Aerial Videos from a Toy Quadrotor

How to Mount a Mini DV Camera to a VL929 Beetle

This post is about how to attach a small video camera to a toy quadrotor. Around 2010, I was tinkering with the idea of building a quadrotor using parts scavenged from cheap coaxial helicopters. They contain a gyroscope, motors, gearing and rotors to use as the powerplants of the quadrotor, small lithium cells etc. So all the ingredients are there. Although the motors are brushed (but coreless), this does not matter much at these sizes, and actually at the low weights the speed controllers required would be prohibitive. The only requirement was to design a controller. 

I was surprised to see quadrotors in the similar configuration introduced to the toy and low end hobby market around the end of the same year. They contain small and abundantly available parts, and therefore are quite cheap. Walkera is a semi-brand in these circles, and recently has been producing fairly good quality models.  Their interesting model is the Ladybird, which uses direct drive DC motors and literally fits in the palm of your hand:

This is very nice and interesting, but around $100 or more, depending on the transmitter that it is shipped with. Also, the tiny direct drive props mean that the extra payload capacity would probably not be sufficient to lift a camera and its battery.

Soon after there were several imitations in the market. One of them, WL Toys V939 is a remarkable copy of the above:

VL Toys 939

It sells for $33.35 at banggood.com, with no transmitter, and about $50 with one, and free shipment worldwide. This is also remarkable. However, it is also direct drive. 

A variant of V939, however deserves some attention, the VL929 Beetle. This is a gear reduction version of the VL939, probably with the same motors, and the same gyro stabilizer. Gear reduction means larger, slower turning props which are more efficient at this regime of flight, and also mean greater load carrying capacity. The gearboxes have ball bearings, and the reviews are quite remarkable. The recent price of $40 including a 4 ch transmitter, cells, charger, spare props and free worldwide shipment meant that overall this looked like a good model! I ordered one and was quite impressed immediately.

VL929 also a Walkera clone. Even the sad insect face was copied...

The transmitter is not of great quality but it is quite sturdy. Actually my only critisisim is that the throttle stick does not have any damping. Also, you cannot get it to mode 3 (Mode 1 for left handed), so I had to open it up and do some soldering.

The model weighs 76g with 1S LiPo cell, and it can lift 134g. This means it has room for 58g of payload. For a keychain camera, this is quite sufficient. Things were looking good. I used a Tigers 600mAh 15C LiPo cell for it, which weighs 15g and costs $12 for 5 of them!

My version of VL929 is a new revision and did not have accelerometers in the controller, and only gyroscopes. I expected some attitude drift and a constant attention to level it. However, there is absolutely no drift and you can fly it all day with no cyclic inputs.

A few words about the camera. This is a generic camera module that records onto SD flash cards, with the model number Mini DV LK-D005

Incredibly with its own removable rechargeable Lithium battery, silicone sheath, simple tripod, belt attachment rig and similar stuff, it costs only about $18. Note that it brags "glass lens" at the front. However, the video is surprisingly good. It weighs 26g with battery, SD card and the plastic case, 15g without the plastic case. A quick check proved that VL929 was capable of lifting it.

So the problem was how to mount it to the VL929. The camera is slightly awkward because of the orientation of the lens. The first trial was to mount it on top of the VL929. After some thinking, I decided to cut off the top of a 500ml water PET bottle, melt some holes at the skirt so that I could fit it over the arms of the gearboxen. On the top where the cap goes, I rolled a paper tube and stuck in the camera, with its plastic case and own battery, together with some sponge to dampen the vibrations:

Camera mounted to the top with water bottle "holder".

This looked rather handsome. Straight off to test fly it. It did lift off well, and it did fly. However, the center of gravity was too high now, and it looked like trying to balance an inverted pendulum. Lots of oscillations and (over) corrections. The resulting video was OK to look at, but not really acceptable. 

The next step was to try to stabilize it by moving the camera to the bottom. In this configuration, surely the low center of gravity would prevent oscillations? Another mount was prepared using the bottom of a PET bottle. A window was cut to insert the camera at one side, and sponge in the center to dampen the vibrations. The camera was held against the sponge with rubber bands. To further "improve" the configuration and bring the center of gravity to the center of the body, I also removed the battery from beneath the VL929, and inserted it in the bottle in the opposite side of the  camera. Four holes at the sides of the bottle allowed it to be attached to the gearbox arms.

Camera looks out its own window and buttons and SD card can be accessed.

The battery at the other side for balance. All pressed against a sponge with rubber bands to suppress vibration.

Close up of camera and bottle attacment holes.

To my surprise, this did not improve stability by much. There was still a lot of wobbling and over corrections on my part. Another great idea into the bin. It was apparent that although the extra weight could be lifted, it was not doing much good for the stability. I had to lower the weitght, and also keep the center of gravity near the center of the model. Removing weight was possible by simply removing the plastic case of the camera (I could have got rid of the camera battery but that meant I would need to re-do the setup each time I connected the model battery which is not convenient; so I kept the camera battery). But how to lower the center of gravity? The angle of the lens made that impossible. When removing the case, I saw that the camera was not rigidly soldered on the PCB, but was actually on a flexible PCB. That meant that the camera could be rotated to any desired angle! This is how I modified the camera:

Camera with the body removed, camera module angled up, and battery fixed with some tape.

The sponge behind the camera module is to reduce vibrations. The camera PCB is not within the field of view. It may look flimsy, but it has worked very nicely for a month. To attach it, I made a shell by cuting out the bottom of a PET bottle, with the usual holes melted through for attachment to the gearbox arms. You can see that above also. The final configuration looks like this:

The camera is attached to the body with two rubber bands. Some paper napkin is between the shell and camera for vibration. It may not be necessary, and I will probably replace it with something better when I have the time. This configuration finally solved the problems of oscillations, and now it flies quite smoothly. Even outside, I could get some decent footage in mild winds. Remember this is a 100g AUW model, so it does get thrown around in even mild wind: