Cheap 3" Drone for taking HD video

Ever since the intern Canadian UAV regulations were released, I've been wanting to put together a relatively cheap, but HD Camera carrying drone that is light enough to be exempt from any regulation. At the threshold of 250 grams, it was actually quite doable at a relatively low price given the extremely rapid developments in the DIY quadcopter industry over the past few years.

This is the second, but much more used iteration of the particular frame. The first had a 4 in 1 ESC and F4 controller which I blew up on a hard crash (did not disarm when it dove into the ground in acro mode), and due to parts I had available it was rebuilt using slightly less optimal (weight-wise) parts but ended up flying very well, so I kept it even after replacement parts arrived.

Before delving into the details, here's a google photos-created video from some footage I took while travelling in Finland for a conference. The small size of the quad means I can carry it easily in a backpack containing my work laptop (13" MBP) without adding too much extra weight.

Here's the finished build "in action" next to the transmitter, out on the field on Aalto University campus:

Parts list and build details

Frame: Realacc RX130 that came with a Matek PDB. (Used to be able to find it for about $13-15 on Aliexpress)

Motors: ReadyToSky 1306, 3100kV (available only on AliExpress from what I can find; example link. They are super cheap clones of the DYS 1306 at half the price, but the latter are much better in quality. Supposedly 4s capable but I've only ran them on 3s so far. Works fine!

ESCs: EMax 12A "BlHeli" which actually had to be manually programmed with "real" BlHeli. They're not super light but can be found for cheaper from eBay and AliExpress merchants. However, I would actually rebuild it with a BS412 (25x25mm) or maybe a RacerStar 4in1 (30.5x30.5mm). The latter is 20A and would work with 1407 motors which could support a larger craft (160mm frame swinging 4" props). A 4in1 (even larger 20A one) would also be considerably lighter than the 12A EMax's I'm using. For discrete ESCs the EMax Bullet series may be better as they're much smaller and lighter.

FC: I'm using a strange Piko BLX clone board that has a curious 23mm!? hole spacing. It fits in between the standoffs of the 30.5mm spaced stack, but is not ideal. I would probably just go with a full size 30.5mm FC for this frame next time... or else go 20x20.

Receiver: FlySky A8S. Tiny, supports failsafe fine despite product description stating otherwise, and no reliability issues that seem to be a problem with older versions that are no longer sold on BG...

Batteries: ZOP power 3s 500mAh 45C. They're not rated for consistency, and of the two I have one seem to work better than the other. Having said that both allow me to zoom around for about 3 minutes or so lugging the HD camera, or do more aggressive manoeuvres without the camera.

Props: DYS 3045. The only 3" props I've used so far. Seems to be a good match and they're pretty, so not too much to write about at this point... ;)

Camera: the trusty RunCam 2 HD. Weighing in at 50 grams with battery and SD card, its not the lightest option but its a nice action camera to boot. I could have shaved about 15 grams off by not using the battery and powering it off the 5V rail of the PDB instead. Another interesting option would be the new Split that weighs about 20 grams or so and has a faster analog signal for realtime FPV feed (requiring an analog transmitter of course), but the Split is pretty much a dedicated flight camera and can't be used elsewhere by itself.

Transmitter: The trusty FlySky i6 which I modded to 10ch, and the i6ab receiver is still working well on the 250 class quad.

The build weighs in at exactly 250 grams with the camera, which is about 15 grams more than when I had the BS412 4in1 ESC and F4 controller with built in 5V regulator which eliminated the need for a PDB. This means I don't have room for a lipo voltage checker/alarm (such as this one), and I have to go by gut feeling and go by experience from more open locations when I didn't need to conform to regulation.

Previously, with the lighter 4in1 ESC:

Here's some raw, unedited zooming-around-the-park footage:

All in all, a very fun quad that gets a lot more action than the 250 (5") one due to the size and legal status. The Canadian regulations have recently been updated to be a lot more reasonable, but anything that weighs over 250 grams (and less than 1kg) is still relatively restrictive in terms of space.

