Category Archives: DIY

VP multi-rotor: development testing

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I figured I should put together a list of what the development tests I want to do before setting out to actually build a prototype of a VP quad. The temptation is high to just build something, but I know I will learn a lot more by doing some testing ahead of time in a controlled environment.

Would like to build 2 test stands. One based on Trex450 heli parts and another based on Trex500 heli parts. Both are available in belt drive or torque tube, both are available from HobbyKing and hence are quite inexpensive.
The rigs need to be modular enough to test both belt and torque tube designs.

What I would like to test:

– How much power can be handeled by either torque tube and belt drive

– Failure mechanism at high power. (what fails first?)

– How much does the boom flex (carbon vs aluminum) as this may impact the effectiveness of the torque tube?

– Ability to test out different blades (length, profiles) at different angles of attack, and record thrust vs RPM vs angle of attack.

 

What I will need:

– some sort of I/O card for data acquisition so I can record in real time things like RPM, blade angle, voltage, current, thrust, displacement/bending of booms,… (add more)
Preferably a USB solution so I can use a laptop to do the data recording on Labview?

– a test rig that can accommodate the data acquisition parameters. Also needs to be  inside a lexan or mesh enclosure so failure testing doesn’t hurt me.

 

Rig Design:

I will start with a heli body, since i will be using all the gearing inside the heli body and stick a motor in side
Figure out the gearing first.

AF Assist v5 – optics

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Since I will be using off the shelf parts for the IR emitter (LED), I need to somehow focus the wide 100deg or 120deg light given off by the emitter.
The light wavelength I’m looking for is in the low 700 nm range as measured from two Canon flash units.

I’ve found an IR emitter that puts out more then enough light at 730nm (1080-1293-1-ND from Digikey).
To focus the light in a tight beam, I just ordered some parts from Newark.

The lenses are

– LEDIL  FP11055_LISA2-RS-PIN  LENS,ROUND,1 POS,9.9MM OD

– LEDIL  FA10888_TINA-RS  LENS,ROUND,1 POS,16.1MM OD

– LEDIL  FA10886_TINA-0-PLUS-RS  LENS, REAL SPOT, GOLDEN/PLATINUM/DRAGON+

I’m hoping one of these small lens with enclosures will do the trick.
Will post more once I get them and try them out.

The light out of the bare LED is way to wide, and these lenses should focus the light to a tight 10-16deg beam.

AF Assistant v5.0 – First look

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It’s been a while since I posted an update on this project. Life gets in the way sometimes, but I’m back at it now.
The previous design enclosure that fits under the camera has been abandoned mainly because it makes holding the camera a little awkward. Especially when using some longer lenses when I need my left hand to grasp the lens itself the AF Assistant would not only get blocked (by my hand) but also make holding the lens a little weird. Continue reading →

Keeping track of projects

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For projects where ordering parts is a necessity (like from HobbyKing), I should keep track of why I ordered each part and what its intended use will be.
I guess this should apply to most other projects. Keep track of progress, and just generally keep a log.

Enclosure for CNC machine

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I’ve been spending some time thinking about a method to enclose my CNC machine.
There are lots of ideas… (pictures). (another link) (enclosure build log 01)

One key thing is that I want easy access to the CNC table so I can easily add heavy items like vices, rotary tables, etc. And the encluse needs to be somewhat modular so that I can take parts of it off in case I want to work on/service the cnc machine.
The three sides (left, right and back) will be plywood construction. That part was easy.

The chip/coolant tray was the second hardest part to figure out, but I think I have a design for that.

Thirdly is the front door to the enclosure.  Since I have walls on the left and right side, the width is set. My initial thought was to make side-to-side sliding doors using full extension kitchen drawer slides. Depending on how large I wanted the opening to be, I could use either one sliding pane (per side) or two nested panes (per side) to allow more of an opening. For a door system that uses two nested doors per side, I would need  4 pairs of slides. Each pane needs 2 slides; one for a bottom track, and one for a top track.
But then I came across these Over The Top Slides.  I can make the door as wide as I want, and flip it up and push it over the top in one motion. Or if one door gets too heavy, split the door into two. Only drawback is that the slider only comes in 14″ lengths, which means it can only accommodate for 14″ of travel. Continue reading →

Variable Pitch multi-rotor craft

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A post on RCGroups got updated last night. A new variable pitch multi-rotor craft got posted, and it looks very slick. This got me motivated again in continuing my work in this field.

