Building an FPV Racing Quadcopter, Part 3

By Terry Dunn

Today, let's talk about assembling the components of the First Person View (FPV) system, as well as the camera used to record in-flight videos for our Strider Mini Quad.

Through the first two articles of this series, I assembled the bulk of the Strider Mini Quad frame, installed the propulsion system, and configured the flight controller. This time around, I will concentrate on the components of the First Person View (FPV) system, as well as the camera used to record in-flight videos.

The FPV System

The components that I chose for the Strider’s FPV system are quite common. The camera is a PZ0420 with a 2.8mm lens and IR filter. It mounts directly to the camera mounting plate that is provided in the Strider kit. The mounting plate is then sandwiched between the center plate and top plate of the frame. Since the center plate of the Strider frame features an integrated Power Distribution Board (PDB) there are 5-volt and 12-volt power taps for the camera located directly behind the camera mount. There are also inputs for the video and audio (if your camera has it) signal wires from the camera.

The camera I used does not have audio capability. It includes a 3-wire pigtail for power, ground, and the video signal. I shortened the pigtail considerably to reduce unnecessary wire on the airframe. The camera can accept 5-17 volts, so I plugged the pigtail into the 12-volt tap of the Strider.

My video transmitter (VTX) is a TS832 5.8GHz 600mW unit. Like most VTXs for FPV, it requires a FCC amateur radio license to operate. I attached the VTX to the bottom side of the top plate using self-adhesive Velcro. The rear end of the Strider center plate includes another set of power taps and nodes for connecting the video and audio signals. I again used the 12-volt tap and video signal.

I upgraded the stock VTX antenna with a circular polarized model. I also added a 7cm long extension between the VTX and antenna. The extension provides a flexible link between the antenna and its mount on the VTX. This isolates the VTX from the hard knocks that the protruding antenna is bound to endure.

When you are shopping for VTXs, antennae, and accessories, be sure to pay close attention to the gender of the connectors. Some components use standard SMA connectors, while others use reverse polarity (RP-SMA) connectors. You want your equipment to have the minimum number of connections and adapters, so get equipment with compatible connectors from the start.

THE PZ0420 CAMERA FOR THE FPV SYSTEM FITS PERFECTLY ON THE STRIDER’S CAMERA MOUNTING PLATE.

The goggles that I use with the Strider are from SkyZone. I replaced one of the receiving antennae with a circular-polarized antenna that matched the antenna on the VTX. One of the reasons that I chose the SkyZone goggles over others is that they have a camera integrated into the front of the headpiece. By pushing a button, I can toggle between the aircraft FPV view and the headpiece camera. In practice, the integrated camera provides a very wide field of view that makes it tough to see anything unless it is very close. Even though that feature was a bust for me, I think the goggles work well for FPV.

The Strider includes an integrated On-Screen Display (OSD) that overlays data on the FPV view seen in the goggles. Think of OSD as a dashboard. It shows the pilot a flight timer, real-time amperage, RSSI (see part 2), battery voltage, LED/alarm status, and amp-hours consumed. It’s all very useful information to have. There is also a crosshair icon that the pilot can enable and disable via a switch on the radio transmitter.

A 7CM EXTENSION BETWEEN THE VTX AND ANTENNA PROTECTS THE VTX BOARD FROM DAMAGE IF THE ANTENNA IS JOSTLED IN A CRASH.

Recording Video

In addition to the FPV system, the strider includes a mount for an action camera. This camera can be used to shoot photos or record HD-quality video of your flights. The camera mount is a carbon fiber plate resting on three rubber vibration isolators. All sorts of different action cameras could be used, but the plate is ideally configured for a Mobius Action Cam.

I MADE A SIMPLE ADAPTER TO ANGLE MY MOBIUS CAMERA UP SLIGHTLY. IT COMPENSATES FOR SOME OF THE FORWARD TILT REQUIRED TO ACHIEVE HIGH-SPEED FLIGHT.

