Most hotel wifis are open, so to secure my connections I’ve set up myself a PPTP VPN using QNAS TS-453A box (btw. great machine, get one!) to tunnel all my traffic via encrypted connection.
Windows 10 and Android are connecting to the VPN and the traffic goes smoothly, but my Mac OS X El Captain caused me quite a bit of grief – it connected to the VPN without a problem, the internal connections were working great, but the forwarding traffic got stuck. Ping was working fine, but WWW did not. Some initial parts of first website were loading and then the connection got stuck.
The issue was caused by MTU mismatch. It seems that NAT on VPN server adds some headers, which cause the packet to be to big and get rejected.
Go to apple->system preferences->network-><your connection>->advanced->hardware and set MTU to Custom with packet size 1400 instead of default 1500. You may want to experiment to find maximum MTU value that works for you.
I love CloudFlare. Not only because it lowers the load on our servers and speeds up page load time, but it helps us to react to problems quickly. The most obvious case is when our server goes down we can redirect all the traffic to our spare server in a matter of few clicks. But today we used it to quickly fix a marketing issue:
Using CloudFlare I’ve set a redirect in few clicks. I know I could do the same using .htaccess, but in my book messing with .htaccess equals problems – it’s just too easy to break something there. With CF the fix was quick, instantaneous and totally painless.
After Windows 10 update of September, 2nd the WebEx stopped working – it is displaying following message: “Invalid input or system error. Please try again or contact your site administrator.”
WebEx ignores the problem as WebEx is not compatible with Windows 10 (in compatibility matrices and words of tech support).
There are two workarounds!
Use IETab in Chrome. When you connect to the WebEx from inside IETab it will reinstall the plugin and then connect correctly!
Use WebEx productivity tools to start new meetings or connect to ones you were invited do. Unfortunately this won’t work for meetings to which the invitation was forwarded for you – you must be on original list.
Last weekend I’ve added FPV camera and transmitter to my quadcopter. I’ve used FatShark 600TVL camera, ImmersionRC transmitter, minimosd OSD module (flashed for cc3d), FatShark power regulator and a cheap FPV camera mount I got from ebay:
The camera mount requires two servos, which can be used to provide stabilization and view “forward” even when the copter is in deep tilt. CC3D flight controller can use those two servos – see “Gimbal” tab in OpenPilot GCS (ground station).
The build itself was a huge challenge:
* the camera does not fit the mount – I needed to cut the holder and drill a hole for a signal cable.
* the camera mount is designed to point forward. I hoped to hide the camera inside the frame so it won’t get hurt during a crash, but that was not possible – I ended up mounting the camera sticking out a lot.
* there are no mounting holes or slots for transmitter or power regulator, so I tied them with cable ties. They stay in place, but are not rock solid.
* all cables are too long, but I did not have spare plugs, so I could not cut and redo them. All the cables and wires look messy
The result can be seen here:
And here is a video showing the first fligh attempts:
And a longer, uncut version showing a lot of mistakes. It’s not easy to judge altitude with such wide angle lens, so I had few close calls with a ground.
Let’s start with something exciting – the final result! Say hallo to Bandit the Quad!
Building the Bandit was a lot of fun, but also a bit of frustration when I kept discovering I needed more things. Below you will find my final checklist.
Bill of materials
Frame. I used Emax 250 Nighthawk Pro Frame made from carbon fibre. 250 is a size class. It is supposed to mean that the distance between opposite motors is 250mm, but in reality the size is 280mm. Close enough I suppose. This size is comfortable to build and not scary to flight.
Motors. I used MT2204 2300KV outrunners. Two of them with clockwise nuts and two with counter-clockwise, which should keep the propellers steady.
Flight controller (FC). I used CC3D – small, open source based controller. It is inexpensive and has a very decent software helping to set it up.
Electronic Speed Controller (ESC). I used Emax 12A. The brushless motors require alternating inputs on three wires to spin. ESC is a component that translates PWM impulses from the flight controller to inputs for a motor. Those are smarter than they look – they are microcontroller based and their software can be updated. Mine use SimonK firmware, which seems to be a standard in this class of quads. Mine ESC have BEC (Battery Elimination Circuit), which provides power to the Flight Controller.
Propellers. I used 6×3 carbon fiber props. I do not like them – they look cheap and have scratched edges straight out of the box. Also the carbon fibre is very tough, so in case of unavoidable crash the motor may be hurt more that with a plastic prop which would just snap. On the other hand some say the carbon fiber props give less vibrations. I’ll probably will be changing them.
Radio transmitter (TX). I used Spektrum DX5e because I happened to have one. I like it – it feels good in hand and Spektrum is recognized as a good quality brand of RC.
Radio receiver (RX). This is a crucial component – it needs to work well with your transmitter and with the flight controller. I opted for Spektrum AR610 – one of the simplest and cheapest in line. It uses PWM communication with the controller, which is fine for now.
Power Distribution Board (PDB). In Quadcopters there are two almost separate set of electric systems: low current signals (RC-FC-ESC) and high current power to motors via ESC. PDB helps with the latter. You may use PDB or you can make the harness using wires (14AWG should be enough). PDB leaves exposed contacts which may lead to short-circuits, but it is easier to assemble than the harness. You choose.
Battery plug. I own few batteries with XT60 plugs, so I used the same in my quad. I bought one already soldered to a piece of 14AWG wire.
14AWG wires to connect the battery plug with PDB.
Battery. I used 2100MAh 3S LiPo from DJI Phantom. Most people recommend smaller and lighter ones around 1300MAh 3S.
LiPo Battery charger. Self explanatory
Mini USB cable. The flight controller needs to be set up from a computer. CC3D uses mini usb, not micro as phones do.
Battery straps. You need to fix the battery to the quad somehow. I used two velcro straps.
Heat Shrink. There’s quite a lot of things to solder and isolate. Heat shrink is much safer and looks better than isolation tape.
Cable ties. There are a lot of wires in the finished quadcopter and the frame offers no help in hiding them. My receiver does not offer any mounting holes, so I used the cable tie to fix it as well. I used few of 100x2mm and some of 150x3mm cable ties.
LiPo Charging bag. Rarely the LiPo batteries can cause violent fires. LiPo charging bags contains the most of the flames. Grab a bag, they are worth it.
Crocodile clips (see tips and tricks)
Soldering iron and solder. You will need to solder the motors, ESC, PDB/harness and a battery plug. I used 30W iron and I felt it was to small for the power cables.
Helping hand/3rd hand tool – you want the wires as short as possible, which means the soldering is harder than usual. Without the helping hand tool from Maplin I would be sitting here until next Christmas.
Heat gun. I didn’t feel using a cigarette lighter would be good for the machine. Heat gun is the cleanest way to shrink the shrink wrap. Go PRO and buy one!
Small spanners for the frame and propeller nuts. I used pliers instead.
Computer with internet access.
Multimeter – to check for the soldering work before connecting a real battery.
Tips and Tricks
ECS and motors have three wires with no information how to connect them. I soldered the middle wires together and then connected the remaining ones using crocodile clips in a random order. This allowed me to check the rotation direction of the motors before committing the proper joint. I happened to choose wrong order on 3 motors! You will check the rotation direction while setting up the machine in Open Pilot software.
It is extremely easy to scratch the carbon fibre with any sharp tools. I have made circles around few bolts where I used pliers instead of a correct spanner.
You can get a pack of 75 cable ties in three sizes for a £1 in Poundland. You want to have different sizes, so you would spend £5 in B&Q and £9 in Maplin to get them. And you will end up with many unused ties.
If you haven’t soldered the 14awg wires before practice it on a side before starting the real thing. I found this to be the hardest part.
Remember you put the shrink wrap before soldering ;)
The build took me two evenings after I have gathered all parts.