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DIY FPV Inductrix+ Build


This article describes my DIY build based on the FPV Inductrix+.  The stock Blade Inductrix FPV + from Horizon is a really good quad; it flies well and is durable.  The things I wanted to get in my own build were:
The thing the stock version has that this one doesn't is "meow" mode (which allows you to flip the quadcopter back upright after a crash by quickly reversing the motor direction).  Potential remedies for this would be to go to a build with brushless motors, or for a vendor to come out with a flight controller for brushed motors that supports reversing the motor directions.

I used the stock Inductrix+ frame, BetaFPV F3 Brushed Flight Controller (which has built in OSD and FrSky receiver), and CL-8020-14 motors from MMW.  See below for a full parts list.

See here for a gallery of pics.
See below for an FPV video flying this build.

The weight (complete) without battery is about 41g.  (The stock Inductrix+ weighs 35.5g.)

Here are some other weights:
  TBS Unify PRO 5G8 V2 Transmitter + BoldClash camera = 5.1g
  TBS Unify PRO 5G8 V2 Transmitter = 3.5g
  BoldClash camera = 1.6g
  Buzzer = 0.9g
  Stock canopy = 2.0g

The motor diameter is 8.0mm (not 8.5mm), and the motor-to-motor distance is 75mm (diagonal).

Flight time with a 1S 600mAh battery is about 4 minutes.


The CL-8020-14 motors are a very tight fit going into the frame.  I used a heat gun to warm up the mounts and motors while pushing them in.

I used the TBS Unify Pro 5G8 video transmitter (VTX), which supports SmartAudio for configuring the frequency and power output.  If the SMA-antenna-pigtail connector is replaced with a micro linear antenna, the weight is about 3.5g.  The VTX is mounted vertically, and a slot is cut into the canopy for it (see pic).  I found that if the VTX was mounted with its 4-pin connector near the flight controller, the VTX would pick up noise when the motors were run.  Flipping over the way it is mounted cleared up the noise.

The VTX SmartAudio configuration support requires a connection from the 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 (or wires) 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 wires onto both the "TX" and "RX" lines of UART3 so I could have the option of connecting a bluetooth module; see here for pics.  I ran the wires to a two-pin Micro-JST-1.25 socket connector

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.  With the upcoming v3.3 release of Betaflight, the video frequency may be configured using CLI settings.  More info and a development build supporting the new CLI settings may be found here.

(At first I was looking at using the FuriousFPV Stealth VTX, but didn't use it because it seemed to only support the fixed set of 40 channels, even when being configured to other frequencies in MHz).

The BetaFPV flight controller provides a +5V supply that should have enough power to run a 25mW video transmitter and micro camera.  The TBS Unify Pro 5G8 VTX can run at 25mw or 200mW (or even higher), so I wired a a Pololu S7V7F5 5V regulator from the battery to the +5V for the VTX and camera.

I had on hand a Boldclash F02 Separated Type Camera/VTX, so I used the camera from that combo.  It fit into the stock canopy mount (with its connector facing upward into the canopy).

A buzzer can be connected with the buzzer's positive lead wired to the red LED on the BetaFPV flight controller and the buzzer's negative lead wired to ground.  See here for a pic of the connection.  I used a CUI Small Buzzer CX-0905C.

The two-pin Micro-JST-1.25 socket connector I soldered onto the BetaFPV F3 board to the 'Camera' and 'VTX' pins would have been better as wires to a connector, as a connector there tends to collide with part of the canopy (the camera-mount post).  With squeezing and nudging I got it to fit, but it's tight.

Update:  On my original build I had the prop rotation opposite the original Cleanflight "standard."  With the way the motor supports on the frame are angled, the air flow is more efficient for the "standard" rotation, so I switched to that (by moving the motors and swapping which motor connectors are used; 1 <-> 2, 3 <-> 4).

The BetaFPV F3 flight controller is mounted with its USB connector facing forward so it is clear of the battery-mount part of the frame.  The 'align_board_yaw' setting is put at 180, and 'resource' commands are used to map the motor connectors.

See here for a minimal configuration set, and here for a configuration I've been using (in the settings directory).

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

Parts List:

BetaFPV F3 Brushed Flight Controller (Frsky Rx + OSD) $40

Main Frame: Inductrix FPV + (BLH9603) $7.99

Canopy, Black: Inductrix FPV + (BLH9604BK) $9.99

Prop Set (8): Inductrix FPV + (BLH9605) $7.99

CL-8020-14 coreless motors qty4 (speed: fast) 8.0mm $30.00

TBS Unify Pro 5G8 V3 (SMA) Video Transmitter TBS-UNIPRO-V3 $39.95

Micro 5.8G FPV VTX Antenna IPEX 55mm $1.99

Boldclash F02 Separated Type VTX Camera FPV AIO Antishock/5.8GHz/48CH/25mw/Male

Pololu 5V Step-Up/Step-Down Voltage Regulator S7V7F5 $4.95

CUI Small Buzzer (9.6MM radial) CX-0905C Digikey 102-1285-ND $2.28

Micro-JST-1.25 sockets (4) $1.00

10 Sets Mini. Micro 1.25mm T-1 2-Pin JST Connector with Wire $4.50

JST Battery Pigtail 12cm Length (10pcs/bag) $2.15 

Turnigy High Quality 36AWG Teflon Coated Wire 1m

Battery options:

Turnigy Graphene 600mAh 1S 65C LiPo Pack w/JST  $8.22

600mAh MyLipo 1S Battery  $8.80

E-flite 3.7V 500mAh 1S 25C LiPo (EFLB5001S25UM)  $12.34

Turnigy Graphene 750mAh LiPo Pack 1S 65C w/ JST-SYP-2P  $9.00

Turnigy nano-tech 750mAh 1S 35-70C Lipo Pack  $2.99

To hold the 750mAh packs onto the frame, pieces of velcro can be taped to the bottom (see pic).  Battery pigtails can be attached to TP4056 5V 1A Charging Boards to create cheap and easy chargers.


ET FPV Inductrix+ at Turn4 2017-12-19

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ET Heli