Overview

This is my first 4 inch micro build. The frame used is steel4 from banggood (a clone of micro apex 4). Wanted a durable frame and this is the one that I could get hold of. Motors are Eco II 2004 3000kv from Emax. A Chriss Rosser video on the same made me decide on this. I had a spare caddx vista unit with dji camera and is the one used in this build as video system. The electronics - FC (Aikon f7 mini) and ESC (Diatone Mamba F30 mini) are from another 2 inch micro quad that I had (these electronics were an overkill for the 2 inch). For propellers, there are not many choices and Gemfan Hurricane 4023 is the only one that was available with a t-mount. For battery I chose Tattu Rline 1050mah 4s 95c for a longer flight time.

Build Highlights

• The frame feels sturdy and the carbon is of decent quality, however was not of the best finish. Had to chamfer the sharp edges. A small file comes bundled with the frame and that will do for the job. I dipped the frame in water while filing to avoid inhaling any of that fine carbon dust.

• The camera plate does not fit well out of the box. Required some filing to get that fitted into the top and bottom plates.
• The arms fit perfectly in the sandwiched design between two bottom plates. Once secured with screws, no wiggles and feels very sturdy.

• The screws for the standoff are of M2.5, not the standard regular M2 or M3. Care must be taken not to lose it. May not be easy to get the same specs screws.
• The FC-ESC stack required M2 screws and the M2 screws were a bit wobbly with the bottom plate. Added a silicone o-ring to get that firm in place (see the picture).

• The ESC is mounted with its battery lead and capacitor facing towards the front of the quad. This is because, when the vista unit is mounted, there is no space for the capacitor between the front and back stacks. This altered alignment required a remap of the motor resources in betaflight CLI.

• FC port is aligned properly with the ESC port for the FC-ESC connection, so no change required in the FC orientation. It stays default.
• Though the FC has a dedicated DJI quick connection port, it comes on the sides and the wires were protruding out when it was connected. It didn't feel very durable and I did not want those wires to go lose and come between the propellers in mid flight. So the quick port is not used, vista wires are directly soldered to the FC.

• FC comes with a 10V/1.5A regulator which comes very handy for DJI. Vista unit is soldered to the FC 10V pad instead of soldering directly to the battery pads (VCC). Refer wiring diagram below.
• Used foam landing pads to reduce scratches on the bottom plate during landing.
• Happy Model EP1 receiver is used with the smaller length antenna (it comes with two lengths to cater to different builds). It is wrapped in a clear heat shrink and mounted on top of the vista unit with a double sided tape. I would have preferred to wrap the Rx in kepton tape considering the heat vista unit could generate (may be for later). A cable tie is also used to secure the vista unit, the receiver and the wires together.
• Battery leads are secured to the middle standoff using a cable tie to avoid the tension on the ESC pads during battery removal (or crash).
• The capacitor is slightly bent towards the bottom and a thick double sided tape is kept between the bottom plate and the capacitor to hold it firm in place. Besides the camera comes just on top of the capacitor which avoids it from moving around and breaking the leads in the long run.
• Battery pad that comes bundled with the frame fits nicely with the cuts and edges aligned to the top plate.
• Receiver antenna is mounted on the back edge of the bottom place using a cable tie. Did not use the tpu antenna mount that came with the frame (that's suitable for a 900MHZ antenna like crossfire or R9M).

• A caddx antenna mount is used to secure the video tx antenna to the tpu part at the back of the quad. The antenna tube is thinner than the mount, so used two heat shrinks one on top of the other to increase the diameter of the tube where it is secured with the mount.

• A heat shrink (blue) is used on the vtx antenna cap to improve the durability ( i have prior experience where the antenna cap easily comes off during a crash, this technique prevents that from happening).
• The frame also comes with a gopro mount, haven't used it on this build yet.
• Motors come with 2 sets of screws for mounting - M2 6mm and 8mm. Use 8mm when the tpu arm guard is used, otherwise 6mm should do.
• The propeller T mount is secured with the screws that come with the motors (i think it is 9mm M2).
• Dry Weight : 234gm
• AUW with R-Line 1050mah 4S battery : 355gm

Wiring Diagram

Configuration:

• PID tune so far is the default betaflight 4.2 tune. Will update here when that gets changed.
• ESC is blheli_S flashed with bluejay firmware.

• Motor resources are remapped to match the current orientation of the ESC

• In the ports tab
  • UART2 is enabled for Serial Rx (HM EP1 is soldered to T2 and R2 pads)
  • UART5 is enabled for Config/MSP - T5/R5 pads are soldered to Vista unit.

• Enabled Bidirectional DShot and rpm filtering

• Rates are changed to my usual "actual" rates.

• Filters are at betaflight default. No change so far.

• On the receiver tab, mode is set to serial based receiver, and the provider is selected as CRSF. Aux12 is set as RSSI channel (used to get the rssi value on OSD).

• Enabled OSDs are - Battery Average Cell Voltage, Battery Voltage & RSSI Value

• Maximum arm angle is disabled (set to 180 deg) in the config tab.

• Display and OSDs are enabled in the features section of the configuration

• Modes tab mapping is as given below.