Cheapest Brushed Tricopter Ever? [Detailed Part 1]

[disclosure: some of the banggood links contain an affiliate code, but many products are discontinued or outdated so consider seeking current alternatives!] 

What started off as a mental exercise turned into an actual implementation of not the first, but perhaps cheapest possible brushed tricopter in existence that I'm aware of. An overview of the list of parts and some sample flights are available in this previous post.

Quick Intro

Before starting, there are some existing work including this one which basically describes the entire idea, but requires a very well made yet somewhat $$ Multiflite Pico flight controller. Since this was purely a casual exercise and I've already spent a hefty budget on larger brushless builds, I wanted to keep it as cheap as possible.

Main Challenges of a brushed Tricopter

The concept of a tricopter is relatively simple: instead of pairs matching counter-rotating in a quad (2 pairs laid out on the same plane), a Y-copter (2 side by side and 2 overlapping at the tail), hex (3 pairs, single plane), Y3 (3 pairs overlapping), Octo (4 pairs), etc... Instead, a tricopter has an odd number of rotors, which means that the yaw cannot be controlled via rotation of the driving propellers alone. In order for yaw compensation, a tail servo allows the third motor to tilt, providing the counter-rotating forces necessary to keep the craft pointing the same direction while having independent control of the overall throttle.

Both BetaFlight and CleanFlight have tricopter modes, and in these modes, the first two channels become servo controls while the remaining channels (3-6) become motor driving outputs. However, with brushless boards, normally only brushed motors are expected as outputs and so the PWM outputs are usually attached to the gate of a driving mosfet through a resistor, which then switches the motor pads between V+ and GND. This means that one would not be able to, out of the box, add any servo to these boards.

There are two main issues here:

First, I would need to bypass the MOSFET motor output of the servo channel for the tail. This would involve finding a spot on the PCB to solder an extra wire to.

Second, I would need to move the motors to channels 3, 4, 5. Here's where another issues arises: most brushed FC's that physically support only 4 motors are hardwired to channels 1-4, which means there are only mosfet drivers and motor pin pads for those channels. The reassignment in tricopter configuration would result in channels 3, 4, 5 being used, and channel 5 would not have any driving circuitry. While it would be possible to hack the FC code (BF or CF) to move the servo assignment to, say, ch 5 or 6 and retain the motor driving hardware, there is a further issue since on the PCBs, the latter channels are completely unused (not soldered to anything), and would require direct soldering of a fine wire to the tiny pins on the QFP microcontroller package itself- not a feat for the faint of heart!

*edit*: a helpful redditor mentioned that in BetaFlight the resource mapping function could potentially solve some of these issues without recompiling the FC code. It doesn't quite solve the problem of potentially having to solder directly onto the microcontroller package, but its a start! May be worth trying out as there are a number of cheap F3 brushed controllers out there that only have 4 motor drivers...

The Multiflite Pico is the only brushed FC I'm aware of that explicitly exposes servo output on a pad, which makes building a tri possible. However, it is also out of budget for this project. (And if you've ever flown a brushless mini-quad of *any* size, you probably don't want to invest any significant amount of cash into any brushed build these days... but I digress.)

The Solution

As luck would have it, the Eachine Naze32 brushed board (many clones under "HappyModel" and "Realacc" exist from various other retailers, and in fact the "Eachine" branded one actually came with Realacc markings on the bottom... ;) is a hex-capable brushed flight controller that I also had an extra of on hand from the popsicle quad build. This means that there are additional mosfet channels available, so even after the servo assignment to CH1 and 2, it would still be possible to use motor channels 3-5. The next step is to find exactly where the CH1 motor output is. For that, I dug up the naze32 schematic along with the datasheet of the STM32F microcontroller. Following (red rectangles in the image below) show the pin we're interested in:

What you see on the actual board is one pin of a SMD resistor that connects between the microcontroller's PA8 pin (29 on package), and the gate of the MOSFET for motor 1. After checking with a multimeter and confirming those two are indeed the same point, I proceeded to solder a wire onto that pad which should in theory provide the PWM servo output. (It might not look that difference in size, but its MUCH easier to solder onto that SMD pad than the leg of the microcontroller itself - not only is it considerably larger, but perhaps more importantly, there are no other pins nearby!). It was also a good time to test out the fine tip of my new super cheap (but working well so far) iron. Here's what it looks like:

The white cable is the signal, while brown (5V) and black (GND) make up the rest of the servo connections. Since the micro-servos I plan on using is super low power, using the 5V regulator of the board is OK. However, looking back it would have probably been better to use VBatt directly (unless I plan to use this board in 2-cell mode with more powerful motors... more on that later). Since the white cable is just connected to the resistor pad, adding a dab of super glue under the white cable prevents it from ripping off.

Next up is to test that it works:

And it does!!!

Second part of the build log TBA...

Popsicle Quad, V2

So after the first version, made with HaagenDaz sticks flew a bit, I wanted to make some upgrades. Specifically, I wanted a.)more power and b.) a bit more clearance to mount an AIO FPV (all-in-one first-person-view) camera, such as the TX02 that I had on hand. To do so, alas, would require a slightly larger frame. So I picked up a bunch of "craft grade" popsicle sticks (there's only so much sugar we can handle) from the dollar store, and got to designing a new frame.

I wanted to keep on using the rubber grommets as before, which were quite good at holding the motors. The final design I came up with the following: (series of relatively self-explanatory photos)

The end result, with the old Eachine triblades:

The new props, based on the suggestion of a redditor, are the 55mm ladybird props. I also tried some hubsan x4 props which were also an improvement, but only had a set and broke them quickly testing indoors ;) I see some newer KingKong 55mm and 65mm props, which might also be good to try out. They are also a bit cheaper at $5usd for 10 pairs instead of ~$8 for 8!! The main thing is to use props with 1mm shaft holes, and to ensure there's enough clearance of course!

Looks like the props are about half a gram heavier each. The extra thrust however, was totally worth it. It's actually a bit hard to fly indoors without a prop guard, so I waited a while before good weather and opportunity arose. Here's a flight in a park taken with a run cam 2 (sorry for slanted camera placement... it's a bit hard to tell sometimes ;)

Unfortunately, I haven't had time to do any FPV flights with it, and my ghetto FPV system (to be described at some point) is quite clunky. The camera adds 10 lbs 5 grams, which is about 10% the total weight of the quad. Being 200mW it also draws about 400mW, which is not negligible for such small flight batteries. A 25mW (such as the TX01 or the switchable power TX03) transmitter would be more appropriate for this build.

HäagenQuad Micro: a tiny quadcopter based on an ice cream stick frame

Since the weather is pretty unforgiving here in the wintertime, I wanted to build a small indoor micro-sized quadcopter but still keep the control systems that are present in the larger racing/acro machines.

Originally wanting to use a 3D printed frame for this build, but after having calibration and belt wear on the Y axis, I ended up with something a bit different while the replacement parts for the printer are yet to be installed. This attempt to use popsicle sticks for a quad frame is by no means the first, but unlike that example I'm using separate "DIY" quadcopter components (typically found on Eachine QX-series for those who want to just get a complete kit with all the parts). The advantage is you get a fully configurable flight controller that can run Beta/FleanFlight, but the tradeoff is you need an actual transmitter which increases the cost. I'm using the FlySky i6.


Everything is available from Banggood. For Canada I've found that using the registered + insured option gets the shipment faster, and may help alleviate issues as experienced by many. (For other Chinese retailers, the ePacket option is great as well)

Here's a complete list of parts along with their product links. (Prices may fluctuate due to sales etc). Note they are affiliate links which mean while its the same price as if you went on the site normally, purchases generate a very small commission for me. First time trying this feature out...

