August 21, 2014

Next project, a cheapest mini quad?

The bench has a lot of things waiting. A 450 in need of landing skids and tail servo mount. A 550 in need of service and upgrades. A 250 in need of a proper gyro setup (3GX). A tri-copter in need of improved electronics and a fixed prop mount.

But right now I know other things that are more interesting. FPV quad copters of the smaller kinds! Having finished my second I realized both my mini-quads suffer from a particular drawback, the price. I did the math on my last build and ended up with a whooping $470. It sounds a lot but when you break it down and look at the choice of flight controller, the choice of telemetry radio and sensors, the choice of brand name video transmitter it is actually not that exceptional.

The biggest problem with this is that I fear of flying at certain locations knowing that a crash would be expensive. Areas such as over water or over dense underbrush. Battling this problem is easy, by building a cheaper machine, picking parts only (or almost only) based on price and what I already have in the drawers. I took half an hour today to put a build together.

  • Frame: Diatone FPV250 v2. I have gotten this one already to get the landing gear I lost earlier.
  • ESC: RCX SimonK 10A.
  • Flight controller: CC3D Clone. Yes, it hurts, but it's a better option than the equally priced KK.
  • Motors: RCX 1804 2400Kv. There are options at the same price, but I already have two of those.
  • Receiver: Corona R4FA-SB. There are cheaper 6ch non-sbus FASST receivers, but I already got one of those in the drawer.
  • OSD: Super Simple OSD. I'm going with OSD instead of telemetry. This is the cheapest one.
  • VTx: SkyZone TS 5823 200mW. There are cheaper ones but they usually don't work with Fatshark. This one I got already
  • Camera: Sony Super HAD-II mini

This configuration sums up to about $200. You can probably shave off a few dollars on the receiver, video transmitter and choosing a not so good camera, but this is as far as my compromises go.

August 18, 2014

Power distribution boards

I've never used power distribution boards for my builds but I did consider it for my last build but decided not to use one. I think that might have been a mistake, the build would have been easier with a power distribution board. Even though I don't use them yet, I ordered a few (since they aren't very costly) to get a good look at what they offer. I need a board which works with the smaller type of flight controller like the CC3D which narrows down the options a bit.

Power distribution boards

As you can see I even managed to two of the same kind. The middle ones are the same but with different colors and different brands.

The leftmost one is the one I actually need. It has the same dimensions as my CC3D board and will fit perfectly in a mini quad. It's rated at 50 amperes, which is probably not true, but even at half of that I still have a margin down to 20 amperes where my mini quads peak. I've only found those boards at HobbyKing so far.

The middle ones are essentially the crius board and a clone. They could have been a good pick. As you can see they have a double set of mounting holes, the outer ones which would fit a larger flight controller like the KK board and a set of inner ones. But the inner ones are too widely spaced for a small flight controller. If I find a board like this but with inner holes which fit the CC3D I will buy and use it.

The rightmost is a bit of an odd piece. It has built-in DC-DC converters (BEC). One rated at 12V and the other one variable 3-20V, which is practical. Sadly the placement of the soldering pads, with one pole at each sides, makes it more of a power board than an actual distribution board. With this board you'll still get cables going back and fourth, but you can loose one or two BECs from your build.

Edit: The middle boards are designed for the MultiWii controller which commonly has 35mm hole spacing whereas the CC3D and Naze32 has 30.5mm spacing.

August 13, 2014

Naze32 from HobbyKing

I have chosen to use the CC3D for my mini-quad builds lately. This is mainly because the Naze 32 has been hard to come by from time to time and that it is a bit unclear whether the board support S-BUS or not.

It seems the first argument just went away. HobbyKing just published their daily and they are now carrying the Naze32 under their name AfroFlight. I'll be ordering it as soon as I get my refunds for the orders I never got!

August 10, 2014

This is CopterX

My CopterX 450 failed miserably during its last flight. The tail servo mount broke in-flight. I had to take it down hard but managed to save everything but the landing gear. Lucky save I would say.

So what happened? Well, see for yourself. The tail servo holder does not seem to made out of the highest quality aluminium, that's for sure.

CopterX servo mount
Broken CopterX tail servo mount.

August 8, 2014

Simple LC-filter for the X900

I haven't been flying the X900 much for a couple of reason. Firstly it does not fly well with the firmware I loaded into the KK board. I haven't taken the time to fix this simply because the FPV system isn't working well either.

The FPV setup has a big issue with both jello and motor/esc interference. The jello problem comes from a prop mount which isn't straight. It came like that in the box but took me a while to discover the problem. Apparently I'm not alone with this issue. If you choose to buy the cheap NTM prop drives with accessories from HobbyKing, buy a few extra to save the 3-4 weeks wait for replacements.

I took care of the interference problem today by building a simple LC filter. I made it simpler than most recommendations and used only a solenoid and an electrolytic capacitor. This is mainly because I had no ceramic capacitors on the shelf. Next time, I'll put one of those into it as well to really really overdo it just in case.

LC filter on the X900. Sorry for the crappy image.

August 7, 2014

Using an accessory on the controller outputs on the CC3D

When using the CC3D board on a quad copter the controller has two left over outputs directly accessible on the board. The left over outputs can easily be used for gimbal output since the software has a built in configuration tool for it. But what if you would like to run any arbitrary device on this outputs.

First of all, you can use the Receiver port for PWM output. If this is an option, go for that instead which would be much easier. But in my case I use S-BUS which leaves the Receiver port empty and for installation purposes I would like to keep it like that, there is after all a PWM output with pins available.

I did figure out a way to use one of the output pins through the manual mixer for any arbitrary input channel. This way can also be used to use the flight mode channel (if you are short in transmitter channels) to mix it into an accessory output.

First I assign my channel to an input under the input tab. This is really simple and has full support in the GCS. Here I just pick S-BUS channel 6 to be assigned to the internal channel Accessory0.

The next step is to setup the mixer. This requires manual mixing and for some reason the GCS is somewhat limited here. But if you have already setup you craft configuration everything should be fine and you can fiddle with only a few values in the manual configuration tool.

I will use the ThrottleCurve2 as input to the mixer. Obviously, you wont be able to use that curve for flying any more. Under the configuration tab go to MixerSettings. Change Curve2Source to Accessory0, our channel 6. Then change Mixer5Type to servo (or whatever) and under Mixer5Vector type 127 into ThrottleCurve2. And thats it!

It seems that after having done this, the GCS GUI won't work for changing the mixer settings and you will have to live will the manual configuration from now on.

August 4, 2014

Diatone 17# v3, with power distribution built in

Having spent quite a few hours on the power distribution on the Diatone 17# v1 I stumpled upon an updated version. The Diatone 17# v3 has built-in power distribution in the bottom clean plate. If this build turns out good, that is what I'm building next!

I also noticed the Diatone 18#, which is essentially a very similar frame but not a clean-dirty design. And v3 has power distribution!

The Diatone frames are closing in on the blackout in terms of features. But do they withstand the same amount of violence?