdirect.com/tbs-tiny-camera.html

600mAh MyLipo 1S Battery $8.80
https://www.tinywhoop.com/collections/batteries/products/600mah-mylipo-1s-battery

Prop Set (8): Inductrix FPV + (BLH9605) $7.99
https://www.horizonhobby.com/prop-set-%288%29%3A-inductrix-plus-fpv-p-blh9605

Turnigy High Quality 36AWG Teflon Coated Wire 1m
https://www.hobbyking.com/hobbyking/store/RC_PRODUCT_SEARCH.asp?strSearch=36awg


Motor Options:

BetaFPV 0703 15000KV Brushless Motors (qty 4) $46.99
https://betafpv.com/collections/micro-brushless/products/0703-15000kv-brushless-motors

Full Speed 0703 15000KV 1-2S Brushless Motor for Racing Drone $10.99
http://www.fullspeedrc.com/15000kv-1-2s-brushless-motor-for-racing-drone_p0112.html


Alternate Parts:

BetaFPV 40mm 4-blade Micro Whoop Propellers $2.50
https://betafpv.com/collections/frames-props/products/40mm-4-blade-micro-whoop-propellers-4-sets

AKK AIO-SA (SmartAudio, 4.4g) $16.99
https://www.akktek.com/akk-aio-sa.html

AKK Nano2 (SmartAudio, 2.4g) $14.99
https://www.akktek.com/products/vtx/akk-nano2.html

Boldclash F02 Separated Type VTX Camera FPV AIO Antishock/5.8GHz/48CH/25mw/Male
http://www.boldclash.com/boldclash-f-02-aio-camera-for-tiny-whoop-fpv-inductrix-p7.html

Pololu 5V Step-Up/Step-Down Voltage Regulator S7V7F5 $4.95
https://www.pololu.com/product/2119

BetaFPV 550mAh 1S Lipo HV Battery (2PCS) $12.99
https://betafpv.com/products/550mah-1s-lipo-hv-battery-2pcs



For charging the batteries I like using TP4056 charging boards with PH2-connector pigtails attached.  The boards have a nice 1-amp charge rate; the pigtails can be cut off the 6x charging harness (see below for links).  The boards should be covered with clear heat shrink or packing tape.  They can be connected to USB wall warts, or to a multi-port charging station.

20X TP4056 5V 1A Lipo Battery Mini USB Charging Board Charger Module  $5.99
https://www.banggood.com/20X-TP4056-5V-1A-Lipo-Battery-Mini-USB-Charging-Board-Charger-Module-p-1095077.html

2 Pin JST to 6 x E-Flight Ultra Micro plug Charging Harness  $2.00
https://hobbyking.com/en_us/2-pin-jst-to-6-x-e-flight-ultra-micro-plug-charging-harness.html

5 Pack Lot 1Ft 1FEET USB2.0 A to Mini B Printer Camera Cable  $5.18
https://www.ebay.com/itm/350813005988

Key Power 60 Watt 12A 6-Port USB Charger Charging Station  $19.09
https://www.ebay.com/itm/183007999637

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ET Heli