Motors/props ($11.25 USD): Eachine 820 Motor (4x) + Props kit (2 sets)

I'm guessing they're similar to the ChaoLi motors. They come in CW (red+ blue-) and CCW (white+ black+) wiring. While they might spin when polarity is reversed, from what I understand the brushes may wear out much more quickly so its best to make sure they're hooked up correctly!

If I was to order again, I might try the RacerStar ones, which may be better (or simply better looking with the nice red paint scheme... red means faster, right?? ;))

Flight Controller  ($7.05 USD): Eachine Naze32 Brushed Controller

In the racing multicopter community the Naze32 is starting to show its age, and F3/F4/F?? controllers with faster processors are starting to become the standard. While the latter are available for brushed builds, it's not really necessary for a small project like this. However, I've noticed that at least F3 based ones are only a few bucks more, so if I was to make another one, I'd probably go with those. One other option would be to go with a built in receiver, such as this one for FlySky, which would make the wiring and mounting a lot cleaner! The tradeoff of course is you won't be able to use the receiver by itself for another project... Similar options exist for DSM and FrSky

Receiver ($10 USD): DasMikro Ultra Mini

Select "Type B", which has the PPM out and makes wiring super easy. Also supports 8CH with a modded Flysky i6, so you can add extra switches and knobs if you like to additional AUX channels!


Rubber Grommets for motor mounting ($1.60 USD): 20 pack 

Make sure you select the 8mm version. Outer diameter is about 10mm, not counting the lips that stick out a bit further. 10mm an important dimension as that should be the size of the hole on the arms.

JST/losi Connectors:

Instead of the losi battery connector that came with the FC, I went with the 2.54 JST since I had a bunch of those lying around.

Others:

- 2x Häagen-Dazs ice cream sticks (other popsicle sticks may work, if the ends are wider than 10mm)

- Elastic Bands

- Bits of paper etc to stick under the FC to make it level with the frame, if needed

Build Process

The trickiest part of the build, for someone not familiar with woodworking is getting the right sized hole on the arms. At first I was ambitious and wanted to drill an enclosed hole, but quickly found out that it is very difficult to do so with a regular power drill. It turns out for delicate wood like this the best way to cut through is either with a small knife, or a really high RPM grinding tool (e.g. Dremel, etc) with the right attachment. Also in the end I found out that it's OK for the outside to be open as the grommet will still sit snugly in the opening, as follows:

The first thing I wired up was the FC to the radio. Since we're using PPM, we only need a single signal wire, as follows:

Then, we just have to connect up the motors to each channel. I soldered directly onto the FC, and the only thing you have to make sure is the right motor direction. For CleanFlight, the directions are:

So motors 1 and 4 are CW, while 2 and 3 are CCW. The Red+/Blue- wired motors are CW, while the White+/Black- are CCW, respectively. So we just have to solder each motor to the correct pins on the FC:

I skipped a few photos along the way, but here's what it looks like all hooked up:

The battery get strapped in underneath, using the same elastic that holds the FC in place. Not the most secure mount, but it works!

Here's the AUW of everything:

At almost 50 grams, it is interesting to see that there are many brushless builds these days that are around similar weight. Exciting times we live in! Anyway... how does it fly?

Turns out, not very well! After some discussion online, people have recommended me to move away from the triblade props that come with the eachine motors. While they are super quiet, there isn't a lot of power. I have some ladybird props on the way which should make a difference. Stay tuned!

Here's an updated outdoor video using the new ladybirds. As you can see it actually manages to get off the ground (and clips a tree at one point and still recovers...)

Other Potential Changes

I haven't decided if I should switch everything to losi since they're much easier to plug/unplug compared to JST. On the other hand I have 5 batteries with JST already and it would take quite a bit of soldering to change them...

Finally, a family pic with a WlToys V222 (showing its age compared to modern toy quad options, but still a great intro to quadcopters), and the perpetually in-progress QAV250:

Bonus Peek:

Here's the next version, with larger and more powerful props (hubsan x4 shown, but also have ladyprops which feel even better), as well as an AIO video tx: