Le FPV250 Ghost

Since it's winter and dark outside I've been looking at LEDs for my quads. This is something that I've tried once before with great disappointment as you barely can make out most LEDs during sunny summer days. And those are the days that I actually fly.

The FPV250 Ghost from HobbyKing is actually a Diatone frame with the same name, which should come as no surprise at this point. Now, it turned up at just the right time and I ordered one. Since then, and before I started this build, a v4 of the frame has also been released with more LEDs.

Parts


The Build

Motors and ESCs

In my quest for finding cheap and appropriate ESCs I've picked a different one than the ones in the last build. The last ones had their motor wires soldered in the middle of which I thought was impractical. Well, these ones are soldered at the edges, but the solder points are covered by the heat sink (heat sink?) and wow aren't the ESCs big for a 10A 3S ESC. Removing the heat sink is not that much of a problem and while doing so you will also discover that it's probably not in contact with all the FETs anyway.

ESC heatsink. You can clearly see that not all FET has made contact with it.

ESC, a big one. You can see the huge solder balls on the power supply
that prevents the heat sink from touching all FETs.

Since the main problem with the heat sink coming in contact properly was the soldering of the power leads I resoldered them. At the same time I replaced the 18AWG lead with a 20AWG (rated 11A, will peak at 5A).

I chose to use the H1806 motors from MyRcMart for this build. Previous builds have been based on the RCX/ZMR 1804 and 1806 and they have not let me down. MyRcMart claimes that the new H1806 are of better quality than the previous ones. Only from visual inspection they do in fact look better. At least the quality seems more even and the winding is much prettier. How they perform, we'll see later.

The motors comes with long leads of soft silicon wire. They can be cut to length without any issues with enamel. I removed the motor leads from the ESCs and soldered the motor leads directly to the ESCs.

Motors soldered to the ESCs

To get the rotation direction right I simply solder two of the ESCs straight on and cross two of the leads for the remaining two. Afterwards I hook the motors up to a power source and a servo tester (or a receiver) to check which way one of the motors is spinning. After that, I know how the rest will spin as well. To avoid later surprises I always test all the ESCs and motors at this point.


Power distribution and LEDs

This frame comes with a power distribution board with built-in 5V BEC and four PCBs with LEDs, one for each arm. There should two PCBs with LEDs of the same color, but I got the wrong ones and got three green and one red. HobbyKing has promised to send me a new frame.


Testing the PDB with the LEDs.

The PDB fits perfectly in the center of the frame. The new frame has four new mounting holes to mount a mini size flight controller in the center. Unfortunately they didn't add holes that fit the PDB. I fixed it with a drill bit and a knife. I attach the PDB with nylon spacers. Later on, I also installed a variometer under the PDB to avoid most of the propeller turbulence.

PDB installed in the frame

Once the PDB is in place the motors must be mounted as the LED boards are attached with the same screws as the motor mounts. I put the ESC in place on the arm and slide over a piece of transparent heat shrink tube to attach them later. When everything seems well in place I attach the motor mounts. The ESCs can be soldered onto the PDB while installed. But care should be taken considering heat. If the PDB gets heated too much the nylon screws can melt. This can break them or melt them together and prevent them from ever coming apart.


ESCs, motors, PDB and LED boards installed and soldered.

Flight controller

Having tried the CC3D on my first mini quad I see no reason to use anything else for a pure flying machine. To get some more drone-like capabilities I would use a revo board or a APM instead but for flight experience I think the CC3D is the best. The CC3D I installed comes from a previous machine that was decommissioned.

Since I have collected a few flight controller mounts previously I tried using them on this build. First off was a more complicated version with dampers. It look really small and adapts the larger PDB base to a CC3D in a perfect way. However, with the nylon spacers below, the dampers and the nylon spacers above it build too much height and the controller board comes too high and close to the top of the center cage I will put on the frame later on. So instead I went with one of the more simpler kind of mounts.

CC3D on the flight controller mount.

To attach the flight controller to the mount you should use M2.5 nylon screws of length 12mm or more. I didn't have that. Instead I cut down the small spacers to be able to use a 10mm screw instead. I used some foam to, in a rather ugly way, add some damping between the screws and the flight controller.

The CC3D won't fit the normal way on this mount. It will fit but you won't be able to insert the USB connector. Which is a no-go. Because of this I mounted the FC up side down. This is no problem with the CC3D as you can fully adjust the board rotation with the software.


Flight controller attached and connectors soldered 

As usual I solder all the motor wires directly to the CC3D. This makes for a much cleaner install and avoids the 15mm protrusion of the servo connectors.

FPV camera and C filter

Yes. You read it right. I'm making a C-only filter for this build. There are two reasons for this. Firstly a coil can cause voltage spikes when breaking the circuit, for example when disconnecting the battery. This could effectively kill off your electronics. I am unsure of how big a concern this is but I should mention that I have it in consideration.

Secondly FatShark sells a filter, only at eight dollars, but I still consider it expensive since it is a small electrolytic capacitor and a tiny ceramic capacitor. The size of the ceramic capacitor is actually is actually the same as the one on the TS5823 that was deemed to small and improved in the V2 because it was noisy. 

Now FatShark makes premium products and all the FatShark stuff I have is great, so they can't be wrong about this can they? No. I'm trying it out as well. This time the filter will get no coil and we'll see how that works out.

The C filters

As usual the FPV side of the power system gets a bit cably and together with the filter it turns into a triangle style harness with power from the filter to the camera and to the transmitter and then a third cable with video signal from the camera to the transmitter.

Wire harness for the FPV system

Unlike the last build I've finally gotten hold of some M2.5 nylon spacers and screws. I used them to mount the board camera on the camera mount. This worked out really well. The M2.5 nylon is a bit rare, even on ebay where you'll find it from a few vendors. But it is well worth having it in the drawer when you need it.

Camera mounted to the board

Receiver, transmitter and sensors

I mounted the radio systems altogether onto the inner side of the top plate of the frame. It got a bit crowded and I would have like to spread them out more but due to my preferred placement of the antennas they end up together in the middle.

Receiver, transmitter and current sensor
Rx, VTx and current sensor

The FatShark VTx is a bit clumsy in comparison to the mini VTx I prefer using on small quads. The antenna is attached in the back of the quad and relayed via the antenna cable to avoid stress on the transmitter connector during a crash. Because of this the transmitter cannot sit in the back of the cage end ends up in the middle.

Similar reason for the placement of the receiver. To avoid interference from the video transmitter antenna the receiver antenna should be in the front of the frame (I'm unsure if the argument really is valid). To avoid the long antennas on the Futaba receiver to extend unnecessarily from the fuselage I tend to mount the receiver more to the back of the frame.

Together with all this comes the current sensor. I regret not having soldered a longer lead to the battery connector because then I could have placed the sensor in the bottom read part of the frame.

Result

Once the radio is in place there is not much more to do then close the lid and screw it together.

Finished quad
Assembled ghost FPV250

I'm currently waiting for a replacement LED board and until then I cannot tighten the screws on one of the motors. Tuning will have to wait. But as soon as it is finished I'll tune it and fly it.

Final weigh-in
The weigh-in
The quad turned out heavier than I expected. It is almost 80 gr. heavier than the 250 scrap build and this make a big difference to performance in a mini-quad. However, one of the reasons is the bigger and heavier motors, which will compensate for that. Other reasons are the two telemetry sensors, the four extra LED boards and the cables that go with them, the heat sinks on the ESCs and the bulkier FatShark video transmitter.

Flight videos and power consumption data will be added as soon as I get the spare parts and get it tuned in.

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