Building the 215 Hopper

As promised supplied here in is everything required to put a 215 Hopper together exactly as I have built it.

Please see the end of this article for an update regrading a mistake with the originally supplied brd file.

The digital assets can be found on YouMagine or Thingiverse.
There is nothing specific about the 3D printing requirements, 15-20% infill will do the job and a typical 0.2mm layer height is ok.
For the PCB’s I typically use Dirty PCB’s from Dangerous Prototypes. The brd file to submit is included with the digital assets. Options you will need to specify are 1.6mm thickness, color black (or your preference) and ’10×10 max’ for the size. Note that I have found some flexibility with this limit as this board is actually larger than 10cm in one direction, I got no questions when ordering my first batch (of which I still have 8 unused). The cost they offer can’t be beaten but do note that they are a bare bones sort of service so support is limited, what you submit is what you get.

Purchased Items

  • Naze32 Rev 6 Flight Controller (NextFPV)
  • FrSky x4r Receiver (NextFPV)
  • DYS BE1806-2300KV BE Series Set of Four CW/CCW Motors (NextFPV)
  • 4x ZTW Spider Series 18A Opto Lite (NextFPV) This could be considered overkill from a power point of view, I chose it for its svelte size and preloaded blheli.
  • MultiStar Racer Series 1400mAh 3S 40-80C LiPo (Hobby King) I usually start with 3 of a particular battery size but the more you get the more you can fly.
  • 5×4 Propellers (NextFPV) I like to use a bright colour (usually orange or green) on the front and black on the rear to help with orientation. 4 propellers are required, 2 CW and 2 CCW, but buy plenty of spares.
  • 500mm x 12mm x 10mm carbon tube (ebay) Cut in to two pieces, both 183mm long, there will be a short piece left over.
  • 5V, 500mA Step-Down Voltage Regulator D24V5F5 (Pololu)
  • 20x M3x8mm hex socket button head screw (ebay)
  • 8x M2x16mm torx socket screws (ebay) A generic M2x16 cap or button head will also work however for anything smaller than an M3 I find that a torx socket is more reliable than a hex.
  • 8x M2 Washers (ebay)
  • 8x M3 nylon nuts (ebay)
  • 8 M3x15mm nylon screws (ebay)
  • 10x 15mm round threaded standoffs (ebay)
  • Battery strap (Hobby King)
  • 16 AWG silicone wire (Black Hobby King, Red Hobby King) This size wire is the largest size that will fit through the wire slot on the power distribution board. It is also the same size as the leads on the battery.
  • XT60 male connector (Hobby King)
  • XT60 female connector (Hobby King) Purchase 1 for every battery. I managed to fuse the XT30 connector together, admittedly whilst running 5 motors on a heavier rig, however I think the upgrade is still a worthwhile precaution.
  • 2x JST-PH pre-wired plugs with sockets (ebay) for Vbatt and 5v connections on power distribution PCB.
  • Self adhesive rubber feet 25mm(L) x 5mm(W) x 3mm(H) (Aliexpress) These seem a very uncommon size but are available if you are prepared to wait for delivery. Alternatively anything that is 3mm thick can be used as a spacer. They are required as the battery wire penetrates the top plate below the battery.
  • 9x 160mm x 2.5mm cable ties (Hobby King)
  • 20mm heat shrink tubing (Hobby King) for the modified receiver
  • 10mm heat shrink tubing (Hobby King) for the modified ESC’s
  • 1x 1 pin crimp connector housing (Pololu) For SBus connector to Naze32
  • 3x 2 pin crimp connector housing (Pololu) For receiver power, SmartPort and Vbatt at Naze32.
  • 2x 3 pin crimp connector housing (Pololu) for receiver connection and 5v connection to Naze32.
  • 13x Female crimp pins (Pololu)

Note that a lot of the links provide, particularly for small parts, direct you to sources that are sold in bulk lots. For example the M3x8mm hex socket button head screw I have linked are sold in a lot of 100. As you only need 20 do not purchase 20 of the linked item, 1 bag will give you enough to build 5 215 Hoppers.

