Getting the micro radio working

This evening was spent getting my radio setup working. This micro radio from hobbyking is very cheap, and seems to be working fine. However, the documentation is lacking, to say the least.

First of all, my servos and the radio has the power and signal leads completely backwards. This meant that I had to unhook the leads from the servo connectors, and insert them in reverse order. Not terribly difficult, it's just a matter of using some sharp tool to lift the small plastic hook holding the leads in place, while pulling the wires out. Then just push them back inside in the correct order.

The leads should pull out with no resistance after lifting the plastic hooks

The binding was confusing. You have to connect channel 1 and 5 using a wire that comes with the radio, and then bind using your favourite hitec A-HFSS compatible transmitter. I'm using an Aurora 9x.

Set the transmitter in bind mode for a Minima, and wait for the green led to flash rapidly on the receiver. This worked fine. However, connecting the power/ESC to channel 3 after binding did not. The LED started flashing green again (it's supposed to be constant red when getting a signal). After some trial and error, connecting the ESC/power to channel 2 seems to do the trick.

Here's a video of my setup in action:

I guess I am running out of excuses to postpone the actual buidling of the plane now...

Don't try this at home

Just a quick update. I finally got the last JST connectors for my 2s 450mah batteries, and I threw together a ragtag balance + charging cable. It will short and burn down my appartment, I am well aware. However, it also pumps current into my batteries, which is, as we all know, far more important. I repeat; Do not try this at home. Ever.

Some soldering work

I finally got my bullet connectors last week, and today I finally got the motivation to solder them. Things are progressing quite slowly with the micro plane, and I am still missing at least one set of connectors for the battery, and possibly a new balancing port for the 2s lipos.

Anyhow, here's todays results. I really need to get a shrink tube set.

Gonna have to shrink tube these at work tomorrow!

Time to build!

After quite a long while of thinking about eventually doing a Guillows free flight-to-electric conversion, I finally got pretty much everything I need to do the build. I'm still missing some connectors, but they should arrive soon. Regardless, I now have the essentials to actually start the assembly!

Sweet tiny parts of joy!

Landing gear progress

Just a quick update on the printed suspension landing gear I'm working on. After getting a shipment of PLA plastic, I'm finally able to print some precision parts. The ABS warping prevented any real mechanical parts from being printed.

The principle is fairly simple; one piston using a ballpoint pen spring and rubber bands attached to a joint that is connected to the plane and the wheels.

This is one side of the assembly

I still need to improve some of the parts, for instance I have to add a rubber band crossing between the two legs to absorb some landing energy. Otherwise, I'm pretty satisfied with the design so far, and hopefully I will have time for a real flight test before the snow sets in.

Sunday project: printing a house!

One of the things that were on my list of things to try with the 3D printer was something from Minecraft. Today I did the first attempt, and it was a great success.

I built this quickly just to have a test print

I used the Mineways export software to select my house from the Minecraft world. It has really good configuration for the exported model. I chose a block height of 2mm for this house, and exported to STL which I then sliced normally.

Selecting the box to print is quite simple using Mineways

The print itself took about an hour with ABS plastic, and it's surprisingly cool looking. I guess the only thing to do now is to build something cooler than a 5 minute house, and see how it turns out!

The finished result

Draft be gone!

After battling with ABS warping, I finally canned any dream of ever using my living room dining table again, and built a draft shield for the printrbot on it.

It's not the prettiest thing ever, but it gets the job done. Observe the printed filament hole in the cardboard. And with proper cleaning and hair spraying between prints, I finally seem to get bigger ABS prints that are not completely broken from warping. I'm still reluctant to call it without printing some more big parts, though.

On a side note, I ordered some glow in the dark PLA filament today, which should make for some interesting prints. I'm also still waiting for my supply of regular PLA to arrive. The small roll provided as a sample with the printer is running low, hence all the ABS whining. When I get the PLA I will probably play around with it for a while before touching ABS again.

ABS woes and printing landing gears

As I mentioned previously, my printer was having issues keeping the heated print bed at more than 92°C after relocating it to my living room. I fiddled around with a couple of ideas, and realized that the ATX PSU that came with the printer was only 400W.

After slaughtering an old PC, I salvaged a 650W PSU, and installed it in the printrbot simple metal. This helped dramatically with the temperature, and the printer now keeps around 100°C for the print bed.

The ABS plastic is still warping a bit for larger objects though, I'm suspecting that there is a draft along the floor. I intend to play around with various ways of shielding the print area during the weekend.

Anyhow, I promised a time lapse of a print. Here's an attempt at printing parts for a suspension landing gear I'm making for my Cessna 172. Notice how the right leg warps.

Octoprint and Raspberry Pi B+

Let's get this out in the open: 3D printers make quite a bit of noise. And they run for extended periods of time. And they produce quite a bit of plastic fumes. A combination that does not fit well with having one right next to your workplace (the computer).

Luckily, there are alternatives. This weekend I went on a shopping spree, and acquired everything required to run the excellent 3D print server Octoprint on a Raspberry Pi B+ . It should run just fine on a model B as well.

My printers new home

The installation was painless, just download the Octopi image and burn it directly to your micro SD card. Plug the pi into your home network, and you're pretty much ready to print.

Getting the USB web camera to work took a bit more effort. I had to tweak the parameters to mjpg-streamer to run in YUYV mode, but after that it worked perfectly.

The server itself is accessed through a web application, accessible at http://octopi.local or just the assigned IP of your Pi. Configuration is relatively simple, and you get all the familiar controls such as temperature, homing axes and gcode loading + printing.

One cool feature of Octoprint is that you can instruct it to create time lapse photos every z-level, since it is in direct communication with the printer. This gives you some really nice videos where the object appears to be rising out of the print bed without the distracting movement of the XY plane. I will make a post with a video as soon as I have a decent one to upload.

The interface is simple and intuitive

All of these features are nice and useful, but the main benefit of this setup is that the print is unaffected by your computer. You can reboot it, crash it, kill it or reinstall your favourite operating system 3 times over without ever disturbing your 5 hour print, which is important. One mid-print crash is quite sufficiently irritating.

I did run into  a problem moving the printer into the living room; it's quite a bit colder. This, in turn, makes the heat bed struggle to keep 92°C, which has made ABS printing quite sketchy. I will have to either move the printer to a warmer location, build a hotbox or improve the power supply for the heat bed in the near future. The jury is still out on which option I will choose.

As a summary: Octoprint + Raspberry Pi is super cool and useful, and if you have a 3D printer you should consider getting this setup ASAP.

More fun with the 3d printer

So I'm still in the process of playing with my printrbot simple metal, and figuring out what its limits are. I'm still getting some bad prints with the ABS, but as long as I remember to clean the bed and re-apply the hairspray between prints, things are good.

Yesterday I made a couple of joke-badges for me and a co-worker. The design was fairly simple, but I also experimented with paining the prints, with what I consider a moderate success. There's still something to be said for fine tuning the finish (possibly smoothing with acetone), but it still looks pretty cool.

A couple of fun badges

I also printed a couple of other test objects from Thingiverse, and this AngularJS keychain by Kim Gressens. In lack of red filament, I painted the red part of the chain.

Pieces before assembly. I had to scale the outter ring slightly up in Slic3r to make them snap properly together

The finished AngularJS keychain

Printing ABS on the printrbot simple metal

After dialling in the printrbot simple metal using the sample PLA filament that came with the unit, I thought I'd give ABS a try. I knew from multiple sources online that it would be more tricky than printing PLA, and my first attempts caused some concerns, with lots of warping and prints breaking loose from the base.

There are two important factors when printing with ABS. First of all, the bed has to be at a much higher temperature than for PLA, recommended is at the 100-110°C mark. Now, the bed you get from the printrbot upgrade kit will not reach this. I can get mine to read around 94°C, and this is just fine.

Another important thing to remember is that your kapton tape is going to need some additional adhesive in order for the ABS to stick to it. I first printed using a regular old glue stick, which worked surprisingly well. It did, however, leave a pretty nasty mess on the tape that has to be cleaned up between prints. It's also very difficult to get an even spread when printing, and it leaves some residue on the item. But it works, if that's what you have ready.

One successfull ABS print

The second, and current, adhesive I tried, is hairspray. Yes. Spray for hair. I know. It's downright absurd, but it works like a charm. It still leaves some residue on the kapton, and you do have to clean it with Acetone every now and then, which is some nasty stuff, but it is a lot easier to work with. It also lasts for at least 3-4 prints with pretty much perfect adhesion and no warping, so I'm very happy with it.

Two ways to make things stick

The ABS items themselves feel a lot more solid than the PLA, and it's nowhere near as brittle. This being said, it's a lot more flexible, so if you need a really hard plastic, PLA probably is better. But overall, it seems very much like a better option.

The cylinders are hollow, the printrbot handles overhangs pretty well

Building a printrbot simple metal

As you tinker with various hobby projects, inevitably the idea is going to pop into your head; it sure would be nice if I had a 3D printer to make this custom part that I need. It is immediately followed by "nah, it's not really necessary", and you discard the idea as unrealistic or find some other reason no to buy one.

Well, I recently had one of those thoughts, but this time, I was unable to repress it. So I plunged into a short, but frantic, period of scanning the internet for reviews, feedback and information regarding the various options, I finally landed on the Printrbot Simple Metal kit. So this week my kit arrived by UPS, and it was time to assemble the printer.

Firefly class

The instructions on the printrbot webpage are detailed and easy to follow, and the estimated time for assembly was surprisingly accurate (down to the minute). Even when combining two step-by-step instructions, one for the heated build platform and one for the printer itself, there were really no places to go wrong in the assembly. Tested.com made a series of build videos . Note that these were made before they updated the assembly instructions.

It is possible to order a pre assembled version of the printrbot for a small addition to the price, but frankly, I found the build process quite entertaining and educational as to how the printer operates. That being said, if you feel uneasy about the assembly process and the tweaking, this printer, or any other in this price range for that matter, might not be for you yet. It seems to be a quite common conception that in order to have your printer operating properly, some level of tweaking will always be necessary.

Now, I'm still in the initial phase of configuring my printer, but it pretty much printed an acceptable object straight off the bat. Using the recommended starting configuration file for slicer, it printed quite decent PLA objects.

Heated bed installation

The heated build platform add on available through the web shop seems like an absolute necessity from what I can see. It makes the plastic stick down fairly effortlessly, with no need for excessive taping between every print as I've seen people do on non-heated printer beds. Only the provided kapton square is required.

Supposedly, the printer should also be able to handle ABS plastic with the heated bed, but so far I'm having a bit of trouble making it stick. the bed doesn't quite reach the desired temperature of 100°C (I can only get it to around 94), and the ABS lets go of the surface fairly easily during the print. I will continue tweaking and trying this out in the upcoming weeks.

All in all, I am extremely happy with the simple metal, and I'm looking forward to experiment with using it for some actual projects relatively soon.

All the parts ready for assembly

The finished printer printing

The first print, without any configuration whatsoever

Hot glue gun controller

As much as you wish to build all your foam models with epoxy and other light weight glues, sometimes you just really want to use hot glue for a quick bond. Unfortunately, if you're using a cheap glue gun, as I do, it's more than likely that it doesn't have a thermostat to control the temperature. And, when working with a material such as depron, this usually means that at some point, the glue is going to melt the foam.

After several hours of cursing and (ignoring) waiting for the glue to cool off to a usable state, I finally decided to do something about the issue. Now, the cheap and probably smart way to do this is to use a dimmer switch, and lower the current by increasing the resistance of the circuit through the gun.

However, that somehow did not seem like the most interesting way to solve this problem to me. So, ignoring the obvious solution, I decided to finally learn some electronics and make an Arduino-based feedback controller.

You can get these really cheap on Ebay, and they seem to be working just fine

My original idea is quite simple, connect a temperature sensor to the glue gun, and use a relay to control the power to the gun. As the plan grew (and I continued ordering semi-random components from Ebay), I also added a volume knob to control the target temperature, and an LCD screen to show the current status. For this project, I'm using a really cheap Chinese Arduino Nano.

One of the early breadboard prototypes

So, ordering all the components I needed from Ebay, I started designing the circuit. It's fairly simple, but being the electronics novice that I am it took me a few tries to solder everything together in a proper fashion (I also had some soldering iron issues along the way, so it needed to be replaced).

One of my early attempts at designing the circuit. It's still missing a few parts at this stage

Basically, I have a thermistor rated for up to 290°C attached to the hot end, and using a voltage divider I'm reading the temperature at the tip of the nozzle. I then compare this to the temperature set through a rotational potentiometer (a volume knob). When the current temperature reach the set limit, the controller will go into a cooling mode. This kills the power usign the realy, and waits for the temperature to drop 3°C before turning the power back off. These two values are displayed on the 20x4 LCD screen.

After attaching the arduino nano to the breadboard

I designed a box to fit everything in and cut it out from 4mm plywood. I made the casing wide enough to be able to rest the gun either on the sides, or along the back edge of the top plane, but I haven't decided exactly where to put the holder for it yet.

Project box top plane with fittings for the volume knob and a 20x4 LCD screen

The last issue that still has to be solved is how to properly attach the thermistor to the nozzle of the gun. Right now, I'm using a heat resistant silicone, but it has almost no thermal conductivity, causing the thermistor to heat and cool off slowly, leaving an undesired delay. I have ordered some kapton tape, and hopefully that will solve the issue.

Almost finished, just need to fix the thermistor attachment

I'll come back with some pictures of the finished assembly, especially the thermistor attachment, as I'm excited to see how the kapton works out when I finally get it. For now, I'm quite happy having a pretty cool way to control the temperature of my hot glue gun.

Foamie flight trip

I took my most recent plane, the RC Powers SU-34 and the F18, both from the V4 package, out for a spin this Sunday. The weather was calm, and the planes performed admirably.

Unfortunately, the wind increased throughout the day, and gave the F18 an unintended landing in some shrubbery. Luckily, it survived without any major damage. And I could probably have salvaged the situation had I remembered switching to 4x4 when the plane started stalling. Ah well, at least there were no dead toddlers with very recognizable aircraft sticking out of their skulls this time.

My previous concerns about the SU-34 stability seems to have been related to a faulty flap-to-elevator mix, causing it to wobble during the launch and transition to normal flight mode. Even with my less-than-perfect duct tape emergency fixes from the maiden trip, I at no point felt the plane doing anything I did not want it to do.

Additionally, I lost no canards today, which is good. Nobody likes losing canards. Especially not at the checkout counter of the grocery store. That sucks. Big time. Really.

All in all, I am very happy with both planes, although I still favour the F-18 purely on an aesthetics preference basis!

Part of me was hoping for a catastrophic crash today, so that I could take on the MIG-29 from the V4 package, but alas, it will have to be postponed yet another week.

F18 V4

Our favourite game: Find the plane and pray it's not deformed into grey goo!

If only I remembered the 4x4 when it counts...