26 March 2015
25 March 2015
This is a simple, low-cost amplifier kit based upon the LM386 amplifier IC.
It has a maximum output power of 1W, which is good enough for amplifying mp3 players, phones and also the beeps and sounds from microcontroller projects.
This kit has one surface mount component, the LM386, which is good for those learning to solder surface mount components. The rest of the parts are through-hole.
It is available for just £6 (including delivery within the UK).
24 March 2015
I've been designing a breakout board for the ACS758 hall-effect current sensor. The first few prototype boards came in and I decided to give them a quick test. The results were not quite as I expected so I thought I'd put write about them here, for others that might be using this IC.
These current sensors come in a number of ranges (50A,100A, 150A and 200A, all with uni and bi directional variants). They use the hall-effect, which measures the change in the magnetic field to measure current. This means you do not need to install a shunt resistor, with its associated power loss and voltage drop.
23 March 2015
22 March 2015
After Donkey Kong, Pacman and Lunar Lander we were having a discussion about which other games could be turned in physical versions. So about 6 months ago an idea was forming in my head, more recently I've managed to get all the pieces into the right place to make it happen and my physical version of space invaders was born.
I've document the whole project over on the sharks blog because I've used a Whitetooth laser cutter, a rotary attachment and a break in board.
So you can check out the whole project here
18 March 2015
17 March 2015
I have run a number of solar photovoltaic and off-grid power hands-on workshops and I recently ran another solar PV workshop with EWB Nottingham. This was a two hour workshop run at Nottingham hackspace.
Engineers Without Borders UK (EWB-UK) is a student run organisation trying to connect engineers with the field of international development. They do this through placements, training and outreach programs.
15 March 2015
While building my model SpeedTwin ST2 I needed to neatly cut some foam. Since I had a bunch of 6mm laser safe ply available and needed to cut some other bits the next day I decided to design my own hot wire cutter and cut the parts out at the same time.
The cutter is designed to be built around some 1/2inch spruce engine bearer stock that I had lying around. Any roughly 1/2inch square section wood will work so long as it is stiff enough.
Most of the parts are designed to be built from 6mm ply, with a few 3mm bits. 6mm, 3mm and 2mm bolts are used to attach the fittings to the wood. Some nichrome wire is used as the heating element, with some stiff wire on the other side to tension the cutting wire. I added some springs to help maintain the tension as the wire stretches. These would work better on the other side to that shown in the photos to increase the amount of wire available for cutting.
I’ve found lots of articles online about DIY hot wire cutters that suggest using a transformer connected directly to mains, with no current limiting or anything. DO NOT DO THIS. Those people are idiots (and they’re most likely in a country with a lower mains voltage). I’ve been running my hot wire from a lab power supply in current limited mode and it works nicely and gives excellent control over the temperature of the wire.
I’ve uploaded the DraftSight files to my GitHub account for anyone who is interested in them, but please bear in mind the finished product could be dangerous and I take no responsibility for what you do with it.
Foobot is a project I started around November 2014. It’s still a work in progress, but the time when I should have written it up is more than due.
Foobot is robot table football game, with two teams of two tiny adorable robots. The robots are controlled by classic Nintendo and Sega controllers, hopefully it can can finally settle the age old console wars.
The intention eventually is to build some games around these robots. Possibly with the ability for a computer to control some of the robots via some image processing if I’m feeling really ambitious.
The robots are built around an ATtiny2313 microcontroller, with an SN754410 to control the motors and a cheap 1402 433mhz radio receiver module. This is mounted on a simple laser cut perspex frame with two wheels mounted directly onto the motors.
The initial design was built on stripboard, but once I had it working I ordered a professionally made PCB via http://dirtypcbs.com/. This was the first PCB I’ve had made and the quality turned out to be better than expected for the price and the 3 week shipping was pretty bearable.
As the radio modules are very simple (and one way) I decided to avoid the problem of collisions between multiple transmitters by attaching the controllers for all players to a single radio transmitter. The transmitter reads all of the controllers and then sends a packet addressed to each robot in turn. Messages for the robots consist of a robot ID, the message payload and a checksum. Robots ignore all messages not addressed to them and any messages with invalid checksums. Dropped packets or interference are dealt with by hoping the next message with more up to date data will arrive.
The transmitter module is based around a tiny 8 pin ATtiny13 microcontroller. This has just enough pins to read data from all of the controllers and to send a signal to the transmitter module. Some of the lines are shared with the In-Circuit Programming interface for the microcontroller – these were chosen to be the outputs so there was no need to worry about other hardware interfering with programming.
In order to read 4 controllers with 4 pins the transmitter uses a pair of controller interface boards. These have a socket for a NES controller (which contains a shift register so the button states can be read out serially) and a 74LS165 shift register which enables the Master System controller to behave like a NES controller (it is just 6 buttons with a shared common pin). The 75LS165′s latch line is inverted so a transistor was required to invert this in order for the same latch signal to operate both devices.
With this setup the only extra pins required on the microcontroller are shared latch and clock signals and a data line for each NES/Master System controller pair. The serial output from the NES shift register is passed into the serial input on the 74LS165 so sending a latch and 15 pulses reads 8 buttons (2 unused) from the Master System controller and then 8 buttons from the NES controller. The Master System buttons are mapped so they come out in the same order as the buttons with equivalent functions on the NES controller (A, B, Select, Start, Up, Down, Left, Right and 2, 1, N/A, N/A, Up, Down, Left, Right).
In the case of the transmitter the circuit was initially tested on a breadboard. This proved quite fragile due to the flying leads to the various controllers so I ordered some more custom boards. The price break on DirtyPCBs is at 5x5cm, so I designed a single board containing the controller interface and a board to carry the microcontroller in a single 5×5 square. I designed tabs into the board outline to allow the two boards to be broken apart. When fully assembled the transmitter contains two of the controller interface board and one of the microcontroller board, so there will be some spares of the smaller board. The cheapest quantity from DirtyPCB is a protopack of 9-12 boards (I got 11 both times), but I only need one transmitter currently so that works out just fine.
I struggled to motors that are both cheap and small without a ridiculously high RPM. The motors I settled on in the end run at around 16000 RPM and 9 volts. Because of this I had to add some code to pulse width modulate the enable pin on the motor controller. Turning requires very little force so it runs with a very low duty cycle. When moving forward initially the motors run at full power to get the robot moving, after a short delay the duty cycle is lowered to avoid accelerating too fast.
Tuning the PWM settings has proven fiddly, and testing with the programmer attached is almost useless as the wires affect the motion of the robot too much. Because of this I implemented an over the air update of the PWM settings. This added some extra commands to update the PWM duty cycles over the radio, and a command to write the to the microcontroller’s EEPROM to save them permanently once the behaviour feels right.
I’ve uploaded the project to github, including all of the code, schematics, PCB layouts and chassis/case CAD files. Feel free to use these, but please bear in mind that the project is still a work in progress.
Finally, here’s a video of some Foobots in action (before the over the air PWM tuning feature went in):
Just a quick post, it's been a busy week I've been out delivering lasers to people for Just Add Sharks (more to deliver next week too). I also have a great monthly project I've been working on which is very nearly finished so please accept these simple meeples for the week :)
09 March 2015
Over the past two years a number of people have been working on a series of books for Engineers Without Borders placement volunteers.
These books are designed to cover the basics of the theoretical, practical and social aspects of doing engineering projects for devlopment. They are meant as a basic guide, a collection of case studies and links to further information.
I have helped co-athour the Energy book and it has been published and released as a free .pdf.
I'm very proud of the final result which, I think, is an amazing resource.
07 March 2015
Last design from this batch, this dual dragon pattern also looks great, incredibly intricate details but the laser just copes with like any other cut.
Some of the pheonix cut previously have made it onto shields and have been coloured and latexed. Those things look fantastic, there is so much potential for lasers in LRP weapons, a line of matching group shields like this would look amazing on the battlefield.
06 March 2015
05 March 2015
Terry from Occasions Boxed contacted us at Just Add Sharks asking if we could do a sample to demonstrate the capabilities of the Laser cutter. He sent me a well coloured raster image which left me scratching my head a bit. I little bit of creativity later and I came up with the above, he obviously liked it because he purchased a Blacknose over the weekend and I delivered and installed it on Monday
02 March 2015
Looks like I totally forgot to add the cutting video to the bottom of yesterdays post. It cut a bit too slowly and burnt through the wood rather than marking the surface, it also seems to be cutting sections twice (which I just noticed)
28 February 2015
As already mentioned I used the Lasermode Variant of GRBL, this is freely available and can be easily compiled and flashed to the device using the Arduino IDE. The only minor problem was that I had to use the most recent development branch of the IDE (1.5.8), but that has now gone into stable release (1.6.0).
GRBL is very clever, all of the machine specific settings are stored in EEPROM on the microcontroller. This means if you update the software all the settings remain on the device. All the EEPROM settings are adjustable using text commands over the serial port. Since the software is downloaded using the Arduino IDE it was easy to set up the device using its serial monitor.
The first task is to work out how many steps per mm the laser has. Read the settings to figure out how many steps per mm are currently being used, request the axis to move 10mm and measure how many mm the laser actually moved. When you know how many steps it took and how far it went you can calculate how many steps per mm the machine actually has. The Blacknose has 78 steps/mm on the X axis and 156 steps/mm on the Y axis.
The next task was to set the appropriate direction bits, GRBL has a setting to make sure the direction lines appropriately, the defaults are acceptable. Finally you test the homing cycle to make sure both axis run up to the limit switches and then stop. The image will appear rotated by 180 degrees because GRBL has the origin in the bottom left and the blacknose has it in the top right. It is possible to modify the GRBL settings to correct this but it hardly seemed worthwhile.
GRBL accepts G-Code sent to it via the serial port, so you need 2 additional pieces of software, one to create gcode from your drawings and one to send lines of gcode to the machine. There are numerous way to create G-Code but the one that sprung to mind was DXF2GCode. Most vector programs can output dxf so this solution is independent of drawing package.
It's a very simple offering, the file is loaded and displayed in the main window along with the origin point. You are able to turn each of the entities (drawing lines) on and off as required and you can set the feed speed for the drawing. Because it is intended for all CNC machines it includes options for z axis height but we can just set all of those values to zero. The file created contains a series of G-Code instructions that describe the imported image.
To send the G-Code to the arduino I chose to use Grbl Controller, again it's a cross platform solution and it comes with a few useful Jog functions to move the laser head around which makes it good for testing the machine. A handy text box allows you to type commands directly to the controller. You select the required G-Code file and it is sent line for line to the laser cutter. The laser cutter executes each instruction and cuts your required shape.
Results and Conclusions:
GRBL works on the machine, I was able to cut out the test pattern with only minimal editing of the G-Code. I was a bit worried about the response times, There seems to be a noticable delay between turning the laser on and moving the head. With a CNC mill or a low power laser diode this probably isn't noticeable (or may even be necessary to get the mill up to speed), but with a 40W laser this leads to a burn mark on the work piece.
The is no reduction of power as the laser goes round the corner, This is due to the G-Code being fed into the machine but ultimately it means the corners cut better/burn more than the straight lines when the laser head is moving at speed.
It's an extremely functional arrangement that was pretty simple to set up and get running, There was a bit too much manual tweaking to get it running with the big laser so it's probably best suited for small laser diodes. It's all a great learning exercise, next stop is a serious reduction to the amount of metal work on my laser cutter, before moving over to a Laseraur type controller (whatever that entails)
27 February 2015
26 February 2015
I shy away from Birch plywood, it's more dense than the poplar I love so it's useful for more structural things but it cuts slower so I tend to build strength into my designs. Kevin from Kitronik was telling me about their new supplier and how nice the new material was. So I bought some 0.8mm, 1.5mm, 2mm, 3mm and 6mm and I'm extremely impressed with all of it.
The last batch of birch I bought was fairly rough on the surface but it also had a fair number of voids and knots in it. Every time the laser hits one of these it doesn't cut cleanly and you have one of two choices, you can spend just as long freeing the thing up by hand afterwards or you can turn the power up and re cut it. Kitronik has really grasped the idea that quality is essential for laser cutting, I would happily pay a little bit more for quality wood that cuts first time because it's going to cost far more if I have to do it a second time. The best part of it all is that the high quality wood from Kitronik costs the same as the other stuff so there is no contest.
The second thing I've noted is how much nicer the 1.5mm ply is. On previous models I've had a really burnt and black edge and I've had to cut it slower than the 6mm stuff to make sure it cuts cleanly. I'm convinced this is because it was actually non laserable external ply, the Kitronik stuff really is laserable and uses internal glue between the layers so it cuts cleanly.
It's another rave review for Kitronik but with good reason. Get some birch (and Poplar (and Perspex (and Polypropylene))) for yourself, you'll be glad you did.
25 February 2015
24 February 2015
An open challenge has been set for the UK Maker Faire this year. Titled the Mega Fun UK Lasercut Challenge (@MFUKLC) the goal is to fire as many ping pong balls as possible at a target in a 30 second time frame.
Well the challenge has been set and busy or not there is no real way we can ignore it so I've had to get my thinking cap on. The competition states that we're only allowed to use an A0 sheet of material which means optimising all the parts to use the smallest amount of material possible. This is a first attempt at a ball hopper, my current launcher design has a lot of capacity but relies on a steady feed of balls so the hopper must hold as many balls as possible and allow them all out in an orderly fashion. This design is easily extendible to include as many rows/columns as required (svg here)
21 February 2015
I often get asked to answer questions for articles I never get to see or fill in surveys for research Continue reading
19 February 2015
It's very easy to forget how long it takes to go from prototype to product. Absorbing an awful lot of my time this week is a remake of my Settlers of Catan set. It's more than just a remake though, since I've used that set a fair bit now and there are things I wanted to change and improve upon. The photos above are 4 variations of the tiles, each one improves something different but they all take time. Set number 4 (bottom right) is the one that's ready to move forward but it's only a variant of the final set so there is yet more dev work to do.
Expect more on this in the near future.
12 February 2015
Mum and dad were always very generous to me, particularly when it came to toys that allowed me to explore my obsession with experimentation and construction. As quite young child I had got the “starter” Philips X20 electronics kit, which I played with a lot. Not too long afterwards, sometime in the late 1970s, and still as a pre-teen, I got the monster Philips Radionics X40 kit for my birthday.
For a child excited by technology (in a hands-on way, not the XBOX, iPad, App-store version of technology that many kids love today) the X40 was an impressive and exciting toy. It allowed you to build 40 projects – called “Experiments” in the manual – from testing to see whether water was conductive (boring) to regenerative radio receivers. The radios were the things I loved the best, particularly when dad and I had made special coils and we could tune it to get SW broadcasts. In the pre-Internet era hearing Voice of America and Radio Tirana was exciting.
As well as the radios the kit had some simple digital electronics. I learnt the function of all the basic logic gates from the X40. I also particularly remember a project which was a multivibrator driving a frequency divider. That project used all four transistors in the kit and seemed particularly sophisticated.
Dad put a lot of thought in to which system to buy and I think he liked the Radionics kit because it was open to expansion and the construction technique was very much like real electronics. The kit came with a large (A4 sized) PCB which was cleverly designed to work with all the projects. The components were mounted on plastic bases with brass screws that went through holes in the PCB to make the connections. Basically it was a solderless version of through-hole PCB construction and you got to see the real components pretty much unpackaged. When I went on to building projects on breadboard and veroboard it was an easy transition because I was so familiar with what things looked like from the X40.
I can’t claim that all the time I spent with the X40 taught me much about electronics theory. Even now I find the lumps of theory dished out in the manual rather hard to follow. At the time they were way over my head. What I did learn was a lot about practical electronics and also that electronics was an experimental science – you could just try changing stuff and seeing what worked. Also the presentation of the manual with the circuit diagrams and the physical layout side-by-side taught me to read circuit diagrams intuitively and that’s a skill that’s been really useful.
The connection with Philips seems to be a bit tenuous by the way. The X40 and other kits in the same range were rather confusingly co-branded “Philips” and “Radionics”. Philips had their own range of kits that was popular in Europe and as far as I can tell the X40 was a created by the UK Radionic company who I guess then applied the Philips brand under licence.
For the fundamentals of electronics using bipolar transistors I still think that the basic outline and structure of the X40 projects is very appropriate, so much so in fact that when I designed by Electronics for Absolute Beginners course I took the X40 as the initial starting point.
I still have the components and manual for my X40 kit – one day I’ll have to build some circuits to show you. In the meantime, here is a scan of my manual (48MB to it’s big!).
I am not the only fan of the X40 on the web. Try these sites for more info, photos and manual scans:
- http://ee.old.no/library/ (Radionic scans near the bottom)
10 February 2015
08 February 2015
I had previously made a Laser cut Knob for the Blacknose laser cutter but I've been using it a bit recently and there were still a few issues with it so I redesigned it. This knob is 50% longer but that's 12mm on either side. On the top it makes it easier to grip without scraping your knuckles on the laser frame, on the bottom the knob extends beyond the square section to hold the shaft better, this makes it far less likely to slip off while in use. (svg here)
07 February 2015
It’s been a long time since I last posted to this blog, I’ve done a fair bit of brewing in that time but nothing noteworthy. (mainly kits) a few months ago I did another batch of ginger beer with the following recipe:
500g Light DME
Juice of 3 Limes + zest
Juice of 3 Lemons + zest
545g Ginger (Blended and steeped)
1tsp yeast nutrient
1tsp cayenne Pepper
Wilko’s ale yeast
OG: 1.050 sg
FG: 1.010 sg
For this one I tired using cayenne pepper which did add a little fire to the taste, I also upped the ginger which make the drink too strong and it required diluting with lemonade to be drinkable. I also blended the ginger which made it much easier to extract the juices.
I’m currently planning batch which I’ll give a more detailed post for than this. I’m dropping the ginger contents and somewhat going back to basics with batch 6 which should hopefully give something more immediately palatable.
05 February 2015
03 February 2015
Welcome to WordPress. This is your first post. Edit or delete it, then start blogging!
For the longest time I've been quite anti 3D printers. It's a lot of time and effort to end up with a noddy little plastic toy that's badly ribbed along the edges and could often be made easier with alternate tools (like a laser cutter). It's really about using the right tool for the job though and there are things that 3D printers can do better. So I used my Christmas money to buy myself a 3D printer kit so I could fulfil some very specific projects I have lined up this year.
I found a 3D printer kit on line that was very cheap (<£300). It's a variant of the Prusa I3 with a bowden extruder, something I specifically require. It would be very easy for me to knock this printer due to the poor assembly instructions but each time I think about but I find most of my complaints cancel out when I remember how cheap it is. All it really needs is someone in the UK whose built one to answer queries quickly and without the language barrier so I've decided to stock this 3D printer in my own webstore.
Buy your own 3D printer kit from me here.
From here on down I'll be documenting my own build experiences, I set myself 3 nights for building the kit and 3 nights for tweaking and getting a print. This is obviously an ongoing project but I achieved my first successful print at the end of the allotted time and I'm ready to move onto more prints.
The kit shipped directly from China, it weighs 6kg and comes neatly packaged in a cardboad box and pallet wrap so no chance of it getting damp on the journey. The gaps were filled with polystyrene and each component was individually wrapped. The build instructions/software are on a CD tucked inside one of the smaller parcels. The larger parts are laser cut and each of the brackets is 3D printed, a large chunk of the frame is still made with threaded rod and bolts.
The electronics package comes with all the common parts you would expect.
- 12V Power is supplied through a big PSU
- An Arduino Mega 2560 board is the controller
- RAMPS 1.4 connects to the stepper motor drivers, hot components and sensors
- A4988 stepper motor driver chips control the stepper motors
- J Head Nozzle
- Metal Heated Bed
- Stand Alone Print controller, print direct from SD card without a PC
- Large Status LCD displaying the current state of the system
Don't forget if you want to join me on the journey you can now buy the same kit through me.
01 February 2015
Made from 6mm Birch plywood, these arrows will be painted up and attached to a signpost mad Hatter stylee.
31 January 2015
A long time ago I was asked for a large batch of kotch snowflakes, it was mostly forgotten about until this week when the order actually came through. Amusing that it coincides with the large amount of snow we've been getting this week.
26 January 2015
I had a custom request to make these wooden disks from the Age of Enlightenment expansion for Settlers of Catan. They had seen my previous Catan Disks and felt that the expansion needed the same wooden token treatment.
20 January 2015
It’s a mystery.
I've got a large pile of useless machines sat in the garage taking up space and I'd like to move them along so I've dropped the price and they're now on sale for £15 each (maker faire prices).
18 January 2015
from Sunset Magazine, December 1961.
You can build one of these yourself… Instructions here:
17 January 2015
I wish Disney would actually produce t-shirts and the like based on things like this instead of me going to Redbubble, but they would rather sell lavender and glitter shirts.(Not that I mind that shirt that much, just, compared to this one…No.)
I love this shirt because it is so freaking nerdy. I mean, look at it. It’s a patent design for a car in an amusement park ride. That is then used in a haunted house dark ride that I’m in love with.
16 January 2015
We intend to be making a few announcements and featuring the work of our customers (and some of it is absolutely amazing) but we'd also like to feature work of other people. So if you have a hot tip for us on any laser cut item then we'd love to know about it. Let us know what you're working on and who else inspires you. Just send your emails to firstname.lastname@example.org
So the parts for the first of 12 projects just arrived. This is probably the one that's furthest from my normal stuff, but it will bear relevance as we go through the year. I'm planning a serious build day next week where there will be unboxing and assembly photos and probably even some stop motion of the day. Fun times.
15 January 2015
13 January 2015
09 January 2015
I've been wanting to play around with sending data via a mobile SIM card and, after needing to do it for another project, here is a short post on my attempts at getting it all going.
I used an off the shelf GSM/GPRS module (the SIM900).
I tried this using both the Arduino Uno and the Arduino Leonardo.
Here are the results from my tests.
07 January 2015
- Animations that are based on a single 'brightness' value so the patterns can be dimmed.
- Animations are intended to be 'non blocking' so the arduino can be used for other things at the same time (partial success with that).
- Animations are based on the number of LED's so by changing the constant a shorter or longer string can be used easily.
The software is all based upon the FastLED animation library, you will need to download this before the code will compile. (Code here)
06 January 2015
I was wanting to make an interesting lampshade as a specal Christmas present this year. I set about searching Instructables for inspiration.
This used a repeated unit which was cut out of polypropylene using a laser cutter.
05 January 2015
04 January 2015
For the past week I have been at the 2nd Wind Empowerment conference in Athens.
The conference was an inspiring mix of interesting presentations, hands-on workshops and social fun. Around 45 people from at least 10 countries attended.
Here are some notes and photos from the event.
01 January 2015
Following on from the rather successful 365 projects in 365 days and 52 projects in 52 weeks it does look like I'm going for 12 big projects in 12 months this year. These won't all be purely laser cut and potentially some of them may not include laser cutting but I'll photograph, document and share as usual. I made a list this morning of the big projects I want to complete this year and I'm already up to 8, I'm pretty sure the other 4 will just appear before the end of the year.
(edit: I already remembered another 2 I promised to do)
I promise I'll also find time to squeeze the usual amount of laser cutting around everything else too.
29 December 2014
A recent discussion started with the simple question “When is it New Year?”. Well, 1st January, right? The stroke of midnight on 31st December? Depends where you are on the planet? [depends what planet [if any] you are on]. It depends on which timezone you are in.
So, we settled on it being at the stroke of midnight for each of the timezones around the world. Which, surprisingly, is 30. Less surprisingly, they cover a full 24 hours.
Upon discovering this, the only decent thing to do seemed to have a drink to toast New Year all around the world. So, this year, I’ll be getting together with a few friends to see in the New Year – all 30 of them! If you want to join us, you can use the list below, or follow Brisbane Clock Tower on Twitter as it announces them live over the 24 hours.
If you do join us, please let me know where in the world you are and use the hashtag #NYEoClock in tweets!
Cheers and HAPPY NEW YEAR!
Yay for Christmas, I have lots of new toys and lots of new exciting things to do in the new year. I also have new products working their way through and (vast) improvements to old products, but if I'm so busy why no posting? Well Christmas happened so I had to move all my secret stashes of junk from places like the sunroom into the garage and then this morning I had a customer visit so I had to move all the crates out of the garage into the sunroom. It's not turmoil, more like organised chaos. The upshot is that I have some space in my garage to sort out this massive pile of junk. I'm going in and I may be some time.
Belated Merry Christmas and a Happy soon to be New Year.
28 December 2014
I’ve been neglecting this blog recently due to various distractions but have several projects I want to write up. Around April I found myself with the urge to build a multicopter. In the end I settled on a tricopter design as it’s a little unusual and because the wider angle between the arms allows plenty of clearance to mount a camera without getting the propellors in frame.
To keep costs down and because I enjoy designing things I ended up drawing and laser cutting my own plywood frame. This was loosely based on the folding arms of David Windestål’s design, with a lot of modifications to fit the size and shape I wanted and to fit the parts I had chosen.
The arms of my tricopter are cut from 3/8″ birch engine bearer stock, as sold in most model shops. I bought 3 12″ lengths which I cut off centre to make a set of 7″ arms and a set of 5″ arms. In the end I was happy with the 7″ arms so I’ve not yet tested the 5″ version.
The frame is designed to have two 3mm ply lower plates that the arms are sandwiched between, held together with 2mm machine screws. The screws are tightened so that the arms are held in place by friction when unfolded, but they can still be folded relatively easily without any adjustments or tools.
Following David’s pattern, the landing struts and motor plates are attached with cable ties. These hold everything firmly in place but will hopefully give or break before the frame components if too large an impact is applied.
Above the two structural plates of the frame there is a third plate with a large number of cutouts. This sits above the frame on laser cut plywood standoffs and serves to protect the electronics that sit on top of the frame. The KK 2.1 flight controller I’m using has a build in LCD display and buttons for configuration in the field. All of the buttons and the display are accessible through a cutout in the top plate. Additionally the plate helps with cable management, wiring being attached to the frame with cable ties and velcro straps to keep it neat.
Because I went for a tricopter design I required a swivel mount for the rear motor. This consists of a modified motor mount plate with two tabs on the bottom through which an M3 bolt is threaded. A pair of bearing carriers are formed from two layers of ply parts that slot over the rear arm with appropriately sized holes to trap a pair of bearings through which the bolt runs. The rear landing strut was cut with an appropriate cutout for the metal gear servo that moves the rear motor mount. This turned out to be a weak point and is so far the only part I have broken. A new design has been drawn up but has yet to be tried as the replacement rear leg is still going strong after many more landings (with slightly more care).
Electronically the tricopter is fairly simple, though there is a small hack to power the rear servo. Each speed controller includes a voltage regulator which normally powers the other equipment that needs 5 volts. Since there are multiple ESCs in a multicopter, only one of these is required. People cut the 5v wire to prevent the regulators from fighting (probably only necessary with switching regulators). The KK 2.1 board simplifies this as the first ESC connector powers the board and radio reciever while the 5v pin from the other 7 are isolated so no wires need to be cut. This does mean, however, that no power is provided to the servo. To work around this I modified the rear ESC by desoldering the 5v wire and removing it from the connector. I then soldered a 3 pin header to the voltage regulator output to make the 5v and ground lines of an additional connector. The 5v wire from the original connector was attached to the third pin of this and at the other end plugged into the signal pin from the servo output on the KK 2.1 board. This provides a connector on the rear ESC into which the servo could be plugged, providing power and the appropriate signal to drive the servo (see diagram).
Very few changes were required to make the tricopter fly nicely, with the exception of increasing the proportional gain for roll and pitch without which the controls felt quite sluggish.
I have some video from an early test flight shot using a cheap 808 keychain camera. I’ve since bought a Mobius and added an appropriate mount but haven’t had chance to get any footage with the new camera due to weather. The downside of building the tricopter from wood is I don’t want to get it wet!
Reciever: Hitec Optima 7
Flight Controller: KK 2.1
ESCs: Turnigy Plush 10A
Motors: Turnigy Multistar 1704-1900kV
Rear Servo: Turnigy TSS 10-MG
Battery: Turnigy 1000Mah 3S 20C LiPo
I’ve made the drawings from which the tricopter was built are available to download and I’d enjoy hearing about it if anyone uses them in a project.
27 December 2014
Just in time for the holidays: An archival container for Chesterwhite, the UI Libraries’ first web server (1994-1998), now taking up permanent residence in the University Archives.
THEY ARCHIVED THEIR SERVER.
IT HAS A CONTAINER AND A CATALOGUE NUMBER AND EVERYTHING.
MY FEEEEEEEEEEEEEELINGS. I WANT TO HUG IT FOREVER AND REMIND IT HOW IMPORTANT IT IS.