Squirt v2 with DJI FPV

By wrong17 on Mar 28, 2020

8  406  6

Squirt v2 Re-Build

This is my first build using the DJI FPV system. I will be taking my existing Squirt v2 analog video equipment and replacing it with the new DJI digital stuff. But first, I will go to my favorite website Thingiverse to try and find some parts to make my conversion easier. I was lucky enough to find something I really liked. The guy who designed the parts did a really good job and I especially like how the air unit module is hanging under the top plate. Then the camera is moved to forward so ducts are in view.

This time around I went with a full GoPro case because my camera took a beating with only a half case. I also moved the crossfire antenna to the GoPro case because it did not seem to have the greatest reception when it was in the rear.

I honestly think that using the DJI system makes the build process a lot easier because there are less wires needed to be soldered to the FC. But it is a pain to figure out where to put the air unit’s control module.

The problems I had when rebuilding the squirt is that I could not get my HGLRC F420 stack low enough where I could use the original 30mm standoffs. So, I end up using a 35mm standoffs instead and it gave me plenty of space to work with.

Next up are the 90-degree MMCX connectors DJI used for the antennas. I had a difficult time plugging it in because the TPU printed mount was in the way. I did not want to modify the 3D model and print and another one, so I just took some cutters and snipped away any excess material that was in the way.

And finially, make sure you install the ducts right before you screw on the top plate because it will block the holes for the camera.

DJI FPV Goggles

Since this is my first time using the DJI FPV system I will a make a few comments about it. I did not know what I needed to do but it was very straight forward and surprisingly the manual outline it very well.

  1. Fist you will need Activate the hardware (air unit and goggles) via USB and Computer (download and install the software from DJI’s website and the link is in the manual https://www.dji.com/fpv/downloads)
  2. Then it will update the firmware
  3. Finally, you link the 2 together.

And there you have it, it was that simple.

Before I even start using the goggles, I already modified it to fit my needs. First off, both the original and new upgraded foam did not work for me. So, I end up using some other foam that I bought in on Amazon that was meant for the HTC VIVE VR Headset. The fit of the goggle is way better, but I still need to work on the light leak in the nose area. The best part of all is that is not like a sponge that soaks up your sweat. The foam is like fake leather, so it super soft and you can wipe off any oil or sweat with ease.

I do not like to carry the battery for the goggles in my pocket because I always forget about the cable connects to the goggle when I take it off. I got use to how Fatshark has their battery on the strap and I wanted to do the same with the DJI. I end up getting the Ethix beige strap and 3D printed an adapter so I do not need to do any permanent modification to use the Fatshark style straps.

Another way to do it is cut a slot in the goggle’s metal ring so you can slide the strap in, but do not want to hack away on my brand-new goggles. So, the next best option would be the 3D printed adapter.

Betaflight 4.1
I was kind of worried about switching my firmware to 4.1 because the HGLRC F420 stack is considered an older setup. The last time I plugged it in to do anything, I was still using Betaflight version 3.5.7 and I used the suggest PID tunes that NurkFPV had in his orginal Squirt (Nov 2018). I am glad to say, BF4.1 worked flawlessly with my stack and I was able to get the OSD data to the DJI goggles.

Around the sametime I built the squirt, NurkFPV released a new video on youtube called "How to Build a Cinewhoop Drone for Cinematic FPV Shots in 2020," that was published on March 26, 2020. I did not come across that video until today (March 30, 2020), but in the description of that video he included a link to his website that shows his PIDs. But as of now, I am using stock BF 4.1 PIDs and the rates NukeFPV uses:

RC Rates for Roll, Pitch, and Yaw is: .80
Super Rates for Roll, Pitch, and Yaw is: .80

The reason why I even started with this PID and Rate setup is because that is what Rotor Riot has on their Squirt v2 (Joshua Bardwell's Youtube video "Best Cinewhoop" Jan 29, 2020). I do have to say, the stock PIDs seems to work pretty well so far. I will update this page later when I try out NurkFPV's PIDs.

Flight Times
After doing a bunch of flight test on this rebuild, I have very happy with the DJI FPV system. The FPV video quality is amazing and it is difficult going back to analog now. Without a doubt this is worth the investment, however; it does come with a heavy cost! The flight time have suffered significantly. Now, I only get about three and half minutes of flight time, compared to the five plus minutes that I use to get. At first, I thought it was my old 4s 850mah lipos were getting tired, but then I tried some brand new lipos and still got the same flight times. As of now the only lipos I have tried are:

  • Tattu 850mAh 4S 14.8V 75C (~104g)
  • CNHL MiniStar 850mAh 14.8V 4S 70C (~110g)

How much flight time will I gain with a larger capacity lipo, if any at all. Here are 2 lipos I plane to use:

  • Pyrodrone Graphene 1000mAh 4S 14.8V 95C(~145g)
  • Gaoneng GNB 1300mAh 4S 14.8v 120C (~166g)

After my first flight with these brand new lipos, here are my flight times. As a side note, I unknowingly over discharged the lipos trying while I was trying to maximum the flight times.

  • 4:50 - Pyrodrone Graphene 1000mAh 4s – 1030mah was charged back in to the lipo
  • 5:20 - Gaoneng GNB 1300mAh 4S – 1242 was charged back in to the lipo

This is only a test to see how the Squirt will do with larger capacity lipos and if it is able to carry the extra weight. This is not a scientific test, nor did I stop each flight when it drops to a specific voltage. As you can see I flew the Pyrodrone Graphene lipo beyond the rated capacity.

New Flight Stack
After a minor crash I neglected to see that battery wires ended up in the pops. When I tried to take off, it started to slice and dice the wires. Both the positive and negative wire were exposed, and it cut through the current sensor. I am guessing the current sensor wire might have touched the positive lead because the FC is no longer responding. After repairing the wires, when I plug in the battery the start up tones will begin but not finish.

This would be a great opportunity to try something different, like a BetaFPV 20a AIO tiny whoop format board. I 3D printed a 20x20 to Whoop board adapter and everything else was straight forward. After everything was mounted up the total weight ended up being 331g. I lost about 9g with this conversion. I think the weight difference is not from the 20x20 stack but also the shorter standoff. With the HGLTC F420 stack, I used 5mm taller standoff because the 20x20 stack was too tall and the DJI air unit would not fit. So, when I switched to the TW board, I can go back to the original standoff.

This was a short-lived test that I should have given it more time to fine tune it. Overall, it flew fine but it felt kind of awkward because I was having some strange problems that I have not encounter before. The first problem is the voltage reading was off or not working. About 2 minutes into the flight the voltage was stuck at 3.6v and 4 minutes into the flight I started to losing power because my lipo was completely drained. With the default setting from BF version 4.1.5 it was not as smooth as with the HGLRC F420 stack. And finially, it seems to have more latency with the FPV feed than I any of the quads that has the DJI system.

Before putting the TW 20a AIO board in, I originally planned to switch to a Talon F4 v2 and Aikon AK32 35a ESC. Then the TW AIO board arrived in the mail and I thought I would be interesting to try it on the squirt. As you can see, it did not work out so I when back to the Talon and AK32 setup. I was able to keep the stack under 16mm tall, so now I can mount the DJI Air Unit on top of the 20x20 stack without needing longer standoffs. The final weight is now 337g with the Talon F4 v2 and Aikon AK32 35a ESC.

Photos

Part List

Frame

Shen Drones Squirt V2 3" Cinewhoop Frame - Carbon & Hardware Only (Ducts Sold Separately) - Choose DJI or Analog (10 builds)
Racedayquads.com
$38.00

Flight Controller

HGLRC F420 F4M3 FC OSD / 20A BLHELI_S 2-4S 4IN1 ESC
Pyrodrone.com
$62.99

Motors

4 x BrotherHobby Tornado T1 1407 3600Kv Micro Motor3600kv (196 builds)
Racedayquads.com
$63.96

Propellers

Azure Power 5150 - 3 Blade Propeller (Set of 4 - Polestar Blue) (2 builds)
Getfpv.com
$3.29

FPV Transmitter

DJI Digital FPV Air Unit - Ultra Low Latency 720p 120FPS Digital HD (85 builds)
Racedayquads.com
$179.00

Receiver

Team BlackSheep TBS Crossfire Nano RX - Heli-Nation (568 builds)
Heli-nation.com
$24.99

Batteries

Tattu 850mAh 14.8V 75C 4S1P Lipo Battery Pack (XT30) (34 builds)
Getfpv.com
$18.86

Radio

FrSky Horus X10 Radio (Amber)
Getfpv.com
$375.99

Goggles

DJI Digital HD FPV Goggles (46 builds)
Getfpv.com
$529.00

3D Printed

Shendrones Squirt Parts by andyshen (2 builds)
Thingiverse.com
See Site

3D Printed

Squirt v2 GoPro 5 6 7 Variable Angle w/ Lens Guard by wrong17
Thingiverse.com
See Site

3D Printed

Squirt v2 DJI installation kit by M490fpv
Thingiverse.com
See Site

3D Printed

DJI Digital FPV Goggle Strap Adapter by stsanford
Thingiverse.com
See Site

3D Printed

Shendrones Squirt v2 Variable Angle Gopro Hero 5 6 7 Mount Immortal T by wrong17
Thingiverse.com
See Site

HD Camera

GoPro HERO7 Black Action Camera (67 builds)
Getfpv.com
$399.99

Video Receiver

ImmersionRC rapidFIRE w/ Analog PLUS Goggle Receiver Module (129 builds)
Getfpv.com
$149.99

Radio Module

TBS Crossfire TX - Long Range R/C Link (11 builds)
Getfpv.com
$208.99

Battery Charger

HOTA D6 PRO Charger AC200W DC650W 15A (6 builds)
Pyrodrone.com
$119.00

Soldering Iron

TS100 Portable Programmable Smart Soldering Iron (145 builds)
Racedayquads.com
$51.29

Backpack

Lowepro QuadGuard BP X3 - Drone Backpack for 4 FPV Quad Racing Drones and 15" Laptop w/Exterior Mounts (Black)
Amazon.com
$286.00

Accessories

BoYz analog bay v2 for DJI FPV goggles
Themakerboyz.com
$23.98

Accessories

Analog FPV FatShark Module Adapter V2 for DJI Digital FPV Goggles
Pyrodrone.com
$11.99

Accessories

FuriousFPV Smart Power Case V2
Helidirect.com
See Site
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Discussion

Sign in to comment

troncat_fpv   29 days ago  

Where can I find a file of that adjustable gopro mount with the immortal-t mount on the back?? Awesome build!

wrong17   29 days ago 

I remixed that file myself. I can put it on Thingiverse, I will post a link when its done.

wrong17   29 days ago 
1

Here is a link for the GoPro mount: https://www.thingiverse.com/thing:4324964

troncat_fpv   27 days ago 

thank you!! amped to get this printed

M490fpv   Mar 30, 2020  

Looking really nice and clean! :)

wrong17   Mar 30, 2020 
1

Thanks! I could not have done it with out your designs on thingiverse. I am also using your Floss 3, 3D printed parts to mount the DJI FPV System on my quad.

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