Professional Front End Engineer. Unprofessional tinkerer.

Gremlin Quadcopter 3"

21 Jun 2018

What is this?

A cheeky night vision quadcopter with a nice long range.

After the failure of my 3D-printed frame attempt, this one is a vague rebuild but with a tasty sparrow frame, mean props and most importantly a beast of a night vision camera (but please ignore the printed training wheels!)

It can’t record video, as it has a RunCam Owl 2 (intended for larger quadcopters) in this, a mini frame, so it’s crammed to say the least! I hacked and bodged the 26mm wide camera into a frame with 19mm of room, and am pretty darn chuffed about it for two reasons: 1. It’s a fantastic camera, 2. People in a quadcopter fb group I frequent said it wasn’t possible.

Not the best build in the world, as everything’s always on a budget and it’s heavier than it ought to be but it does benefit from a punchy battery so it’s quite nippy. Not to mention a huge video transmission range so it should make for fun twilight flights across the fields.

Key Ingredients

  • FRAME: GEPRC Sparrow GEP-MSX3 145MM 139MM Mini Frame (Stretch X) (£33.99)
  • MOTOR: 4 X Racerstar Racing Edition 1407 BR1407 3500KV (£23.39)
  • CAM: RunCam Owl 2 700TVL FPV Camera (£33.00)
  • FC: EMAX SKYLINE F3 Flight Controller (incorrectly priced! (£3.99)
  • ESC: Racerstar RS20Ax4 20A 4 in 1 Blheli_S Opto ESC 2-4S (£19.28)
  • TX: TX526 40CH 25/200/600mW Video Transmitter (£14.00)
  • PROP: Gemfan Tri-Blade Propellers 3052 x12 (£9.99)
  • BATT: TURNIGY BOLT 850MAH 3S 65~130C (£6.13)

Total: £150

Future Improvements

There are a few obvious improvements:

  • Better motors
  • Better vision
  • Lighter

With motors, you get what you pay for so these aren’t.. great (a couple even smoked-and-broke straight away). Vision could be improved with a burst of infra-red which I might try by using a circular array I have knocking about somewhere..) and I certainly could make it much lighter as the FC and RX are totally oversized for a mini quad. Even the TX and aerial are overkill but hey ho! Gerrit’ built and move on, that’s my motto!

What Did I Learn?

Mini quads (and even tiny micro ones as I’ve since discovered) are basically just as expensive as a large 4 or 5” ones, for the most interesting reason - that the technology in them all is the same. That is to say the flight controllers, transmitters, cameras, etc are all the same thing but in different sizes (and powers). So whether you’re building a swan of a quad or a tiny dragonfly.. the cost can be similar. It’s worth thinking real hard about what you can recycle and what you honestly need, for example do you actually need video recording, OSDs, GPS, and so forth?

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