Gimbal

For those who are crazy about aerial photography, or high quality FPV videos, you might want to consider using camera gimbals. Camera gimbals could be driven by brushless motors or servos. The choice between brushless motor, or servo based gimbals ultimately depends on what you have and what you need. Although brushless gimbals are very popular right now I still think there is a place for some of the servo based gimbals. So we will discuss the pros and cons of each type of camera gimbals for quadcopters, and other multicopters.

What is a Camera Gimbal and How does Gimbal work?

When quadcopter is flying, in order to to maintain balance either automatically or manually, the motors changes speed to adjust roll/pitch/yaw angles. Therefore even with the best balanced aircraft, you will still see some level of shakiness in your video. By using a cemera gimbal, it compensates the change of roll/pitch angle, and leaves  the camera steady so you have perfect images.

Camera gimbals can remove some of the shakiness by stabilizing all three axes (Pan, Tilt, and Roll or sometimes just 2 axis) with the help of brushless motors or servos, and sophisticated sensors and micro controllers. You can freely move around with your camera and the Gimbal will keep it steady.

Also vibration from the motors could translate to the gimbal, if the copter shakes up and down that camera will shake up and down as well. When the shaking is in sync, it’s not as bad as they will cancel out. But when the shaking frequency is not the same (out of sync), it will result in terrible image, what we call “jello”.

Do I need a Camera Gimbal?

If you don’t care about video quality and it doesn’t bother you, you don’t need one.If you want one, your options are basically servo driven or brushless motor driven gimbals.

Servo Gimbals are generally cheaper, and lighter. Most flight controllers can handle servo gimbals so additional controller and sensor are not needed for this type of gimbals. However Brushess Motor gimbals give you better result, smoother image quality. I will try to explain further in the following article of the goods and bads of both types of gimbals.

Servo Gimbals

First impressions of the Servo based gimbals are, cheap, and light weight.

However they give amateur looking results, you can still see some jittering in the video due to overshooting movements. It’s a mechanical limitation of the servo. They are also slow to react because of the fundamental structure of a servo. More complex servo and Digital metal gear servos might be better, but then it gets expensive.

The light weight feature is very good for RC air-planes and quadcopters, also many flight controllers support servo gimbals, so you can just plug the servos directly to the FC, and don’t need to worry about additional controller board. Brushless gimbals usually require a separate control board, and sensor.

I personally like using servo gimbals for my FPV cameras where video quality is not essential. When I just want to be able to turn the camera horizontally and vertically using my radio transmitter, so I can look around in the air.

Brushless Camera Gimbals

Apart from being the opposite of the above, you cannot deny the video quality offered from a brushless gimbal is better. The reaction is fast, and the movement is very smooth.

However if you only mainly shoot photos then you can save some money and weight to use a servo gimbal.

Conclusion

Overall I would suggest that you go for a brushless motor gimbal if you plan to shoot aerial photography type of video, whenever you can. ‘Weight’ is one of the most important factors with multicopters, you can flight longer for every gram you save. Take a look at the experiment I did earlier about weight and flight time.

Both types of camera gimbal work, the question is which one do you need. I can see there is a decrease in the price of brushless motor gimbals, some can be as low as $60. If you ask me is a $120 gimbal better than than the $60 one? The answer is most likely to be “yes”. But is it twice better? Probably not.

No matter what gimbal you use, balance it before power on. It makes a HUGE difference.

Anyway, many people consider camera gimbal as a “luxury upgrade” than a “necessary upgrade”. In exchange of getting better quality recording video (hopefully), you will lose something in return. It doesn’t make flying easier, safer, or more fun, but adding extra weight to your aircraft, shortened flight time, and will cost you quite a bit of money. Not to mention in the case of fatal crash or fly away, you would lose more $$. So there are quite a few things to consider before clicking the “buy” button.

OSD Programming with Arduino

 



One great feature that we should add to FPV would be flight data on the screen display (OSD). By programming the MinimOSD, not only you get more accurate data on the screen, you can also select, edit what kind of data you want to have on the screen. The Crius AIOP board is supposed to work well with the MinimOSD, so I gave it a try.

I realized that you need a FTDI cable to do the programming, but if you happen to have an Arduino Uno like I do, then it’s your lucky day because you can easily turn your Arduino in to a FTDI programmer. I will show you how after the break. You can buy an Arduino from Newark.

Connecting Arduino with MinimOSD

How does it work?

A bit of technical background, skip if you like.

The Arduino UNO has an FTDI USB-TTL chip on it to communicate between a PC and the ATMEGA chip on the board. Because all of the necessary pins on the FTDI chip are connected to various pins on the edge of the board, we can just connect the MinimOSD up to the right pins and away we go! No need to spend extra money on the FTDI cable!

Let’s connect them

The connection is very simple. But first of all, if you don’t have an Arduino Uno but other Arduino boards, you need to make sure it has a FTDI chip otherwise I am afraid you are out of luck.

Connect your arduino to the computer, remember what COM port it has been assigned. Then unplug the Arduino from your PC.

Remove the ATMEGA chip from the socket. If yours is soldered directly to the board then you may still be able to continue, but you will also program the ATMEGA chip at the same time which you probably don’t want to do. This way we are just passing the data through the board to the output pins. Removing the chip means you won’t accidentally bugger up the ATMEGA chip.

Connect your MinimOSD to the Arduino board as follows:



Note that BLK on the MinimOSD is not connected to anything. Also note that TX is connected to TX, RX to RX – you don’t need to reverse them!

Connect the Arduino to your PC again. Your PC should recognize the device as usual and assign it the COM port we noted down earlier.

You should now be able to program the MinimOSD. However the way of programming it depends on the firmware, read on to see how.

Different Firmware for MinimOSD

Here comes the confusing part. There are some many different firmware suggested by people, I had no idea which one to use. After a lot of research, it turned out that we should flash the MinimOSD with different firmware, to work with different flight controller firmware. These firmwares are both open source, so it’s free to get them.

For MegaPirateNG, you should be using ArduCam-OSD, or MinimOSD-Extra. This firmware provides a very handy GUI tool, which allows you to flash firmware, and program the MinimOSD. All you need to do is to select the COM Port, browse to the firmware file, and click “upload firmware”.

For Multiwii, you should be using Rush-OSD. With this firmware you need to use the Arduino IDE to open the firmware files as a sketch, and upload them like you do with a normal Arduino.

It works great with this wiring diagram when using MegaPirateNG. But it just WON’T work with Multiwii for some reason. No matter which Serial port I plug the MinimOSD to, the ST LED didn’t light up, I get no image from the OSD. Although it’s working fine when testing with the Rush-OSD Gui and I can see the ST LED blinking. I think the Crius AIO Board is not talking to the MinimOSD, because the MinimOSD only accept certain data format (maybe telemetry data), and I couldn’t see any settings in the Multiwii config.h file either. After a couple of hours of trying and researching, I decided to leave it there. I don’t need it right now anyway.



I think that’s it, if I made any mistakes in explaining please let me know because I have only looked into this in the last few hours.

Thoughts about these open source OSD projects

I am sure the developers must have put much efforts and time into these projects, they do this not for money but for the convenience of others, and we are all very grateful.

However It’s not very straightforward to work these things out, because they are not well documented, and what is documented is not user friendly, at all. The “instructions are all over the place, you need to read through some 100-page long forum threads. Most of the time you need to guess, and do lots of trial and errors. After hours of trying only find out it’s not working. Very frustrating.

That is the problem with open source stuff, and sometimes it’s wiser to pay a little bit more and save the troubles.

LC-Filter

Einen LC-Filter benötigt man um die Störungen, die die Motoren und anderes stromhungriges Equipment beim Betrieb erzeugen, zu unterdrücken. Wenn man keinen Filter benutzt hat man oft Streifen im Videobild und in vielen Fällen wird auch die Reichweite verringert, da der Sender nur mit sauberer Eingangsspannung gut funktioniert.