l o a d i n g . . .
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22nd Jun 2014

The White House

This week has been pretty unbelievable: I was invited to the White House, to meet President Obama.  That's right.  The White House, the President of the United States of America.

In an official proclamation the President declared the 18th of June, 2014 to be the national Day of Making to encourage invention, innovation, and hopefully the economic growth and social benefits that these things bring.  To go along with this proclamation he hosted a very small Maker Faire at the White House.  A very limited number of guests were invited to present their projects to the President, and the Electric Giraffe was one of them.

The timing was incredibly tight - Lindz only found out 9 days prior to the event, and I only had 4 days!  Getting a ton of robotic giraffe from San Diego to Washington DC is no trivial matter, the farthest he has ever travelled before is San Francisco to the Bay Area Maker Faire.  Washington DC is over 2,500 from San Deigo, so a plan of action was required.  A shipping container was hastily ordered, the giraffe was bundled into it, and sent on its way on the back of a lorry across the entire width of the USA.

My journey began at 5am on Tuesday: I drove the two hours to the airport, arriving in plenty of time for my flight.  When I checked in they must have already allocated most of the seats as they put me in /premium/ economy - an extra 5 inches of leg room.  I looked it up, and this would normally have cost an extra $100!  I was very pleased to find out that the seat had its own power socket, so I plugged in my laptop and spent the next 8 hours watching Doctor Who while I crossed the Atlantic.  I arrived in Washington mid-afternoon.  Upon stepping out of the station I was hit by a wall of heat - it was 35 degrees (95 Fahrenheit) and 70% humidity, making the air feel thick and wet.  Upon talking to some other people, this was apparently extreme even for Washington.  Lindz took me to the Hilton Garden hotel where his dad Ron was already waiting, and we crashed for a couple of hours before meeting up with some of the Maker Faire folks that were also staying in the same hotel - Sherry, Dale, Louise and many more.  We had a great time and stayed up later than we probably should have given the early start we had to have the next morning...

After a night spent mostly trying to find a sleeping position where there wasn't a spring digging into my ribs (a fruitless pursuit) we rose at 5am to fetch the giraffe from its holding bay.  The giraffe had been delivered on time and in one piece to a holding warehouse owned by the Smithsonian museum.  The staff there had apparently been delighted by its arrival, and Lindz was more than happy to tell them all about it and send them home with some t-shirts.  We were very grateful to them for giving us a place to unload and store the giraffe.  We loaded the giraffe onto the back of a tow truck, and after some debate about low bridges we headed towards the White House.  The ride was extremely tense as we were stuck in traffic and very worried that we would miss the deadline for entering - we had phone calls along the way telling us to hurry up, but the traffic was solid and there was nothing we could do.  After a nail-biting 40 minutes or so we arrived at a small car park a little way away from the White House, where we were given a brief inspection by the security forces.  The police checked our ID and then a secret service agent arrived in a large SUV.  He gave the giraffe a very brief check and then escorted us to the White House entrance - flashing lights and all. We were even told to run red lights rather than be separated from our escort.  At the main entrance we had our ID checked again and the vehicles searched by a sniffer dog, then we were escorted through another security checkpoint, again having our credentials checked, to arrive on the main lawn of the White House.  Security was extremely tight, as you might imagine.  We had to be escorted by a guard at all times, and there were snipers on the roof keeping overwatch.  We hurridly set up the giraffe, reattaching the head and making sure everything worked before motoring up the hill and parking outside the rose garden, just to the side of the main entrance of the White House.

The giraffe attracted a lot of attention from the White House staff, all of them taking photos while Lindz explained about its operation.  The White House media staff strapped a small camera to the giraffe's neck which was used for live streaming the event.  Once everything was set up we had time to go inside the White House itself and view some of the other projects.  As you would expect, the White House was amazing on the inside, immaculately kept and filled with period artefacts.

Eventually word came that the president was on his way.  We took our post by the giraffe while all everybody else was cleared from the area.  With only a few minutes to go I was approached and told that there was a problem with my paperwork - I had somehow been overlooked, and did not have authorization to appear on camera with the president.  Apparently a more detailed background check has to be done if you are going to appear on camera next to him, someone had forgotten to do mine, and so I had to be escorted away to the holding area.  I was bitterly disappointed, as was Lindz.  After all the excitement of being told I was going to meet him, the very expensive flight across the Atlantic, all the fuss and tribulations of getting everything ready on time - to have my chance snatched away at the last moment was heartbreaking.  Nothing could be done about it, so I just had to go inside to sit and wait while Lindz spoke to the president on his own.  I didn't even find out what was said until I watched it on the news a day or two later.

I was sent to wait in the conference room where the president was to give his speech.  The staff seemed to like playing musical chairs - I was moved from my seat four times.  One of the people sitting next to me was moved five times.  I didn't really mind though because it was a long wait and the moving gave me a chance to talk to a variety of people.  I spoke to the gentleman from France that had brought a 3D printed rendition of the audio waveform of one of the president's speeches, and a lady who was turning libraries into maker spaces.  (Other folks I met included Bill Nye the Science Guy, the mayor of Rockford Illinois, the White House science advisor, and many more whom I fail to recall...)  My final seat put me in the front row, at the far right of the room.

The president's speech was engaging, although his joke about dropping the trailing 'e' from Maker Faire didn't seem to go down too well with the crowd.  He spoke of the importance of innovation to invigorate the manufacturing sector, and how new technology such as 3D printing was bringing the possibility of product design and prototyping to a wide audience.  I didn't know this at the time, but apparently it is traditional that the President shakes hands with the people in the front row of the audience following a speech.  Someone must have pulled some strings to place me there after the disappointment of being pulled out of the interview at the last moment, and so as soon as the speech was over the President came straight over to me, we said hello and shook hands.  It may have been a brief encounter, but still - I would never have imagined that one day I would be invited to the White House to meet the President of the United States of America.

Once the president departed all that remained for us was to pack up the giraffe and leave.  Security was tight even on exit - the guard at the gate had to phone his superiour just to allow us to leave! Tired and hungry, we made our way back to the hotel to meet up with the other makers for a meal.  On the way there we heard police sirens behind us and were rapidly overtaken by a fast moving convoy of police cars in the lead, then a large black vehicle with state flags on the bonnet, followed by a menacing black SUV at the rear.  This was very likely the president on his way to his next engagement.  The black SUV in the rear was very likely one of the special secret service vehicles which have a mechanism in the back that allows the roof to open and a minigun on a 360 degree track to pop up out of it.  We had a good dinner with our fellow makers, eventually heading to the W hotel and up to the very top floor, which contains an open air bar.  Despite it being around midnight it was still very hot, and in the humid air we got to watch a lightning show over Washington in the darkness.

The following day we had to fly home, however our flights were in the afternoon so we had the morning to ourselves.  We decided to walk over to the Smithsonian Air and Space museum, past the Washington Monument on the way.  The white stone needle sits at one end of a long park, opposite the Capitol building.  It was much larger than we expected - often when you are used to seeing a structure on television it can seem smaller when viewed in real life, but this was quite the opposite.  The Smithsonian was absolutely packed with priceless and unique artefacts - prototype aircraft, space capsules, satellites and rockets.  Every single corner contained something unique and intriguing - for anyone interested in aviation or space travel, it is definitely a place worth visiting.  We stayed as long as time would permit, then took a ride on a rickshaw back to the hotel to collect our things and then headed to the airport.  We said our goodbyes, still in disbelief at the events of the previous day, and parted ways.  My flight back was uneventful, although unfortunately Lindz and Ron had their flight cancelled due to bad weather at the destination.

Thus ended my trip to meet the 'leader of the free world', President Barack Obama.  In viewing the media coverage after the event it became clear that the giraffe had stolen the show, and we are very proud to have been given this opportunity and recognition.

04th Jun 2014

Maker Faire 2014

The Maker Faire 2014 has come to a close.  Although undoubtedly very busy, my month of work-like-hell preparations prior to the fair made this the least stressful event yet.
The big new feature for 2014 was a whole new set of hexagonal spots, along with brand new WS2812b smart LEDs, which of course necessitated a new driver board.  The smart LEDs are a great benefit to the project - they're bright, they mix the colours beautifully, and they slash the amount of wiring and control circuitry.  Using standard 5mm LEDs we had 5 controller boards networked to the main USB controller, each board having 4x40 pin PIC chips and two 64-way ribbon cables going out to all the little LED boards, each of which had 12 individual 5mm LEDs.  Now everything is driven directly from the USB controller, no extra boards are required.  The communication protocol is simple and efficient, although implementing 3 communication buses on a single 8-bit PIC at a decent framerate was a bit of a challenge. The new USB controller uses the same circuit board as the old one, thus saving some time and money.  Minimal modifications were required to the hardware, I simply needed to cut and jumper a few traces around.  This was helped by a design feature I requested when the circuit board was being designed: every I/O pin on the PIC chip has an empty hole next to it on the PCB.  This means that if I want to re-route it, I only need to cut the trace and solder a jumper wire into the unused hole.  The USB controller requires two PIC chips, as it's not possible to find one that has both a CAN and USB controller in a DIP package.  I did have them communicating over a parallel bus, but for the rebuild I modified it to SPI.  I rewrote all the firmware from scratch using the updated Microchip USB libraries.  The physical connections to the board remain the same - CAN, USB, and LED data - making it more or less a drop-in replacement.  Due to the modular nature of the software I wrote, it's even possible to have multiple boards connected at the same time, even mixing boards of different versions.  This proved to be very useful, as we did not have time to replace all the LEDs in the head so that continued to use an old USB board and LED controller board. The one flaw with the LEDs is that they seem to be rather easy to blow up.  The first panel of spots had been running in the house for a couple of weeks, but when we mounted it on to the giraffe it immediately fried, several of the LEDs blowing up.  We investigated as best we could, and came to the conclusion that it was probably due to static electricity.  To protect against this, we took several measures:
  1. We wrapped the LEDs in transparent heat-shrink tubing (only shrunk at the ends) to provide a physical barrier
  2. We added a grounding strap between the panel frame and the giraffe frame
  3. We added protection filters with a sacrificial LED at the start of each chain of LEDs
The filter circuit was a simple design:
Capacitor C2 is simply to smooth out ripple on the power supply.  Next comes a low pass filter made with R1 and C1, which should help to remove high frequency noise from the data line.  Finally, the two diodes clamp the data line between the supply rails.  I'm not specifying component values here because I would like to refine them further. Since making these changes, we haven't had any LEDs blow up.  It's hard to say exactly which change was the one that solved the problem, but I'm going to guess that it was enclosing them in tubing to physically isolate them from any static zaps. There were a few small dramas prior to the show - notably the battery charger catching fire and Lindz almost losing an eye when a scalpel went flying past his face, but we managed to make it there with both us and the giraffe in one piece.  Thanks to Lindz's new car (aka "the beast") the drive up there was more pleasant - no overheating engine and far fewer fuel stops.  The traffic in LA and San Mateo cost us a couple of hours, but all in all it was pretty smooth. The show itself went pretty much without a hitch.  There was much to see and much to do, the cat-herding of interviews being organized, the technical discussions and the general "ooh"s and "aah"s of the event.
I spoke to both Microchip and Texas Instruments - I want the next iteration of hardware to use 32-bit chips (which means finally taking the plunge into surface mount), and using PICs will require a new toolchain anyway as the ICD2 is not supported any more, so now is a good time to look at switching platform.  It's hard to choose, at the moment - I'm not a big fan of the Arduino style boards that are so popular at the moment because although having a pre-made PCB is attractive, if you want to add extra hardware then you need to have a PCB printed for the shield anyway, so it doesn't seem to save you anything other than in the earliest stage of prototyping. A couple of highlights of the show were El Pulpo Mechanico, the giant flaming octopus; and the hydraulic snake, an enormous segmented hydraulic snake. The giraffe was also chosen as this year's "learn to solder" project!
25th Nov 2013


I'm feeling a bit stupid at the moment - yesterday I had my first mains electric shock (230 Volts over here).
I was installing a new light fitting and I was in a rush because I had to go out.  Yep, rushing isn't clever.  I normally turn off both the lighting the sockets, and I normally test the terminals with a screwdriver before touching, but because I was in a hurry I skipped these.  I started splicing into the junction box... neutral ok, earth ok, live - ouch!  It was a junction box for the sockets, not the lights - I'd misidentified it.  Stupid zebra.

That said, it didn't hurt as much as I expected, and I didn't fall off the ladder.   I didn't even swear, although I did let out an "aargh!"  :P
19th Oct 2013

Manchester Furmeet

I went to my first Manchester Furmeet at the weekend, along with Chris Horsie and Taisenki.  It was good fun!

We took the train to Manchester and arrived just before noon, easily spotting a group of about 20 furries gathered in the station.  We made some brief introductions and headed to the bar that was the base for the meet.  I think there were around 50 attendees in total - more than I expected.  I put my fursuit on and wandered for a bit, then we met Stuart Otterson, the meet organizer.  He was surprised that none of us had ever been to Manchester before, so he kindly offered to give us a tour.  The four of us had a good wander around many of the shops in the city centre (me still in fursuit of course).  We even met a couple of bronies on the street - one wearing a Rainbow Dash cutie mark patch on his shirt and one wearing a Rarity cap.  I was wearing my Fluttershy t-shirt!

We finished the tour of the city just in time for the beginning of the fursuit walk, so I was straight back out on another walk around town!  All in all I guess I spent about 3 hours fursuiting around the city, which was lots of fun.  The only downside was that due to being in fursuit all the time, I didn't really talk to anyone while I was there.  There's another meet at the end of next month, I haven't decided if I'll go there yet, we'll see!
29th Aug 2013

Dog Sick Slime Mould

I went for a walk in the field and found this strange deposit clinging half way up some blades of grass.  The picture says it all - a strange white cellular substance, with open cells rather than bubbles like you'd get with cuckoo spit.  It was wet to the touch.  I took a photo and asked my friend Chiron for assistance in identifying it.  Although he had also never seen anything like it, he quickly found out that it is a slime mould - specifically "dog sick slime mould".  Well I never.
01st Aug 2013

New Fursuit Tail

I made myself a new fursuit tail!
It's basically the same as the old one, except I removed the curve from the top because that made it stick out too far. The big difference is that this one is sewn together whereas the first one I made had the fur glued onto a foam core.
I didn't really think I'd be able to sew it, but I did, so I am quite pleased that it was successful. I tried to strengthen the construction by adding an inner lining of material, and a strip of webbing that runs the entire length of the tail and forms the belt loop - hopefully this will keep it in one piece if some ill-behaved child pulls on it.
21st Jul 2013

Zebra Herd Meeting 2013

Our little UK zebra herd had its second meeting this week as Squally, Chiron, and Chiron's bf Wuffle (non-zebra!) came to visit me.

They all arrived on the same train at Bangor station, and I just managed to squeeze them and their luggage into my little car.  It was about 6pm, so after unloading our gear we went out for a Chinese takeaway.  We got a portion of inoffensive noodles for Squally to try, but unfortunately he's a very picky eater and wouldn't eat it - only a portion of chips.  The evening was still young when we finished, so I suggested a ride to the beach.  We drove over to Traeth Bychan and clambered around on the rocks until it got dark.  Chiron is the science zebra, and very interested in geology and biology.  We located some interesting rocks, including some very large chunks of fossilized coral.

We began Tuesday with a tour of the south-east corner of the island.  We started with Din Lligwy: an old abandoned chapel with a solid stone font and small crypt, some roman remains, and a very impressive 5,000 year old burial chamber.  We thoroughly poked and prodded around all of these sites, then followed the coast south, past the iron age hill fort King Arthur's Seat (we didn't stop because there isn't much to see there) and on to Penmon.  There is a ruined priory there, but for me the main attraction is the medieval dovecote - a magnificent stone structure with hundreds of nesting holes for birds.  It's also the site of the holy St. Seriol's well.

It was coming up to lunchtime, so we continued around the coast to Beaumaris in the hopes of finding a sandwich.  We investigated the castle, although didn't pay to enter, and had a walk along the main street and the promenade before acquiring some sandwiches (chicken tikka!) and sitting on the sea wall to eat.  Even there we found a point of interest - the stone on which I sat contained a large fossilized coral.

After eating we backtracked along the coast to Caim, a tiny town and not the easiest place to find.  We had a walk across the fields and along the rocky shoreline, although it was steep and difficult to access.  The field was full of bright red cinnabar moths.

We then drove onward to Bryn Celli Ddu, an impressive prehistoric burial mound, then continued on for a quick stop at Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch (I can pronounce it, but I can't spell it yet...) to have our photos taken in front of the sign.

We headed for home, making a stop at the supermarket to pick up some supplies - Chiron and Wuffle cooked four different curries for our enjoyment!  Tarka dahl, bombay aloo, a chicken pasander, and a beef jalfrezi.  They were delicious, but unfortunately just the smell of them made Squally feel ill, so we had to throw in some chips for him.

With the day almost over, we headed back outside and lit a small bonfire.  We burnt some leylandii that I'd trimmed the previous week, and kept it fed until about 1am (even cutting down some gorse just to keep the fire going).  The sky was clear and many stars were visible due to the reduced light pollution out here - we even spotted a shooting star or two.

On Wednesday we made for the north-west of the island - the South Stack lighthouse and nature reserve.  We looked at the impressive folded geology, the variety of plant and bird life, and also the large group of iron age hut circles.  We had a picnic lunch overlooking the sea, and then headed towards the abandoned copper mine at Parys Mountain.  Once the primary copper exporter of the world, the "mountain" is now a barren pit of broken rocks.  It is well worth a visit - the colours are striking due to the amount of iron in the rocks, and we spent a long time smashing open rocks to see what we could find inside.  They are rich with metals, tiny cubes of silver and gold.  The site itself is great for pronking, and I spent a lot of time just bouncing between rocks.

In the evening, Chiron and Wuffle made Chinese food - sweet and sour, my favourite.  After that we got an old microwave oven and microwaved whatever we could find until the microwave finally blew up.  We nuked one of the rocks we'd collected and actually managed to set it on fire!  The inside of the rock glowed red and small blue flames burnt on the surface, even after taking it out of the microwave.  We also microwaved a dead sparrow, which reeked.  Don't do that.

Thursday was our last full day, and we made for Snowdonia.  The plan was to walk from Llyn Ogwen to the Devil's Kitchen. Unfortunately the route proved too much for my companions (it turns out that Wuffle is not very confident at altitude), however the route I'd chosen took this eventuality into account, so it wasn't an inconvenience - we just skipped that part and carried on around the lake.  Again, I did a lot of pronking on the rocks while the others were walking.

Our last activity was a fursuit outing, for which we returned to Beaumaris.  We only spent about 30 minutes, but it was a nice outing nonetheless.  It was Chiron's first outing, and his self-made suit looked great!  The reactions from the public could have been a little better though.