While looking for the heli parts that were used in the above post, I came across this RC helicopter manuals collection of helis I never heard before. It’s good to know about it and see how other helis are designed and put together, for future ideas.

http://macgregor.co.uk/support/heli-manuals.htm

AF Assistant IR 1.0

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Work on the new AF Assistant has gotten to a point where I thought I would post some progress.

First off, the name is slightly changing. I am calling this one the AF Assistant IR. This will be version 1.x
As the name implies I am working on using an IR lightsource (well, near IR) from a Canon 550ex. I have mounted the LED module in a case which sits under the camera. It mounts to the 1/4-20 threaded hole on the bottom of the camera. The unit is still triggered by the remote shutter release port on the side of the camera just like the AF Assistant v3.1

Fig 1. Pattern at 3 ft.

I have chosen to align the light so that the projected pattern of the module is horizontal (as opposed to the vertical line the laser  AF Assistant put out). Due to the fact that the pattern is not just a line, and that the module is closer to the lens axis then a hotshoe mounted device, parallax errors in alignments are quite small. It seems that (in the first alignment of the LED module), the center focus point can pick up  on the projected pattern from 3ft to infinity. That’s more then enough for me. I can probably tweak it to get a closer distance, but I’ll play with that later.

Fig 2. Pattern at 30ft.

Several advantages are already apparent by using the LED module.

– The pattern that this puts out is quite wide. So wide in fact that with a 50mm lens on a full frame sensor (of a 5d mk2) the side (left or right) focusing points are able to use the pattern.
– The light the LED module puts out is quite dim. Figure 1 (at 3tf) was taken at ISO6400 , 1/30, f1.4. Figure 2 (at nearly 30ft) was taken at ISO25600, 1/13, f1.4. In a totally dark room, at 30ft, I can just barely see (with the naked eye) the pattern on the wall 30 ft away.

For both the 3ft test, and 30ft test I was focusing on a flat wall with no features (in full light, the camera can not focus on the wall, since there’s nothing there to focus on) and with the AF Assistant IR light, I can focus on the blank wall at 30ft away even with the side focusing points. Quite impressive.

Some internal details

Fig 3. LTC3490 LED driver in action

I have moved away from the 1 battery setup of the previous version. The LED is drawing up about 250mA (which is 10 times what the laser was using) so I figured I’d move up to 2 x AA cells.
I have also moved away from thru hole for most components. Surface mount technology is what I’ll be focusing on from now on.

The LED driver IC is a LTC3490. It can drive up to 350mA though  I cannot drive this LED that high. The LED module heats up too much for my comfort. At about 230-250mA it still gets warm but I can keep my finger on it indeterminately. Anything above that current and I can’t keep my finger on it for too long. There is a trimmer pot on the board so I can adjust the current to the LED but I may take it out in the production version.

So far all the tests are looking very positive. The other surface mount IC is a MAX4289 op-amp. It’s able to run on low voltage (down to 0.7V). Most other op-amps need at least 3 volts to run, which I may not have if I’m running two NiMH batteries at 1.2V a piece.

Fig 4. Fully populated board

I’ve only been playing with this setup for a couple of days, and will be testing it at music festival next weekend.

UPDATE:

I took some measurements of the wavelength of light from a couple of AF assist lights form Canon flashes. Read about them here.

Mechanically etching PCB boards

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Process to get PCB boards made.

– Design in Eagle, and export from the CAM module in Eagle layers 16, 17, 18, 20, as GERBER_RS274X
– Also export layers 44 and 45  as EXCELLON
– Import gerber file and excellon fine in CircuitCam
– Isolate as required (using only small and standard tools), and batch export DXF ;this outputs 4 files (small tool path DXF, Standard tool path DXF, Drill DXF and border DXF)
– Import DXF files in CNC USB Controller software, and export “Toolpath to G-code”
– Each DXF file will have a .nc file to be cut with the appropriate tool.

AF Assistant v3.2 development

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Work has been progressing on a newer version of the AF Assistant. The next incremental version (v3.2) will be made using surface mount components, and extra safety precautions have been added to protect the camera from any unwanted electrical signals.
Both inputs from the camera are isolated using buffers, and the ground is protected against reverse voltage.

Testing on this new design should start soon, and once complete all new AF Assistants will be built using this process.