The isolators are made of a very soft rubber, which makes them good for their intended purpose. However they can easily pop out of their mounting holes in a moderate crash…with the mounting plate and attached camera ending up who-knows-where. I looped a ziptie through each of the isolators to prevent this scenario. The technique for this job is explained in the Strider’s manual.

Knowing that the Strider would be tilted forward for much its airborne life, I decided to make an adapter plate that would keep the camera level during forward flight…or “level-ish” anyway. I made a wedge-shaped adapter using a scrap piece of thin kydex sheet and bolted it to the camera mounting plate. I attach the camera to the adapter with a combination of self-adhesive Velcro and zip ties. The wedge tilts the camera upwards about 10-degrees, which seems to be a good compromise.

I had my wide-angle Mobius attached to the Strider for the first several flights. I realized that I use the camera for lots of other jobs, so I didn’t really want it anchored to just one model. So I swapped it with my standard lens Mobius. I’ve logged a few flights with it so far. I still need to compare the footage from both cameras and see how I like the view provided by the standard lens.

Completing the Strider

Once I had the FPV and video systems squared away, I could complete the final assembly tasks of the Strider. I carefully positioned the top plate of the frame to make sure that I wasn’t pinching wires or compressing any of the electronic components. I then bolted it into place.

I had previously mounted my Futaba R617FS radio receiver to the bottom side of the upper plate with Velcro, but I needed a way to orient the receiver’s two antennae. I initially made a pair of antenna mounts from scrap nylon spacers, but I wasn’t happy with the results. My buddy, Fitz Walker, looked at a few existing designs and whipped up a simple mount that he 3D printed for me. Fitz’s design clips on to the top plate with a snug friction fit. The antennae pass through existing holes in the plate, into the mount, and outward into standard antenna tubes. It’s a much cleaner and more attractive solution.

THIS CUSTOM-DESIGNED, 3D-PRINTED ANTENNA MOUNT CLIPS ON TO THE STRIDER’S UPPER FRAME PLATE.

The top plate has a thru-hole for mounting the VTX antenna. The mounting location meshed perfectly with the position of the VTX and the 7cm antenna extension.

I currently fly the Strider with a gaggle of ElectriFly 3S-1300 30C LiPo batteries. I may step up to 4S batteries down the road for more power, but I’m very happy with the quad’s performance on 3S voltage. The battery mounts to the top side of the upper plate. I use Velcro between the plate and the battery, as well as a Velcro strap that wraps around both.

For safety reasons, all assembly and set-up of the Strider was done without props attached. You don’t want an errant setting to cause one or more props to unexpectedly spin up on your workbench. When all other assembly was complete, I installed a set of Gemfan 5x3 props. I used white in front, red in back. This arrangement is like the lights on a car and gives me one more point of reference to maintain orientation when flying by line of sight. I bought a selection of props in different sizes and colors, so I may deviate from this configuration at some point.

My final task before taking the Strider out for a test flight was to locate any wires that could potentially foul the props. I zip-tied the motor leads in two locations on each arm. I also made sure that all of the receiver, CC3D and VTX wires were properly routed and secured with zip ties.

WITH THE UPPER FRAME PLATE REMOVED, YOU CAN SEE THE MOUNTING LOCATIONS FOR THE R617FS RADIO RECEIVER AND TS832 VIDEO TRANSMITTER. NOTE THE NUMEROUS ZIP-TIES USED TO SECURE EXTRA WIRE.

The power leads for the battery took a little more thought. With some experimentation, I found that I could remove most of the slack in the battery cables by routing them around the left post of the radio antenna mount. I could also secure the battery cable by wrapping it under the battery strap, but that method is a little tougher to do.

The Strider is now ready to fly!

Up Next – The Fun Part

In the final article of the Strider build series, I will provide an overview of my initial test flights with the Strider, adjustments that I made, and my impressions of what it’s like to fly a quad racer.

Terry spent 15 years as an engineer at the Johnson Space Center. He is now a freelance writer living in Lubbock, Texas. Follow Terry on Twitter: @weirdflight