Here’s the case after my best attempt:
It looks… bad. The paint coat is horrible and full of scratches and the screen is too big.
But worst of all, the screen is not bright enough in direct sunlight. Not even close. I don’t have a photo but after brief testing I’d say it’s unusable.
So I’m pretty disappointing with the result – I ended up with a big, heavy RC system that is too dim to be usable for FPV.
I searched for a week for alternative capacitive touch screens, preferable in the 5-7 inches range but found nothing bright enough under 100 euros.
So after a mild diy depression I got an idea that will solve at lease 3 of the issues – cost, bright screen and the RC size: use my Galaxy Note4 phone as the screen.
The setup will look like this:
- The quad will send video through 2.4Ghz, packet injection (a.k.a. wifibroadcast method) and RC stream through 433Mhz
- The RC will receive both video and RC data and relay them to the phone using another 5.8Ghz wifi UDP connection. The phone will decompress the H264 video using OMX (or whatever is available) and display it with telemetry on top.
- The phone will also act like a touchscreen interface to control the RC/Quad
Basically this is what most commercial quads (like Mavic) are doing. I’m sure the video link is 2.4GHz due to longer range than 5.8 and better penetration and the connection with the phone is done over a 5.8, low power link.
So the next steps are:
- Redesign a smaller case that will accomodate a Raspberry Pi 3, the RC stick and fader + buttons and wifi cards
- Write a quick android application that can connect to the RC and decompress the video stream
I’m building my new quad and thought to give the H-Frame a chance. It it more spacious and perfect for FPV because the props are not in front of the camera.
My previous quad had 10mm CF arms – so for this one I thought to go for either 8 or 6mm ones. I tried both and settled for 6mm CF as it seemed to provide enough stiffness and were 20g lighter in total.
Here’s some Design Spark screenshots of the quad:
It’s very small – 33cm motor to motor diagonally – and light at ~680grams.
The improvement over my previous quad is that is has a gimbal and bigger motors and still about the same weight.
The components are:
- Multistar Elite 2306 mini-beasts. They are great, perfect bearings, very powerful and light. Around 10 grams heavier than my the previous 1804 RCTimers but they will swing the 7×2.4 prop way more efficiently and the estimated flight time increased by 5 minutes.
- Flycolor Raptor 20A ESC. Very small and powerful. I trust them more than my previous 4-in-1 RTFQ 12A ESC.
- The usual Raspberry Pi 3
- A TL-WN722N wifi card for the view link
- My custom Flight Controller on top of the RPi
- A MultiStar HV 3000mAh battery
So in the past 2 weeks I actually built it and it’s ready to fly. Here’s some photos:
Motor and ESC
Raspberry Pi mounted
The quad put together. The antennas are still temporary
The ESC and the cover with cooling holes
Frame with motors, one ESC and the Raspberry Pi mount with vibration dampers
However, it will probably never fly as the frame allows a lot of twist. It’s not rigid enough and to be honest, a bit messy. I don’t like the way it ended up and that twist really worries me.
Here’s a video of the issue:
So this was a failure. I should have known this before building the whole thing…
There are several solutions like adding more plastic between the arms to help the CF tubes, or switching to 8mm tubes. But I decided to switch to a X frame and be doe with it.
I’ve been working on the new case for the past 4 days and I have the first results.
The old case was too big, too crammed and it didn’t properly address vibration. The new case is smaller and lighter – thanks to the odroid w and includes better vibration damping. Also I will include damping at each motor mount.
Last night I printed the top and bottom plates and they are indeed small – the size of my palm. On top there will be a protective case and on the bottom a power box – with the battery + ESC.
The wifi card will be under the odroid, antenna pointing back. I have both whip and cloverleaf antenna mounts printed. The cloverleaf ruins the nice shape of the case as it is huge @8cm diameter.
The whole setup weights at around 600g, battery included. I should be able to get 25min of flight time with a 3S 2200mAh battery.
I also figured out a nice way to mount the blue wonder motors. I’ll go over the details in a future post.
3 weeks ago I did some vibration tests with all the motors at half throttle and I realized I really need to properly isolate the IMU. I was getting +- 8G in all the axes most of the time. This was driving crazy my AHRS code so something had to be done.
It took one week of designing and printing a new case but I managed to incorporate some dampers.
Here are some pics of the case:
The case with the sonar and Dtotek 10dof IMU mounted. The imu sits on some spongy double-sided tape.
Now the the raspberry pi on top:
This is the Quattro ESC + Alfa wifi board that will be mounted on top of the raspi.
The whole case is mounted on the frame with 8 vibration dampers that I recovered from a some camera gimbals.
First test showed a big improvement. Accelerometer vibration dropped to +-1G but now I get some low frequency oscillation in the gyro, probably due to the resonance frequencies of the dampers. I will try soon to put some ear plugs in the center of the rubber dampers to see what happens.
Cover still WIP.
It tool only 3 tries to figure out how to pack everything. It weights 30g without the electronics and 180 with the raspberry pi, crius board, ESC, WIFI and sonar.
There are 4 layers. First the sonar, at the bottom. Then the ESC and the raspberry pi. On top of them there is a plastic bridge holding the WIFI card and on top of it there’s the crius.
At the front there is space left for the camera with its servo.
The motor wires will go below the ESC board – there are around 15mm of clearing there.
So far it looks like the quad will weight around 820g – including the 3s 2200mAh battery. My old quad weighted around 1100g, mostly because of the heavy 450 frame and the gimbal. I calculated that every 40g gives me an additional minute of flight so I should be able to fly for ~20 minutes withe the new setup. And this is without considering the new bigger props – 10×4.5 vs 9×4.5 which should make the motors a bit more efficient at hover speeds.
This morning I started putting the quad together. I need to print the electronics case to fit all these:
1 – Raspberry pi – the brain
2 – Crius AIOP v2 – the io_board with all the sensors
3 – The Quattro ESC flashed with BlHeli with closed loop control
4 – The Alfa 036H wifi card
6 – SR04 Sonar
and the rpi camera of course.
The voltage/current sensor is missing from the picture.
Packing them in a small encosure while also keeping weight low will be tricky..
Here’s a few pics with the quad as well. It has 10 inch props and Suppo 2208 motors. The arms are 10mm carbon fiber booms. The motor mounts are printed on my prusa I3 and they also act as legs.
The whole frame weights 130g and is 54cm diagonal motor to motor. This is less than half the weight of my old F450 frame while being way stiffer.