Sunday, March 1, 2015

Bit Char-G - Do you like my body?

The battery goes on top.  If I could get my hands on a "fat" 30ma cell, I could probally put it in the bed.  I wonder if I can get my hands on a Estes or Cheeson micro battery...

It looks good to me.

Friday, February 27, 2015

Bit Char-G - Doing research long after it matters. And making a 1/64 scale proportional car.

I want some r/c cars to drive around my computer room.  The room is about 10x10, and has a bunch of furniture and other stuff in it.  That means even 1/32 scale cars are a bit big, if I want to set up a course and do laps.

Several years ago, I was into these cars called Bit Char-G.  They were made by Tomy, and sometimes were sold on the MicroSizers name by Hobbico in the US.  I got most of mine from a little Japanese mall, and mail order.

Here's a Bit Char-G next to a AAA battery...

Their turning radius is about a foot, so they're great for rolling around on linoleum floors.

So lets talk about the cool stuff on these cars.  First, they have replaceable final drive gears.  They come in three color coded sets.

Now, this seems great, excepting they're not proportional.  They use a magnet and field coils to steer, and have what amounts to a pager motor to make them go.  Admittedly, they have enough power to really go, and be challenging to drive... so that's not the problem.

Now.. how do you give proportional steering to a car that's 55mm between body mounts.

Happily, there are servos that are "about the right size".  The one thing that's missing, is a decent micro speed controller.  "micro" speed controllers seem to start in the "few amp" range, and go up from there.  The smallest brushed one I can find, is a 3amp one for airplanes.

What we need here, is a 1 amp speed controller, with coast, brake, and reverse.

But.. do we really need 1 amp?  I pulled 1 amp out of the air, based on the run time of the car.  Which is "a few minutes" on 50ma.  I think we need to do some testing....

So testing we shall do.  From a fully charged 50ma NiCd cell...

No load: 33ma
Some load: 55ma (finger dragging on the wheels making them slow down)
Full stall: 99ma

I was expecting "amps" not under a tenth.  But.. I'll take that.

The usual answer for "I need a really tiny ESC" is to gut a larger r/c servo, glue the pot  on center, and call it a day.  I want a really good tiny ESC.  If this project pans out... I'll need to do some research to find that sort of thing.

I started digging through my gear to see what I have that might suit this build.  

How are we going to squeeze a battery, ESC, Servo, and RX into that?  Specifically this gear:

It looks like the receiver would fit upside down, without interfereing with most bodies.

And the servo looks like it will fit flat  if I carve out the bottom

But.. in the end, those weren't going to work tonight.  If i want a chassis like that, I'm going to need to build this up as a pan car.  (a completely sane, if time consuming option..)  That, was not in the cards tonight.

Speaking of tonight, I needed an ESC.. now.  Thankfully, a servo was willing to spill it's guts for me.

I'm decent at soldering, but lets say this was a challenge.  Much to my joy, it worked.

Thursday, February 19, 2015

A practical airframe. The QFO could fly.

Finding time to work on hobbies is.. a challenge.  Sometimes, you have a cat sleeping on your work surface.  Everyone, meet Al.  

Building inside a QFO frame is an interesting task.  In order to get all of the power wires going the right way, the speed controls all needed to face the same way.  And to have clearance for the battery, and flight controller, the speed controls needed to be tucked into the sides of the airframe.

To get the motor wires going the right way, I soldered them on backwards.

Trying to take a photograph of the inside of the QFO isn't easy.  Here's where I mounted the speed controls.  

I still dislike PDBs.  So I built another one of the Warpquad style wiring harnesses.

And here's the power harness in place.  Somehow, I didn't get a picture of the cable end I built, that includes a JST lead to power the lighting system.  I still plan on using the balance connector to power the video system on this quad.

With everything on board, excepting an antenna, and a camera, it comes to about 400 grams.  

It's all a really very tight fit.  I need to dig up a receiver with CPPM so I can get rid of most of that wiring harness.  Somewhere, I have a couple of those.  

Someday soon, it will fly.  

Next up, is figuring out the camera situation.  I plan on putting an 808 based camera under the airframe.  And.. so long as I don't try to do any high performance flight, I could use the video feed off of the 808.  I'm also considering cutting a hole in the side of the fuselage to stick a tiny camera through.

I should also finish the lighting rig.

Friday, February 6, 2015

Building a QFO - That motor situation.

The QFO is a fiberglass shell, 250 class, quadcopter frame.  The bare shell is about 65 grams. HobbyKing claims 47 grams.. but I think that's without any landing gear, or magnets installed.  "My QFO, ready to install motors" was 65 grams.

Speaking of motors, that's the subject of today's blog post.  They say the frame is designed for 1506-2208 motors.  If you look closely, you'll see that my motor is an 1806.  It will not fit in that hole. 

I mean, that "really" does not fit.  My Turnigy 1704's will fit, but these DYS 1806's are a no go.

The material that makes the frame is very nearly paper thin.  It's thinner than cereal box cardboard.  So running a dremel around in the hole very quickly takes care of the hole size. 

If you're sharp eyed, you'll see that's not actually a dremel.  It's a $9 "multitool" from Harbor Freight.  It's DC, quiet, and I expect it to last all of say.. one project. 

What I really like about this airframe, is that the motors end up recessed.   I think it's a really neat look.  I'm also wondering how you'd get a 22mm motor on there.  As you put in bigger motors, you're going to have less and less fiberglass to mount to.  I think putting 22mm motors on there would probally just lead to them ripping off in the first crash.  I wouldn't try mounting anything bigger than a 18mm motor internally.

I found that mounting the motors to the bottoms of the arms is a valid mounting solution, and while they don't end up recessed, you get around the prop clearance issue, and you retain all of the strength of the arm.  And with the additional prop to frame clearance
The QFO doesn't have a whole lot of internal space.  Stuffing this airframe is going to be a challenge, especially since I plan on getting some reasonable endurance out of this, and hanging an 808 based camera underneath it.  

Here I have all the motors installed, a 1500mah 3s battery, a 200mw 5.8ghz transmitter, a LED power supply, an OrangeRX reciever, an ESC, and the Flip32+, are all in the frame. 

The only way to get the 1500mah 3s battery in there is across the X.  It will fit longitudinally, or transversely if you rotate it after you install it, but having to rotate it after it's put in the airframe means I can't use the corners to hold the VTX or reciever, or LED power supply.  This does make me wonder how it will fly, as the big battery is going to make the polar moment very different across one axis than the other.  It will induce a diagonal pitch movement every time it tries to tip to go forward, or slide left and right. 

We'll need to see how that works out. 

Getting good flight time from an airframe has a lot of factors.   You need raw watt hours to power the motors.  You need lift to get those watt hours into the air.  You need to not waste energy.  Not wasting energy, really means having an aerodynamic frame, and efficient props.  The QFO is "designed" for 5x3 props, which aren't exactly stellar when it comes to turning motor watts to thrust.  So I decided to try a 6x3. 
It fits!  But only just barely.  That really is just 3mm of clearance under that blade tip.  But "any" clearance is enough to make this work.  Hopefully it won't induce to much airframe noise.  I plan on mounting the FPV camera through a hole in the side of the frame, without any vibration damping, so I may be forced back to 5x3 props in the end.  
5x3x3's always have looked good to me.  So I threw that on a motor to see how it looked.  Sadly the extra x3, while it does produce more lift, you also get 50% more tip losses.  I think 5x3x3's will lead to reduced flight time versus 6x3s.
 So that's it for the first night of building.   I still need to relieve each motor hole just a little.  And then I can get to figuring out how the ESCs will mount.  I think they're going to get foam double stickied tape to the inside top of the airframe.

