GCS v2

It’s come a long way.  Full physical prototype, new electronics, new PCBs!  Deviating from the original prototype, here are the alterations:

  • Stepper motors instead of servos.  My servos from HobbyKing arrived while I was on vacation…and were returned to sender.  Instead of waiting 6 weeks for them to be returned and then another 6 weeks to be shipped back I just canceled the order.  I was worried about the response time and noise factors as well.  Instead i opted for 400-step 68 0z-in stepper motors from Sparkfun.  These sport 0.9 degrees per step, and can be microstepped to 1/32 of a step with this low-voltage stepper driver from Pololu.  With incredible resolution, the motors draw a lot of power (up to 1.7A each) and weigh quite a bit compared to servos.  I ordered breakouts for testing in the PCB stack below and incorporated the drivers in the new PCBs.  The control scheme is also much simpler!  Only two pins per motor!
  • New PCB.  Incorporating the stepper drivers was necessary, and they need heatsinking to sustain peak currents on the stepper motors, so I increased the PCB size to accommodate.  I’ll need to find some small heatsinks for the driver ICs.  The other major change was separating the IMU sensors from the rest of the board: they are meant to attach to the camera via hotshoe and have a tether back to the main PCB.  The sensor board can be seen in the lower left of the photos and lower right of the schematic, it’s super tiny and meant to be cut off after prototyping.  Also, I was able to remove the 5v regulator and transistors to reduce component complexity.  The last change was to slim down the PCB to fit on the back of the frame.
  • Laser cut baltic birch frame!  I drew up designs for the new stepper motors with added bracing and had them laser cut at StudentRND.  The whole thing slotted together like a 3D puzzle and all the motors fit perfectly.  The hoop arch is for supporting the overhanging weight of the camera (tested to 10 pounds!) and rolls smoothly on 2 shielded bearings and ultra low friction tape.  It’s large enough to support all DSLR/M43 cameras, even the RED Epic and Sony FS700.  All hardware is M6 Allen-head bolts with nuts super-glued in place and M3 for the motor mounts.  Go metric.

Already I want to move the top (pan/yaw) motor back another 2 inches or so, the weight of the roll motor and battery create a back-heavy frame, adding a camera would then need to offset that weight as well.  So far I’ve got two motors twitching but there are some power issues to sort out.

Posted in Blog, Gyro Stabilizer, Projects | Leave a comment

NHD Documentary

Mentioned in a few other posts, but below is my winning documentary for National History Day 2013.  We placed first in the nation for senior group documentary after competing at University of Maryland this June.  It took my team and I several hundred hours of hard work but it paid off!

Posted in Blog | Leave a comment

Homemade Lightning

This post has been sitting as a draft until I got around taking pictures.  The actual coil was completed in March of 2013.

In light of my participation in National History Day, I took the opportunity to have the topic of Nikola Tesla’s AC Power Grid for this year’s theme (turning points in history).  Tesla is also the conjurer of lightning by way of his Tesla coil, something I’ve wanted to build for a few years now and had designs drawn up, the math figured out all in my head just waiting for the time (and funds) do start building.  Early 2013 presented itself nicely.

My birthday present.  Twin 12kv 60ma Franceformers.

My birthday present. Twin 12kv 60ma Franceformers.

  • 12kv 60ma Franceformer neon sign transformers for the HV source.   I bought two of them via Craigslist, matching, and put them in parallel to get extra current and spark length (120ma @ 12000v = 1440 watts = 60″ of theoretical spark length).

 

  • 26kv 26.25nf MMC capacitor bank.  Composed 6.5kv 0.015uf polypropylene caps I (bought from Alltronics).  28 caps arranged into series strings of 4, 7 strings in parallel.  Surplus made this a relatively cheap solution!  However, this is close to the minimum capacitor value I calculated.  Additional parallel strings will be added in the future to increase power.  Each capacitor has a 1M 1/2 watt resistor to bleed the current quickly after a run.  THe whole assembly is loosely shoved into a schedule 20 PVC tube, hot glued at the ends, and then zip-tied to the base.

 

  • 7mm vacuum-qenched spark gap.  Copper pipes arranged across from each other, plumbed with PVC to a vacuum to suck air through them to reduce heating.  The cables are bolted directly to the pipe fittings.

 

  • Primary coil.  1/4″ copper tubing, 12 turns spaced 1/4″ apart.  This is about 40 feet of copper refrigeration tubing on 1/2″ tall HDPE mounts.  The mounts were constructed by drilling 1/4″ holes in the center of 1″ wide strips, then cutting down the center of the holes – yielding 1/2″ square bars with semicircle indentations for the tubing to rest into.  192 zip ties secure all the tubing into a tight spiral.

 

Strike rail tap to protect primary from strikes.

Strike rail tap to protect primary from strikes.

  • Strike Rail.  2″ above the primary resides an earth-grounded loop of copper tubing to prevent arcs to the primary and blow the NSTs.  Not a continuous loop to avoid efficiency loss via induction.

 

  • Secondary.  ~1800 feet of 23 gauge magnet wire.  900 turns around 6″ PVC drain pipe.  This has an outside diameter of 6 7/16″ and a wind length of 28″.  the ends are about 8 inches in lead, wrapped in 4″ Kapton tape to prevent unwinding.

 

  • Top load.  6″ dryer duct around 12″ pie pans, 24″ in diameter and the whole thing wrapped over with a few layers of aluminum tape to make it super smooth and hold the most charge.  A single breakout point made of a thumbtack allows for long arcs.  Fastened to the secondary with a bolt in the center.  This will likely be the first upgrade to increase the spark length.

 

  • Secondary mount.  A 6″ endcap is held below the primary MDF platform with wood blocks. This allows for adjustable K-factor, or how tightly coupled the primary and secondary are by using spacers in the bottom of the cap. A bolt in the center provides a tap point.

 

  • Wiring and control box.  All wiring is 10 gauge jumper cables with appropriately size crimp rings.  The 10-gauge extension cord leads back to a metal box with two 20 amp breakers (only one used)

Performance: About 4-5 feet of spark!  The coil is super loud to the disappointment of my  neighbors and you can really smell the ozone.  It’s able to light fluorescent tubes wirelessly from about 15 feet away.

Posted in Blog, Projects, Tesla Coil | 3 Comments

Gyroscopic Camera Stabilizer

Been quite some time since my last post and I’ve started a few more projects.  The death of LENSE 2 brought on the end of two projects at once – the equipment never being found also meant my MicroQuad board and all the components are missing as well.  Until I can afford to pony up and buy all those sensors again, I decided to take a break and build myself a Tesla Coil.  More on that later though.

Fast forward to mid April, past VEX robotics, FIRST competitions, and before finals I stumbled upon Vincent Laforet’s blog and his camera work.  The post currently on the front page: The $15,000 Freefly MOVI.

The MOVI is essentially a three axis camera gimbal that uses a gyroscope to measure camera shake from the operator, then rotates the camera in the opposite direction to negate all the camera shake and result in a completely steady shot.  It also has the ability to be controlled wirelessly by a second operator, is completely silent, and weighs under 3.5 pounds while supporting a 10 pound camera.  The results were absolutely astounding!  My first thought was that this would be an awesome tool in the hands of some indie film makers and really open doors to the complexity of shots they can do with fewer tools.  But it does cost $15,000.

My first thought after watching the video was that this is the same technology used by multicopters to stabilize their aerial cameras, and those don’t cost nearly as much.  So I had a new project – design and build myself a gyroscopic camera stabilizer offering 90% of the  functionality as the Freefly MOVI but for under 4% of the cost.

Design Requirements:

  • Under $600.  Near the price of a Glidecam 4000, for example.
  • Support popular amateur film cameras.  The Canon 5D MK I/II/III, Canon 7D, Panasonic GH2/GH3, Blackmagic Cinema Camera seem to be all the rage and what a lot of my favorite indie film makers are using to create absolutely incredible artwork.
  • Stabilize up to 8 pounds of camera and lens.  Ballpark figure for a 5lb RED epic plus a lighter lens, or a 5D and most lenses Canon makes.
  • 4 hour minimum battery life.  No time to charge batteries while shooting, probably easiest to swap out batteries during the day than have one massive battery though.
  • Under 3.5 pounds.  As light as possible allows the operator and film maker to use it all day all shoot long without getting tired.
  • Adjustable for the camera/lens combination. It is essential to have the center of gravity of the camera/lens centered with the rotation axis to maximize performance.
  • Quiet, as near to silent operation as possible.  In my mind most shots you would use the stabilizer for wouldn’t be scenes for dialogue, but there is no need for loud gear.
  • Easy to use user interface with settings and memory modes.  A simple menu system and screen, with variable levels of stabilization in each axis for a shaky-cam effect or isolating one axis that can be saved and recalled depending on the effect, shot, scene, or camera.
  • Easy to obtain, maintain, and replace parts.  One of the goals is to make this system open source and easily built buy anyone with freely available parts, easy to be fixed in the field and not reliant on specialized patented technology.  This means using hobby servos instead of custom actuators, laser cut plywood instead of carbon fiber, etc.  Maintenance must be kept to a minumum, meaning few moving parts and very robust mechanics.  Should something break, it should be easy and quick to buy and replace.
  • Opportunity for expansion.  The addition of follow focus, iris control, and of course remote control support should be designed into the system.