Custom Parts

  • 1x Left side pannel (215H 103)
    215H 103
  • 4x Motor mount bottom (215H 104)
    215H 104
  • 4x Motor mount top (215H 105)
    215H 105
  • 4x Tube clamps (215H 108)
    215H 108
  • 1x Right side pannel (215H 111)
    215H 111
  • PCB

Optional Parts

  • 1x GoPro session mount (215H 113)
    215H 113

Build Notes

This is not an exhaustive step by step for building the 215 Hopper but rather a collection of build notes in the basic order of construction.

  1. 3D printed holes for fasteners should be drilled out to their finished size after printing. This includes the 5mm holes for the frame standoffs (parts 103, 108 and 111) and the 2mm holes in the motor mounts (parts 104 and 105).
  2. Depending on the quality and accuracy of your prints you may also need to clean up the counter bore for the head of the M2 fasteners. This detail can be particularly critical as there is very little thread engagement in the motors and getting the thread started can be challenging. If you are using a hand drill for this process take it very slowly and carefully. It is easy for the drill to bite and get pulled in too far. Grinding a flat point on to a spare drill bit can minimize this biting problem.
  3. The PCB needs to be split in to its two pieces along the tabs. Side cutters and a file will quickly tidy up any leftover material. Also round over any sharp edges where wires, zip ties and the battery strap rest.
  4. Clean up any edges on you 3D prints the prevent the parts fitting together nicely. Likely areas that can cause problems in this regard are the knobs that fit into the slots on the PCB’s and the wedge between the side panels and tube clamps. The holes in the side panels should be a loose fit around the tubes.
  5. Solder the 5v regulator and JST sockets in place on the power distribution board.
  6. Shorten the signal/ground connectors from the ESC’s. I found if left as they are supplied there is simply too much bulk in the tight confines of the 215 Hopper.
  7. Solder the motor wires directly to the ESC’s. This will mean that the wires must first be threaded through the last window in each end of the side plate. As previously mentioned this is a bit awkward and one of the shortcomings of the design. You will want to have a rough layout with arms and motor mounts in place to determine the length of wire required.
  8. Once the two previous adjustments have been made to the ESC’s reseal them with heat shrink tubing before cutting the input connections short and soldering them directly to the pads adjacent to the mounting points. Ensure you have the ESC up the correct way to match +ve and -ve connections. The ECS’s can be secured in place with zip ties. As there is no support for the signal wires a dab of hot glue will prevent them moving and possibly breaking.
  9. Solder 16 AWG wires on to each battery terminal and route the wire out through the rear slot. Trim the wires such that there is about 10-15mm of overhang past the end of the board. Attach the XT60 male connector to the end being careful with polarity. You may wish to position a battery to determine exactly how long you would like the battery connector to be.
  10. Prepare the SBus and SmartPort interconnects. The SBus interconnect should have a 3 pin connector at the receiver end. At the Naze32 end, 5v and GND should be on a 2 pin connector with the signal wire on its own 1 pin connector. The SmartPort interconnect need only connect the signal wire to both pins of a 2 pin connector. Use the breakout wire supplied with the X4r, remove excess wires and add a short loop between the two pins.
  11. Prepare the Vbatt and 5v interconnects. The Vbatt interconnect (pictured at top) should have a JST-PH connector on one end and a 2 pin connector at the other. The 5v interconnect (pictured at bottom) should have a JST-PH connector at one end. At the other end either a 3 pin or a 2 pin connector will work, on the Naze32 I connect it to motor port 5. Double and triple check voltages and polarity are correct before plugging either of these in to the flight controller. I damaged a receiver because on the initial board revision polarity of the 5v was reversed at the JST socket. This has been corrected on the supplied board layout.
  12. Use the nylon fasteners to attach the flight controller to the appropriately marked PCB. Each screw comes through from the outside and is secured to the plate with a nut. The Naze32 is then stacked on top and secured with another screw. Prior to attaching it to the PCB install pins on the Naze32 rev 6 as follows:
    • Motor ports – 90° header on top side and pointing away from centre.
    • Digital ports – 90° header on bottom side and pointing towards centre.
    • Auxiliary ports – 90° header on top side and pointing towards centre. This header will also need to be a little higher than usual to clear components on the board. The easiest way to achieve this is to attach a connector before positioning the header strip.
  13. Positioning of connectors dictates that the x4r must be modified to fit correctly. For me this is not a concern as I only use SBus and usually dedicate a receiver to each model. After removing the cardboard housing trim to remove the top row of servo connectors (i.e. the row which SBus is NOT on). Snip the wires before the plastic so that the plastic can give whilst you are cutting it, this will prevent splitting through the bottom row. The remaining connectors may need to be bent down slightly to dip under the ESC connectors on the flight controller. Once modified seal the receiver with heat shrink, you may need to cut a small window for the Smart Port connector. Zip tie it in place on the same board as the flight controller.
  14. It is easiest to assemble the frame upside down. The power distribution board is the top panel, the receiver and Naze32 are on the inside of the bottom pannel.
    Put the battery strap in place around the power distribution board
    Push the standoffs in to their holes and loosely fasten them to the power distribution board with screws. Put the arms roughly in place, the friction on the standoffs should be enough to keep everything in place.
  15. I found the easiest way to get the motor mounts on to the tube was to first screw the two pieces on to the bottom of the motor (do not tighten but ensure there is a couple of turns of thread engaged) before sliding the clamp on to the end of the tube.
  16. Connect the ESC’s, 5v and Vbatt to the flight controller then roll the bottom board over on to the bottom of the frame, poke the antennae out a couple of the side windows whilst tucking all the wires into the frame.
  17. When closing up the body be careful that no wires are pinched between the side panels and the PCB’s. Before locking everything down ensure that the arms are centered (measure from the side of the PCB to the inside of the motor mount) and that the motors are vertical. Rather than simply eye balling this put your propellers on and ensure the tips meet at the same level. Remove your propellers before connecting any power.
  18. Position 4 sticky feet around the battery wire penetration slot and battery strap to support the battery.

