Category: Video

We’re still busy with administrative stuff and preparing everything for release so sorry for the lack of tech posts. Hopefully there will be more time for those later :-)

But we did spend one night this week trying out something that we have talked about forever: Using OpenCV to auto-pilot the Crazyflie. For controlling the Crazyflie from a Python scripts it’s just a couple of lines and then you are ready to go. Add some object tracking to that and you can make an autonomous Crazyflie…or you could make a crashing one like the video below… The video is shot using a Playstation Eye lying on the floor. The camera has good potential for tracking since it’s low resolution, cheap and can do up to 120 fps. The plan is to use the size of the detection to control the thrust and the center of it to control the roll and pitch.

Unfortunately the latency was too large for doing a control loop for roll/pitch/thrust so it crashes. But hopefully in the future we, or someone in the community, will have some more time to spend on this. We think that it definitely has potential!

Part of this test was also to have another project where we use the Crazyflie Python API to make sure that it can easily be dropped into other projects.


The last week we have been busy preparing for the presentation we had at the Øredev conference where we talked about the Crazyflie history and design. We had a great time and got to meet some fellow nerds and talk about technology stuff!

All the presentations and keynotes where filmed and can be found on the  Øredev site. So if you have 50 minutes to spare check out our presentation. Or just skip ahead until ~41:00 to see Arnaud stick a Crazyflie in Marcus’ hair…

As for project there’s not much news. We are still waiting eagerly for the pre-series units that will arrive in a couple of weeks.

We discovered a new key-chain video camera which is called the 808#16. It had gotten a pretty good review so we decided to give the video camera add-on hack yet another try. A while ago we tried it with a 808#14 but it didn’t work that well when we where running it directly from the Crazyflie battery. It shut down as soon as we used to much throttle and using a separate battery made it to heavy. We didn’t have to high hopes for the 808#16 either and when we discovered that the bare camera weight, no battery nor case, was about 9g we knew it would be at the maximum of what the Crazyflie could carry.  With high hopes we connected the camera directly to the Crazyflie battery terminal and gave it a try.

It worked! The camera didn’t shut down but as you can see the stability is pretty bad during take-off. Once in the air it is controllable but only barely. We haven’t tested the full flight time but it probably wont be more then 2-3 minutes. We are thinking of doing a test where we add 4 more motors “mirrored” directly underneath the existing ones to increase the payload capability. Would be nice to have that option and it should be fairly simple to do.

We are pretty impressed with the video of the 808#16 which still is very cheap. We bought the 808#16 camera with the D-lens which is a wide angle lens and that’s why the video has a bit of a fish-eye.

After the LED hack we are back with an inductive charging hack!

The idea of charging Crazyflie inductively is almost as old as the copter itself. Last week we received a Palm Touchstone charging kit that we ordered. Like many phone hacks using this inductive charger we dismounted the receiving coil and electronic and attach it to the Crazyflie:

As the Crazyflie has a power-management circuit, any supplied voltage above ~4.5V will make it charge, and as we have made some soldering pads available for things like this it was a simple task. The coil is very thin and light (about 3g) so the flight performance are not affected a lot by the change. The charger is working very well and provides enough current for charging. We charge with a little less then 500mA and we think the Touchstone can supply up to 1A. One possible problem though is that the copter has to be placed exactly in the middle of the charging station to be able to charge. The phone has magnets to align it to the charge station and on top of that the charge station is not straight but tilted. The magnets are way to strong to let the Crazyflie take off so we are trying to find a landing area design that would permit the copter to land in the right spot and still be able to take off again without the magnets, any ideas?

When I was shopping for some ink-cartridge at this Swedish accessory store named Kjell&Co I also bought one of these 12V LED lamps. I didn’t buy it to actually use it instead I bought it to have a look inside. I cracked it open when I came home and found, not so surprisingly,  a lot of LEDs and a step up converter with a current sensing mode. Since it was made for 12V AC I removed the rectifier bridge and a large cap to get it as light as possible. Testing it with a power supply reviled that it worked all the way down to 2.2V and at 3.7V it consumed about 0.5A. A bit to much for the Crazyflie so I doubled the current sensor resistors to get it down to 0.25A. Some soldering and some double sided foam tape and we suddenly have  a pretty bright lamp hooked up to the Crazyflie. Now we have a search&rescue device :-) or maybe just an UFO…

Let’s not forget the sensor poll. It’s a very close encounter with 55% wanting the extra sensors. We will keep the poll open until next week to see if it gets any clearer.

One Sunday in March when we met up to work on the Crazyflie we suddenly realized that we do a lot of developing and discussing when we meet, but we don’t actually do that much flying. After realizing this we spent most of the Sunday just flying and playing around with the quadcopters.

So what could we try that we haden’t tried before…well we could try to crash each other while we are flying around: Crazyflie dogfight! The idea is that you should try to push the opponent out of the air without being dragged with him/her. This is easiest done by flying above the opponent making his/her crazyflie unstable and crash, however it is easier said then done!

This is not the first time two Crazyflies crash into each other in the air, but it’s the first time it’s actually intentional! It was a lot of fun but it can quickly end if something breaks. This dogfight however ended up with nothing to repair :-)

While we are waiting for our prototypes to arrive, the ETA is the 18th of may which is a looong wait, we thought we would play around with the Crazyflie outside now when spring has finally reached the south of Sweden. The drawback with a quadcopter this small is that it doesn’t work that well when it is windy outside but the upside is that it is pretty durable which makes great for some crazy testing :-). This Monday it was very calm outside and we got the idea to throw it in the air and try to make a “throwing start”. From the beginning we thought, no way, but it actually worked better then we thought. Here are some of the clips of  the more successful attempts :-)

We also bought one of these very popular key chain spy cameras to try and get some on-board action footage. We removed the electronics from the casing, removed the battery and connected it to our battery instead. We even removed the mini-USB connector to save weight. It all ended up in about 25g including the Crazyflie which is OK. Now it is really starting to look as an insect of some sort…

Frame from onboard video footage

We managed to take a short on-board video but the camera doesn’t handle the battery voltage drop and resets pretty easily as soon as you hit the thrust. Maybe it is possible to power it from our stable 2.8V instead because now it is pretty useless. Also the view-angle is to narrow as well as the framerate being too low to get any good footage. We seem to have gotten the 808 #14 model which isn’t supposed to be the best. At least the Crazyflie is looking pretty mean with it attached :-). Further investigations will be done when we have some time left over.

We wish we had something interesting to write about, but recently we have just been cleaning up and reorganizing the Crazyflie firmware. We are doing this so it would be simpler to further develop the software when it is released. We have also been preparing the new drivers for the digital sensors so they will be ready when the next version of prototypes arrives within the next two weeks.

One funny thing we have though is this little teaser video we put together while testing the speed of the Crazyflie. It is not recommended crashing into something hard at this speed 8O

We realized the other day that we have spent a lot of time discussing issues and developing stuff and not so much actual flying. We haven’t even left the rockie piloting stage… So when we met up on Sunday we spent a lot of time just flying around and having some fun :)

Here’s a first cut from some of the video we shot.