Archive for November, 2006

Tiger Flight

Saturday, November 25th, 2006

I’ve had my Tiger 50 for a while now, but haven’t managed to get any decent video, until now.  This was shot by a friend of mine this afternoon.

Video: Tiger 50 flight (WMV, 29mb)

We have liftoff - Part 2

Saturday, November 25th, 2006

So I’ve now had a little more time to fly this thing, and have sort of gotten the hang of it.  I took the Spyder prototype out to a field I fly my big helis at and got my friend Brady to shoot some footage.  The wind was blowing pretty good, so I was nervous, but decided I’ve give it a shot.

Video: Spyder prototype flight test #2. (WMV - 23Mb)

So now I’m working on the non-hovering flight part.  For this I need wings.  Hmmm…  Where’s my saw?

We have liftoff

Thursday, November 23rd, 2006

So it’s still rough, but I got most of my code moved over to the new chip.  I haven’t got the motor servos on yet, so there’s a chunk of code that mixes rudder into the speed controls to torque the thing into a spin.  It seems to work, though the torque effect is pretty small.

Check it out: first video. (WMV, 2.5mb)

I had just gotten the code finished, and it was starting to get dark.  I wanted at least one flight attempt in, and didn’t have much time to tweak it.  It didn’t land well, though nothing serious happened.

Here’s a shot of the current setup (the heli canopy is for orientation) and a close up of the main board.

More as it happens.

Electronics = pain

Wednesday, November 22nd, 2006

Well, at least for me it does.  I’m a software guy, and I’m sure there are things that every electronics guy with at least 4 brain cells remembers in his sleep that I’ve never heard of.  Things like ‘decoupling your power supply’.  That one cost me a few days, and a dead chip.

It’s all better now though - I’m learning pretty quickly, and have my new chip on a new board with some support crap, including a little LED display, a button, a knob, and a place to hook servos up.  I’ve got it reading my R/C receiver output with ~10 bit resolution, and I can produce the exact same output signals.  I wrote code to produce servo outputs in pairs, so each servo costs a max of 1ms.  This is handy when you’re controlling 14 of them, and your R/C receiver takes (worst case) 12ms to give you 6 signals.

I’m still over my 25ms budget - Just barely, granted, but enough to be worried.  See, servos need to hear from you about 40 times a second to keep them happy, which is 25ms between pulses.  My plan for the final version is to output all servo signals more or less at once.  It’ll be a bit of work, but I think I can do it.

I also bought some crap at Home Depot and made metal frame with landing gear.  I still have to make a place to put the electronics, but I’m not too worried about that.  The landing gear have a little spring to them, and the whole thing is screwed together, so it should be much more sturdy than my balsa version.

I have to write a little bit more support code, and then I hook up the gyros again.  Yeehaw.

New Toys

Saturday, November 18th, 2006

My new chips, resonators, and other bits have arrived, and I’ve started wiring it all up.  It’s not much to look at, but it’s a cool unit.  I bought a handful of 20MHz resonators to use with the new chips.  At 4 clocks per instruction, that’s 5 million instructions per second.

Turns out these chips have a thing called a PLL (Phase Locked Loop) inside them, which multiply your clock by 4.  The chip is rated up to 48MHz, so with the PLL enabled, and a ‘divide by 5′ in the oscillator settings, I’m running a full 12 million instructions per second.

The sad part is: At this point, all that power is being used to blink a pair of LEDs.

You gotta start somewhere.  As I said, it’s not much, but I’ve got the in-circuit programming interface done, so I can leave the chip in place to program it.  I also managed not to burn anything while soldering it all into place, which is a new ability.

Hopefully soon it’ll do more than just blink.

The Spyder Crawls…

Wednesday, November 8th, 2006

On Monday all of my motors and motor controllers arrived, so I went out and bought some balsa & basswood and worked up a really simple frame to put things on.

Then I wired up one of the controllers to find the rotation direction of the motors, plugged the battery in the wrong way, and heard a fairly loud, brief, pop.  A little smoke rolled out from behind the shrink-wrap, and I swear I heard it whimper.  This was around 3am, and was the most compelling evidence up to this point that I really needed to go to bed.  (Right after I ordered another motor controller)

Today I wired up two of the remaining controllers to the brain, and wrote the code to mix the aileron and elevator channles into the motor thrusts when hovering.  It went so quickly it was almost a letdown.  I’ve now successfully hovered (and steered) the rear half.

I think the only piece of the puzzle that’s left (and it’s a big piece) is adding in the gyro contributions.  I already have valid readings from them, it’s just going to be a matter of keeping track of how fast I’m moving and in which direction, deciding where I actually think I should be, and feeding the difference into the aileron and elevator inputs.  Sounds simple enough, right?