On Friday morning it was sadly time for all to depart - herd meeting over.  I hope they will come back soon!
I've been designing a very simple new circuit to control the servos in the forthcoming new neck.

Each joint calls for a two channel servo driver, and I decided to add current sensing capability to this.  By continuously monitoring the current drawn by the motor, the circuit should be able detect the increase in current that occurs when the motor is stalled - because the neck has hit an obstruction or the mechanism has jammed - and shut down the servo drive before too much damage is done.

The circuit is split into three parts: Firstly, a current sensing resistor; second, a low-pass filter; thirdly, an amplifier.  The output from this is then fed into a standard CAN (Controller Area Network) circuit driven by a PIC chip.

The principle of measuring current with a current sense resistor is very simple: you put a low-value resistor in series with the power supply, and measure the voltage across it.  The resistor can be placed either at the power supply's positive terminal ("high-side"), or negative terminal ("low-side").  Using the low side is slightly simpler as one end of the resistor is grounded.  It has some disadvantages (the ground voltage level for the circuit being sensed is raised up by the voltage across the resistor, and it cannot measure if the load is shorted to ground), however those aren't a problem for this application.

The current flowing through the motor passes through the current sense resistor, developing a small voltage of V = IR.  I have estimated the maximum servo current to be 5A (this will be confirmed when I get the actual servo specifications).  With a resistance of 0.05 ohms, this will give a voltage range of 0 - 0.25V for a current of 0 - 5A.

The power rating of the resistor is important here.  Power is calculated as P = I2R, so at 5A this would give me a power rating of 5*5*0.05 = 1.25W.  This is the minimum wattage for the current sense resistor.

Before being amplified, the signal passes through a 7Hz low-pass RC filter.  This is simply a 220 ohm resistor and a 100uF capacitor arranged so as to block any high frequency noise that may be present on the sensor, for example voltage spikes caused by the servo motor's operation.  The motor will only need to be sampled a few times per second, so I chose 7Hz as the cut-off frequency for the filter to avoid any aliasing effects when sampling.  Aliasing occurs when signals are sampled more slowly than half their maximum frequency component, and causes the high frequencies to appear as if they were low frequency changes, giving you an erroneous result.

The next stage is a non-inverting amplifier.  An amplifier is necessary here because the chip's analogue to digital converter is not especially precise, so amplifying the signal from 0 - 0.25V into the range 0 - 2.5V allows me to use more of its range, giving a more precise current measurement.

Because the amplifier output needs to operate down to zero volts, I chose the LM358 dual operational amplifier.  This 8-pin IC contains two amplifiers with an output swing of 0V to Vcc -1.5V.  Normal amplifiers cannot drive their output to the power rails, so a "rail to rail" amplifier is needed for an application like this - however in this instance I only need to include the 0V rail, so the LM358 will do the job just fine.

The two feedback resistors are arranged to give me an amplifier gain of 10.

Finally, the signal passes through a 20 ohm resistor before being fed into the PIC chip's analogue to digital converter.  The 20 ohm resistor is recommended to ensure the amplifier remains stable when driving a capacitive load.
29th Jun 2013

Saw Blade Clock

I had an old and rusted circular saw blade lying around, so I turned it into a clock!
The movement was only £2 from eBay, plus one large washer in the middle to hold it together.

25th Jun 2013

The illusion of safety

I bought some LED floodlights, and before I put them up I cracked them open - partly out of curiosity and partly to seal the joints with silicone sealant to help keep the rain out.  One thing jumped out at me when I opened them though...

These are in metal cases, so that earth wire really should be connected.  I bought three and they are all the same, so it wasn't a manufacturing mistake.  Ah well.  I got them installed without any problem, although it took ages and entire box of twin and earth clips.  They work really well.  They're only 10 Watts so they're not very bright, but they're enough to get me to the back door at night.