Custom Brushed Micro

Inspired by the Tiny Whoop craze — and the fact that I got my printer working correctly — I thought it would be a good laugh to try and build a little brushed micro with a fully custom frame.

Specs

Nothing particularly fancy spec-wise. Just as much as I could grab from Banggood on the cheap.

Total price came to around £50 which is fairly decent, not including the cost of things I broke and had to buy extras of, though! It has an AUW of around ~70g which is apparently quite heavy.

Frame

My goals for the frame where to make something compact, enclosed, and as strong as I could get, while being easy to put together and take apart. I am not a huge fan of how the majority of Tiny Whoop builds have the whole top case open — doesn’t seem particularly safe for crashes!

I went through around 15-20 revisions before settling on the end version. A few pictures of the process follows.

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Printing one of the first revisions. I planned to snap the motors into place using clips but it was far too flimsy.
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Nearing towards the final design. The plan with the motors here was to slot them in from the bottom and secure them with another clip, but this was also super flimsy and awkward to print at the sizes I needed.
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Almost the final version, just lacking the circular rib.
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The complete frame!

The final frame is made up of two parts: the main body (with the motors, FC and camera mounts), and the bottom shell (with battery holder and VTX mount). The boards snap in place, and are held with a little bit of double-sided tape to stop it from popping out on crash. The motors also snap into place and are secured with zip-ties. Finally, the whole thing is zip-tied together.

Both pieces of the frame with all the components inside.
Both pieces of the frame with all the components inside.

It is printed with PLA plastic and is reasonably strong, though it is far from perfect. A lot of time was spent on getting the ribbing thick enough in the right places to stop it from flexing too much, and as a result it seems fairly crash resistant! I would like to try print it in ABS or Nylon to see if it makes it significantly stronger (and lighter as they are both less dense than PLA) but I’m yet to pick some up.

Flight Controller

The SciSky is an awesome board. It is super tiny and the built-in DSM2 RX saves a lot of hassle in trying to fit things on top of it. It spots two IO ports powered by a 5V 500mAh regulator which I ended up using to power the camera and VTX. They are connected to UART3 and I2C, one of which is in use by the RX and the other lacking in much use — so definitely most useful for the power regulator.

The SciSky board slotted in the frame.
The SciSky board slotted in the frame.

It runs the latest BetaFlight with all the bells and whistles as you would expect, capping out at 1.6 kHz gyro update and PID loop times.

I would have really appreciated a buzzer port for battery warning but it starts to drop out of the sky fairly quickly as it’s running out in any case. It is possible to fit a buzzer by soldering directly on to the chip but I’m not too keen on that just yet!

Camera & VTX

To keep things super compact and closed, I decided to grab just a VTX module and external camera. There are great AIO cameras (i.e., the ones aimed at the Tiny Whoop and other brushed quads) but the fixed antennas looked a little awkward to work around.

The video setup. The antenna is rubbish!
The video setup. The antenna is rubbish!

It is quite compact but I would probably try use an AIO camera for future builds. I didn’t have enough space to fit a DIP switch so it’s permanently locked at 5,865 MHz, and my terrible one-wire antenna doesn’t work very well beyond line of sight.

Conclusion & Video

You can see a video of it scooting about my office below. I’d say it worked out pretty well, over all! The heavy interference is probably from the WiFi access points dotted around the office, but it is more likely to be because of the rubbish antenna.

 


Extra Bits & Pieces

The SciSky has a built in DSM2 receiver so I had to pick up a TX module for so I could use it. Thankfully, there’s a nice open-source DIY multi-protocol module available that works with the Taranis, and Banggood also sells an already assembled version. It works really well and supports an absolute ton of different protocols.

Slotted into the Taranis. Comes without a case so one needs printed.
Slotted into the Taranis. It comes without a case of any kind so one needs printed.

By default, selecting a protocol and binding is done by turning the rotary pot on the back and hitting the physical button but it also supports serial comms with modded OpenTX/erSky9x firmware. Using the physical buttons is a massive pain, particularly because it only binds on power up and I got sick of hearing “WELCOME TO OPENTX!” over and over, so I swapped to this very quickly.

A quick bit of soldering and a firmware flash gives you a full host of options for the module.
A quick bit of soldering and a firmware flash gives you a full host of options for the module.

The only extra thing I would add is that it is highly recommended you flash the latest firmware on the module. The firmware version on the Banggood board is ancient and had a bunch of problems with DSM2.

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