Dual axis gyro = fun

Saturday, November 4th, 2006

So I’m sure your average person would think I’m nuts, but I’m like a kid at Christmas when I open a box to find little electronic bits have arrived.  Today it was a dual-axis gyro sensor from SparkFun.  They sell all kinds of electronic gizmos, including this one, suggested to me by a guy at Overview Technologies.  They built a 4-prop camera platform and stabilized it with off-the-shelf R/C gyros, which work, but they’re not ideally suited for this kind of thing.  He said they were experimenting with this board from SparkFun, which has two gyros on it, and a bunch of pinouts to plug it directly into a PIC chip’s analog to digital converter.

It’s also really small.

They display it on the site next to a quarter, but it’s enlarged in the picture and I didn’t really register how small it was until I pulled it out of the package.  It’s just shy of a 3/4″ square.  The actual chip that’s doing all the work is about a ninth of that, but I’m not really comfortable with surface mount stuff, so the little board is perfect.

Tonight I wired up the gyro board and all the servo jacks on a small project board.  I can display the gyro values on the LEDs, so it appears to work.

My motors, speed controls, and counter-rotating propellers should all be here monday (Tues at the latest) so I’m chomping at the bit to get started with the meat of the project.


Bizarre Flying Machine

Saturday, November 4th, 2006

Recently, I bought an Expansion Pack for RealFlight G3 (see Learning to Fly).  It contained a lot of cardboard along with a couple new flying fields, and some aircraft.  Included among them was a Bizarre Flying Machine called the ‘Wolf Spyder’.  It has four propellers that move, and flies a bit like a harrier.  They posted some pictures of it here.

It’s a blast to fly, but it doesn’t exist in real life.  It deserves to though, so I’m going to try to build it.

Since the thing needs 4 motors, each on their own servo, plus normal flight surfaces (2 ailerons, 2 elevators, and a rudder) I need a total of 13 control channels; 14 if I want retractable landing gear. The only radio I know of that would handle that is a Futaba 14MZ, but they’re about $2100.

The other complication is that the thing needs at least two gyroscopes for hovering stability to compensate for motor differences, and possibly a third for yaw control. They have to be on-board, and mixed into the other inputs. Since the pitch / roll gyros each affect all four motors, the mixing required is more complex than a typical R/C craft.

Technically speaking, the thing takes the same inputs as a normal R/C plane, with one extra value for motor pod direction. That means I’d need to send it 5 signals (6, including landing gear) to control it. If I could program an on-board computer to read the signals, read the gyros, then produce all the outputs, I’d be in business.

That’s where microcontrollers come in. Also called PICs (Programmable IC’s), these little chips are like the CPU of a computer, but they have on board memory, input and output ports, and a bunch of other stuff that make them pretty much stand-alone. You program them from a computer, and when powered up, they run your code. They’re quite cheap (~$4) and come in a ton of flavors to suit various needs.

Three weeks ago, that was more than I knew about them. I knew they existed, but didn’t know much more. I started surfing, and talked to a couple friends who’ve worked with these things in the past, and eventually bought a starter kit from a company called MicroChip. The kit (PICKit 2 Debug Express) comes with a development environment (lets you author and test code), a programmer (puts the code from the PC onto the chip), and a ‘demo board’. The demo board has a mid-range chip on it, along with a bunch of lights, a button, a knob, and some extra space for mounting your own stuff.

The whole kit cost me about $80, and I’ve already got it moving servos and listening to my R/C transmitter (DivX AVI).

Now that I know more about it, I wish it was a little faster and did 16 bit math - 8 bits of precision is a little lower than I’d like, but I worry if I go higher, the extra time spent getting an 8-bit chip to do 16-bit math will leave me little time for the rest of my code. Time will tell - I’m going to stick with this one for now and see how far it takes me. Every time I read the manual I discover something else I didn’t know it could do, and the fact that it’s a very simple chip means it’s very quick to learn on.

More as it happens…

Halloween in Vegas - The Fun Police have arrived

Friday, November 3rd, 2006

My friend Kevin and I have been going to Vegas for Halloween for 4 years now, and up to this point, it’s been a blast.  Lately though, Vegas seems to be losing its edge.  Seriously, it’s now this weird amalgamation between ‘DisneyLand’ and ‘Sin City’ - People are wandering around the casinos with their kids.  As it becomes less adult, it’s also becoming more regulated.  We’ve been going through the hotels with full masks on for a few years now, in and out of clubs, and never had a problem.  Not so lucky this time.  Read all about it here: How Tangerine ruined Halloween