215H2-2

Configuration

My flight control software of choice is CleanFlight. When you first connect to CleanFlight there will be a number of setup changes to make. As a starting point change the following:

  • Enable Serial RX on UART2
  • Receiver Mode RX_SERIAL
  • Serial Receiver Provider SBUS
  • ESC/Motor Features Enable ONESHOT125
  • Minimum Throttle 1040
  • Maximum Throttle 1900
  • Battery Voltage Enable VBAT
  • Other Features Enable SOFTSERIAL and TELEMETRY
  • Enable SmartPort and SOFTSERIAL1.

On the PID Tuning tab:

  • PID Controller MultiWii (I found that the Naze32 was struggling with LuxFloat whilst SoftSerial was enabled)
  • ROLL rate 0.4
  • PITCH rate 0.4
  • YAW rate 0.52

Setup auxiliary switches on the Modes tab as you would like. I typically assign a switch to ARM and a 3 position switch to ANGLE/HORIZON/RATE.

You will then need to connect a battery (no propellers attached!) to ensure everything on the receiver tab is coming through correctly.

From here all the usual maiden flight checks and safety procedures apply.

If you have any questions about the build or would like more images or information about something specific feel free to leave a comment here, visit the contact page or leave a comment on either the YouMagine or Thingiverse pages.

If you build a 215 Hopper I would love to see the results. I have set up a form where you can tell me how it went and let me know where I can find some photos of your work.
Build Form

Update 1:
It has been brought to my attention that the original brd file that I upload had a fault on the vbat connector. The ground trace from said connector did not reach the main ground plane. Now uploaded is revision 2 of the board with this problem corrected.
My apologies to anyone who has already made the board. You will still be able to fly with it but you will need to forgo the connector for vbat and connect wires directly to the same pads as the battery leads (mind the polarity), or leave them off all together (mind you don’t over discharge your batteries). I have ordered a new batch myself so if anyone has already made boards and would like a corrected replacement get in touch.

215 Hopper – Build 2

215H2-2

I have been a bit slow in getting this report together but I am pleased to say the as of late last sunday evening my second build of the 215 hopper design is airborne. For anyone keeping track that is just a 6 day turnaround from lost to flying again. There are a couple of things that worked in my favour to achieve this.