My first steps were to figure out the physical requirements of the device – how strong are the motors? How fast does it need to move? How big is the entire system?  I started with the Canon 5D and made some rough size assumptions to get a sense of scale and built a tiny balsa model of the mechanism.  From the size assumptions I made and the projected 8 pound capacity, the next step was to figure out how much torque was needed to move the payload.  Wikipedia to the rescue.

After a bit of research, I determined that the device is most efficient when the payload mass is centered around the axes of rotation.  This way, it requires minimal torque to accelerate the mass and becomes a problem of inertia.  Wikipedia articles and a few questions to my physics teacher helped me calculate the torque required to accelerate an 8 pound cylinder from rest to a speed of 60 degrees/0.12 seconds about the center of mass.  That speed is merely a common speed for high torque hobby servos.  This resulting torque was then converted from newton-meters to kiliogram-centimeters used to rank servo torque, then tripled.  With my speed and torque requirements I set out to find the ideal servo.  To maintain the precision and long life requirements, I also decided to use a “high voltage” 7.4v servo, digital instead of analog, with titanium gears and ball bearings for maximum rigidity.  Hobbyking led me to the Turnigy 1268HV, everything I needed for just $35 courtesy of Chinese manufacturing.

For the rest of the mechanics, the carbon fiber construction of the MOVI is awesome but entirely out my capabilities and the price range.  I decided to go with 6mm baltic birch plywood, laser cut box joints and glue together with mounting points for the motors.  This stuff is rigid, looks sharp when laser cut, and is super cheap and simple to work with.  This has the benefit of keeping a low cost should you need to order a complete replacement.

On to electronics.  Rather than go through the design process, these are my final components:

  • PIC32MX150F128B microcontroller (Microchip)  In a 44 pin TQFP, I can still solder and maintain just enough IO for all the components, with more than enough horsepower to update the servos at 50Hz or so.  It also has several SPI, serial, and I2C busses, and 4 PWM outputs for servos.  Having all the pins remappable also simplifies PCB routing immensely.
  • L3G4200D 3-axis gyroscope (STMicro)  Tons of examples and support, variable sensitivity, and high speed 800Hz updates on the SPI bus.
  • 25AA320A 32k EEPROM (Microchip)  More than enough memory for any number of user settings, SPI communication.
  • RN-41 Bluetooth module (Roving Networks)  Class 1 power output – up to 100m of range and provides expansion for wireless control.  Coincidentally, Microchip controller inside this radio, RS232 communication with the PIC32.
  • NHD-C160100DiZ-FSM-FBW display (Newhaven)  A simple 160×100 chip-on-glass LCD display with a white backlight and I2C communication.  I’ve used these before, they are inexpensive, small, and have great contrast.
  • REG102GA-3.3 and MIC5205  A 10-3.3v converter for the electronics, and a 5v converter to bump up the singal level to the servos.  I’m pretty sure the servo electronics are 5V logic, but unsure if 3.3v PWM signals will interface properly.  The PWM outputs go through N-channel MOSFETs that switch the 5v signal.
  • Expansion headers  I plan to use a button array as a joystick, so there’s a 5 pin header for that and an additional 4 pin header for any additional control buttons I might add later.  There are also 4 PWM outputs and a connector for the LCD backlight.
  • 7.4v 6000mah LiPo Battery (Tenergy)  The servos are rated at 400ma current draw each, so worst case I’ll get 5 hours or so of run time.  Inexpensive and lightweight, as well as offering a bit of mass for helping center the camera mass.

After some adventures in the land of eagle part creation and rerouting the board several times I sent the gerbers to OSH Park.  Two weeks later three purple and gold boards arrived and I began assembly.  It was a real challenge learning to solder the 1mm pitch JST-SH connectors, but after a few tries everything went smoothly.  Nothing was shorted out so I powered up the board and the LCD backlight lit up, good sign.  Not for long though.  I don’t remember exactly what happened but I the regulator was being held in shutdown mode and the solution was to disconnect the “no connect” pin from ground.  I don’t know why I tied it there anyway…but in the process of lifting it I managed to destroy a bit of the solder mask and render the power circuitry useless, visible below in the photos.  The only solution was to solder up another PCB, good thing OSH sends you three!  I was more than happy to have my hot air station to remove all the ICs and connectors, that tool has probably paid for itself in ICs and PCBs alone.

You might notice the unpopulated radio footprint, I held off on ordering those until I got the rest of the circuit working.  In my experience those large packages are extremely difficult to rework anyway.  So far in the project I’m about ready to get working on the software (the reworked board does power up and connect to the debugger!) and once the servos arrive I can complete the design files to have the plywood laser cut at StudentRND.  The battery and charger, mechanical parts from Mcmaster Carr, all the electronics, and Plywood are all sitting idle while the servos are on the slow boat from China.  I just aboslutely adore shipping times.

Size comparison of all the electronics.

Size comparison of all the electronics.

Bad white balance.  The LCD connected to the controller.

Bad white balance. The LCD connected to the controller.

For size comparison and finalposition of the parts.

For size comparison and finalposition of the parts.

DSC_9374 resize

First try on the bottom, second success on the top.

First try on the bottom, second success on the top.

Completely assembled after rework.

Completely assembled after rework.

The first PCB from OSH Park that I soldered up.

The first PCB from OSH Park that I soldered up.

 

Posted in Blog, Gyro Stabilizer, Projects | 5 Comments

LENSE, MicroQuad and New Projects

Skipping right to the big topic – LENSE is still out there somewhere.  I haven’t gotten any responses from any radio stations to my perpetual emails…however as soon as i can (within the next few weeks?) i’m going to try and drive out to Toppenish and look around.  For now i’m very busy working on an exciting VEX robotics team 917K and Team Top Gun for FIRST Robotics.  My microquad project will continue as soon as LENSE is wrapped up – i’m putting off having to purchase $150 of sensors again (they shared the same components and PCB).  There is also a definite Tesla coil in my future – maybe a 3000-lb electromagnet as well!

Posted in Blog, LENSE, MicroQuad, Projects | Leave a comment

T+12 hours. Bad News.

Payload missing.  12 hours since launch.  All set to go at 8:50 at Quincy, Washington when the SPOT II satellite beacon wouldn’t update it’s position on the website.  I cracked open the payload to find it claimed to have sent the message already – 30 minute delay on the SPOT website.  With that, I finished buttoning it up, and we released at 9:05.

Two more data points at 9:17 and 9:28, then no more.  At this point at 5 m/s ascent rate it would be above 20,000 feet – known limit of the SPOT from LENSEv1 last summer.  We hurriedly drove to Toppenish, Washington to the south, predicted landing zone.  About 10:50 was the predicted burst time – we stopped for lunch and I set up the helical and started sweeping the general direction of the payload for a 900mhz signal – no dice.

At 11:30 the payload should be under 20,000 feet – no SPOT updates.  we waited until 1:00 for any updates, nothing.  No luck with scanning the horizon with the 900mhz radio either.

At this point, the payload is likely within 5-10 miles of Toppenish, Washington.  The SPOT stops transmitting tracking data after 24 hours, assuming it is still working.  My optimistic theory is that there is an issue with the SPOT website (thus the lag of GPS point updates).  Phone lines aren’t open until Monday.

In the mean time I’m sending emails to radio stations to try and get the word out.  My number is written on the box and parachute – 425-829-4151 PLEASE call if you find a small pink box and red parachute with camera lens sticking out!

Posted in Blog, LENSE, Projects | Leave a comment

T-12 Hours.

12 hours to launch time of 10 AM in Quincy, Washington of LENSEv2.  Currently I’ve been troubleshooting for 12 hours and just patched up the electronics:

  • Adafruit Ultimate GPS v2  and v3
  • Copernicus II GPS
  • 2 Bubble Technology Neutron Dosimeters
  • Sparkfun heating pads
  • Canon SX210IS running a 8 second CHDK intervalometer script
  • EasyRadio Advanced 900 TRS transmitting GPS data out a cloverleaf antenna
  • 7 Energizer Ultimate Lithium batteries
  • SFE OpenLog data logger
  • Satellite SPOT II personal tracker
  • And a blinky LED.

Temperature sensors and barometric pressure sensors failed.  Tomorrow I’ll attempt to track the payload in real time with a heading/inclination script i coded to direct me where to point my 30dbi helical antenna, receiving real time GPS data.  On 1mw of transmit power from 50 miles…fat chance but I thought I’d try it.  Updates on @BudgetEngineer (twitter), I’ll be on the Adafruit Show and Tell tomorrow night to share the results.

Damn Murphy.  Long post and photos will follow.

Posted in Blog | Leave a comment