ImpulseRC Apex Micro 3" - 6S - DJI HD

By JosephTan on May 09, 2021

8  1,279  4

Inspiration for this build was seeing the Emax BabyHawk II HD 3.5” micro drone with integrated Caddx Vista / DJI HD video. I wanted to build a tough micro drone that would withstand crashes (better than my heavier 5" drones), have good flight characteristics and digital HD video.

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The build started on Monday 19 April 2021 (the day that the Ingenuity aircraft first flew on Mars), so this micro drone was bestowed the name “Ingenuity”.

The aim of the build was to achieve:

  • Micro drone size (3-4” propellor).
  • High quality digital HD video (Caddx Vista with Nebula Pro camera).
  • A durable frame for less frame resonance and better flight characteristics.
  • No propellors in view.
  • 6S power.
  • All up weight 250 grams (actual all up weight with 6S battery was 285g).

The frame chosen was the recently released ImpulseRC Apex Micro. With 4mm thick arms for a light weight drone swinging 3” propellors there is excellent frame rigidity. Camera needs to be adjusted slightly forward and no props are in view.

The ImpulseRC Apex micro 3” arms are installed with the arms furthest out (dead cat configuration) with the centre arm locking piece horizontal. Do not try and fit the arms with the locking piece longitudinal. I made that mistake on my first attempt.

High quality digital FPV video on a 3” micro drone was a definite design goal and the Caddx Vista with Nebula Pro was chosen as the video transmitter.

I am sticking with my old FrSky ACCST system for my short-range/non-GPS aircraft, so I chose the FrSKy R-XSR and flashed the latest F.Port firmware and updated the XJT internal module firmware on my FrSky QX7. Antennas were mounted on the front arms, horizontal orientation pointing back.

The Caddx vista was installed on the rear section of the ImpulseRC Apex frame using four 2mm bolts with plastic spacers at the bottom to avoid touching the carbon frame. All heatsinks were installed (did not want to sacrifice long-term reliability for weight saving). The cable running from the Caddx Vista to the camera was the default 12cm length, and this was swapped out for a 8cm Caddx HD cable to reduce cable slack.

The Flight Controller (FC) and Electronics Speed Controllers (ESC) was a single board IFlight Beast F7 (version 1.0). A 35V 470uF capacitor was installed along with the XT30 pigtail. A 25x25mm to 20x20mm adapter was 3D printed to fit the board.

The FC was mounted in a traditional orientation, requiring a yaw orientation offset to be applied in BetaFlight (45 degrees on yaw) as the board is a whoop-style board. The ESCs are rated for 45A per motor, this micro drone at maximum punch-out throttle consumes 9A (max) per ESC (swinging HQProp triple blade T3030 propellors).

The FC includes an F7 processor, internal current meter and runs on four 45A-rated BlHeli_S “H” ESCs. The firmware was flashed to the latest version of BetaFlight (4.2 at the time) and JESC firmware on the ESCs to provide 48kHz PWM and bi-directional DSHOT 600 capability for RPM filtering.

Motors picked were the Emax RS1408 2300KV rated for 6S operation, these deliver plenty of power for this micro drone. A variety of propellers were flown and evaluated: bi, triple, quad and cinewhoop-style quin (five) bladed props. For me I was happiest with the HQ Durable Prop T3X3X3 props (with the T-mount fitting to suit the motor).

Finding a suitable battery was the tricky. I found ChinaHobbyLine (CNBL) 70C 450mAh 6S packs with a weight of 85g. These work well and so far have been reliable but there will be voltage sag when drawing 700-950W full throttle (triple and five bladed props).

The ImpulseRC Apex Micro frame kit does not include a vTx mount for the Caddx Vista antenna, nor does it include the 25x25mm FC mount. These will need to be 3D printed. Links to these parts are below.

A generic GoPro mount was printed which adds around 7 grams of weight, but I left it on permanently (even when not running a GoPro) as it also protects the top plate.

Useful 3D Printed Parts:

ImpulseRC 25x25 to 20x20 adapter
https://www.thingiverse.com/thing:4748006

Official ImpulseRC Micro Apex Printable Files
https://www.thingiverse.com/thing:4732418

Universal GoPro mount (no locking nut)
https://www.thingiverse.com/thing:4769943

BetaFlight 4.2 PID settings:
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Photos

Part List

Frame

Micro Apex 3" Frame Kit (3 builds)
Impulserc.com
$71.04

Flight Controller

Beast F7 45A V1.1 AIO (MPU6000) 25.5x25.5
Shop.iflight-rc.com
$81.99

Motors

4 x EMAX RS1408 2300KV-3600KV Brushless Motor For Micro FPV Racing Quad
Emaxmodel.com
$51.96

Propellers

HQProp T3X3X3 (2CW+2CCW)-Poly Carbonate
Hqprop.com
$2.29

FPV Camera

Caddx Nebula Pro Vista Kit (7 builds)
Caddxfpv.com
$165.00

Receiver

R-XSR - FrSky - Lets you set the limits (5 builds)
Frsky-rc.com
See Site

Batteries

CNHL MiniStar 450mAh 22.2V 6S 70C Lipo Battery
Chinahobbyline.com
See Site

Radio

Taranis Q X7 - FrSky - Lets you set the limits
Frsky-rc.com
See Site

Goggles

DJI FPV Goggles V2 (161 builds)
Store.dji.com
$569.00

3D Printed

ImpulseRC 25x25 to 20x20 adapter by ImpulseRC (2 builds)
Thingiverse.com
See Site

3D Printed

Official ImpulseRC Micro Apex Printable Files by ImpulseRC (4 builds)
Thingiverse.com
See Site

3D Printed

impulserc micro apex gopro mount by aiemluca
Thingiverse.com
See Site

Misc Supplies

MG Chemicals 422C 55ml Silicone Conformal Coating For Waterproofing Quads MG422C-55ML [DG]
Phaserfpv.com.au
$20.09
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Discussion

Sign in to comment

overdeq   Jan 10, 2022  

nice build, do you have the caddx vista also conformal coated?

JosephTan   Jan 10, 2022 

Caddx Vista was not conformal coated. It is a good suggestion though! The FrSky receiver had a heatshrink wrapped, but no conformal coated either.

As of Jan 2022 this build has been running strong and have no major issues (even after many crashes, I've only had to replace props and a snapped off vTx antenna). Definitely one of my favourite quads.

overdeq   Jan 10, 2022 

yeah im still thinking about whats the best way to get the caddx vista waterproof
i also have a 4 inch apex and im super happy with it, its my little bando basher :D

FazerFPV   Oct 19, 2021  

Thanks for this, just the FC adapter i was looking for.

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