  1. Firstly the 3D printer from the workshop of SteelCity Electronics is currently on holiday to my workbench, as such I was able to start printing replacement parts immediately (more on this topic in the near future, I’ve got a big build cooking).
  2. The guys over at NextFPV actually had stock of every replacement part I needed. I expected I would need to order various bits from multiple sources internationally but discovering everything was stocked locally was a pleasant surprise. On top of that the service they offer is exceptionally fast. I am a very happy repeat customer of theirs. I the future I will gladly purchase through them whenever possible (hopefully there is an FPV setup in my future).
  3. When ordering parts for the first build I doubled (or more) quantities of the various bits of hardware so all of that was on hand. The PCBs were taken care of as DirtyPCB’s supply 10 per order by default.

With the rebuild I got the chance to address a few of the shortfalls of the first build. Changes included:

  • Shortening ESC signal/ground wires so that there was less wire bulk in the body. it was a bit challenging squeezing everything in to the first build.
  • Direct connection of motors to ESC’s. On the first build I needed to join the motor wires with the ESC wires as the motor wires were cut to short from the Spidex 220 build. In reality this is still not a very practical solution as the wires first need to be passed through the side plates. However for the sake of minimalism I stuck with it.
  • Externally accessible USB. This is the most valuable change from the first build and is thanks mostly to the change in location of the port on the Naze32 Rev. 6 board. I also printed a unique side plate with an opening to suit.215H2-3
  • The upgrade to the Nae32 Rev. 6 also allowed for very tidy connections all around (no more soldering wires directly to the board). Seen in the photo below is the way I have installed the pin headers on the Naze32. 90° headers are used on all connections. The ESC outputs are installed in a fairly typical configuration. The RC input connections are under and towards the centre of the board and the extra features (Vbatt, buzz etc.) are directed back across the board.215H2-4
  • SmartPort telemetry. Rather than trying to fit a buzzer inside (which becomes surprisingly large in such a small space) I connected the SmartPort on the X4R-SB to a soft serial port on the Naze32. A buzzer will fit inside but for now I am relying on the telemetry to know the status of my battery. The photo below shows how tidy this setup is. Also note that for clearance to the ESC connections on the Naze32 I have to trim the top row of headers from the X4R-SB.215H2-1

The only quirk with this build, and I find it strange given that it is newer hardware, is that LuxFloat can’t run reliably ( I had no problems with it on Rev. 5 hardware). It may in fact be the extra processing load from the soft serial so I will have to check into that further.

Next on my agenda for this copter is to get the GoPro mount(s) sorted. Then put together a more thorough look at the design and build process with a full bill of materials and files if you would like to build you own.

Given that the design of the 215 Hopper was inspired by the FliteTest VersaCopter I thought a family photo was a fitting way to end this post.

215H2-5

Flite Test VersaCopter

I’ve been on the lookout for a small quadcopter kit to put together for some time with an ultimate interest in getting in to FPV flying and racing. The high entry cost for a good quality full FPV setup has put me off a number of appealing options over the last 12-18 months such as the ImmersionRC Vortex. I have however finally pulled the trigger on the VersaCopter created by the crew over at Flite Test. This will allow me to put together a rig piece by piece and offers a compelling value proposition. A couple of days ago my kit arrived so over the weekend I have assembled and flow my VersaCopter.

Shopping

VC-1

Delivered from the Flite Test store (as shown above) was:

VC-2

Delivered from the HobbyKing strore (as shown above) was:

The only missing piece from this shopping list to get off the ground is a radio receiver to suit, in my case, a Taranis X9D. I already had a couple of FrSky X4RSB‘s on hand from a previous order.

Assembly

One of the reasons I was so eager to jump on this kit was the design style used. The slot together laser cut plates really appeals to my sensibilities and I was curious for a close up look at what laser cut Delrin looked like and offered structurally. I have used similar construction methods in the past for other projects but have always used acrylic (unfortunately Ponoko NZ, whom I usually use, do not offer a Derlin option).

VC-3

Assembling the VersaCopter from the kit as shown above followed almost exactly as demonstrated in the Flite Test construction videos (both the main video and the NAZE 32 video) with the exclusion of any cameras or FPV equipment and the observations as follows:

  • When installing the motor mounts on to the arm I found it easiest to start only the bolt on the side opposite the slot. This allowed full freedom for the Delrin part to stretch over the tube before adding the 2nd bolt.
  • Aligning the motors on opposite ends of each arm proved more challenging than ensuring the front and rear motors were aligned. I didn’t come up with any clever solution to this beyond align, tighten, check, repeat.
  • The supplied ESC’s seemed to include a much larger input smoothing capacitor which made their length significantly longer. This provided two problems for the installation of the NAZE 32:
    • The wires and capacitor interfere with access to the USB port through the side window.
    • The length meant it was particularly tight trying to fit the ESC between the NAZE and the rear arm, consequently the ESC is in constant contact with the edge of the NAZE board somewhat nullifying the foam isolation mounting of the flight controller.

    Ultimately the compromise was to push the ESC as far back as possible and hold the input wires down as best as possible with an extra cable tie.

  • With about 4-5mm of foam under the NAZE 32 there is not sufficient vertical space within the frame for vertical connectors. This impacts the telemetry, vBatt, buzz and serial ports. Directly wiring JST tails to those I wish to use will be required.
  • As I am using the SBus output from the receiver I had to set serial port 2 on the NAZE 32 to serialRX. I overlooked this detail and spent some time trying to figure out why I was not receiving a signal.
  • I was not happy with how secure the battery felt with just the velcro strap as such I added some Velcro dots to the top of the frame and bottom of the batteries for extra security.

Ultimately the kit went together very well and they have certainly delivered on their aim of putting together a DIY kit that looks professional and tidy when completed.

VC-4

Flying

After running through 6 batteries I can say that I am very happy with the VersaCopter and it delivers all that I had hoped. Specifically a no nonsense quad with decent flying performance, i.e. something that will allow me to practice flying with minimum fuss.

The VersaCopter was stable without making any changes to the PID tuning however for better performance I have made a few initial tweaks. The following settings have changed:

PID Controller: 2 – LuxFloat (all default PID values)
Roll rate: 0.05
Pitch rate: 0.05
Yaw rate: 0.17

On the transmitter I have set:

Roll +25 exponential (faster closer to centre)
Yaw -35 exponential (slower closer to centre)

With this setup flight times of between 7.5 – 8 minutes are easily possible with relatively energetic flying (constantly on the move, regularly at full throttle, flying square or figure 8 circuits) and approximately 10-15% left in the battery.

So far I can not report on the durability of the frame, I haven’t crashed it yet.

MultiChase Project

As a foot note there are a couple of lessons to be taken from this build for my MultiChase project.
Wiring, routing and position of electronics needs to be very serious consideration, wires are not as flexible as imagined in close quarters and all connectors and wire volume needs to be accounted for. I already knew this but this project served to reinforce that knowledge
With a 6″ propellor the difference between a 250mm and 280mm motor centre is probably fairly minor.
The laser cut plates method of construction proved very simple to put together and supported by the fibreglass plates provides a very strong frame, it is probably worth reconsidering for as an option.
Delrin looks to be a great material in this laser cut form, tough but still somewhat flexible. I will however continue with my 3D printing approach for now as that is easily available to me.

Power and Control

This update is only a small one with the inclusion of the flight control board (blue) and the motor speed controllers (purple). Positioning of the speed controllers is very temporary. I would like to investigate mounting them directly to a power distribution board to reduce wiring. As the layout develops so will my thoughts about what form this board may take.

Given this is looking more and more crowded I also looked at what impact increasing the motor spacing has. Currently, and in all pictures to date, the motor axis are on a 250 mm pitch circle. Increasing this to 280 mm increase space quite dramatically however I feel it is to premature at this point to be increasing the size without determining that this smaller size can’t be made to work.

I have also be wondering on the sense of my idea to use a boom for the rear motor. The popular plate based design holds appeal for ease of assembly and layout however I tend to design within the constraints of fabrication techniques easily available to myself and currently that is 3D printed ‘connectors’ and off the shelf sections.

Components added are:
Flight controller: Naze 32 “Full” Flight Controller (the “Acro” version would also be suitable)
Speed controls: Afro ESC 12Amp

MC2 004