Monday, January 12, 2015

The KK 5.5 board. Five point five you say? Yes...

Flying quadcopters is a tricky business. They take a lot of math, and fast acting controllers to keep them airborne. One of the early common boards, is the KK board.

Trying to cheap out while buying my second flight controller, I was looking at the alternate boards on HobbyKing.  They had this blue flight controller...

Which I have since learned was, or is, a clone of the original KK board.  It's also known as the "black" board. 

This board, in particular, has a ATMega 328 on board.  And as opposed to what you'll find in a multiwii based setup, three separate gyroscopes.  Sadly, there are no accelerometers, so the board has no way of figuring out which direction is down.

The board doesn't support CPPM.  It doesn't know what horizon mode it.  The board's forward direction can not be changed.  It can't be programmed without an ICSP programmer.  However, it does allow for some onboard tuning.

There's no button on the board, so "on boot options" are commanded via the transmitter, and the three pots on the board.  By swinging a pot to the full left position, you command the board to enter gyro reversing mode.

The board does have a built in arming function,  With the throttle at low, you swing the rudder full right, or left, to disarm, or arm.  When armed a red light shows on the board.

So what does the board do?  You might ask.  Well it supports about a dozen mulitcopter configurations, with one to eight motors, some stacked, some not, and some stabilized by servos.  It's really quite the resume.  But no mater what you fly, it will be in acro mode, all the time.  Because the KK doesn't know what way is down. 

The default configuration is the "plus" configuration.  With one prop leading, as opposed to the usual x configuration most of us are accustomed to flying.  The only way to change that setting, is by flashing new firmware on the board.

These boards retail for $12-16.  I can't imagine a situation where this board would be preferable to a Flip, or Naze.  If you have an unending, burning desire to fly one of these, be sure to pick up a package that also gets you a ICSP programmer.  You should also be buying a set of at four servo extensions so you can wire up the receiver to the FCS.

I think the nicest thing about this board, is that the channels are well labeled.  Unlike the Flip, KK2, or Naze32.

Sadly, the only lesson to be taken from this, is that quadcopter FCS technology has really advanced.   The KK 5.5 is a relic.  A cheap relic, but for $4 more, you can get a Flip based board, so the decision isn't a difficult one. 

Monday, December 29, 2014

Quadcopters - Learning the FPV thing.

Friday was a bit of an adventure. I had a visit with the powers that be, and after getting the all clear from the local judge, I was free to go out and play. As it turns out, so was SwitchElectrician.

SwitchElectrician came over, and we did some flying. He brought his X-Factor and his Diatone #29 / Flip 230.

We got some onboard video of his flights.  There's some good views above Northlake.  Keep in mind, it was really windy during these flights. 

I also got in a few FPV flights.  But only one with onboard video.
It got off the ground, one motor shut off, and it crashed.  No damage beyond having the 720p camera fly off.

He also  did some beauty shots of the quadcopters.  ...  We did do this wrong though.  The photo session was done AFTER we flew that afternoon. 

Since it's my blog, we'll start with my quad.  Here's my X-Factor: 
And the backside. 
 And here are the group photos. 

They're a pretty good looking group of quadcopters. 

Flying FPV is a strange experience.  I can fly a flight simulator without any problem. But the sound matches what I'm seeing.  When flying FPV, the sound of the quadcopter feels louder.  These 250 quads are powerful, and loud.  And can hurt.  Being under the hood makes that whole equation seem a lot more scary. 

Also, SwitchElectrician and I were flying at a big field.  With almost no frame of reference.  It felt very lonely and scary flying in that field. 

When I went to fly on Sunday, I chose to fly in my back yard.  I broke a few more props, but I had a much better time, as I had a frame of reference to work with.

Until next time....

Monday, December 15, 2014

There Are Four Quads.

Deadbug: A method for wiring of electronic circuits that involves attaching the components to a substrate, upside down, and then connecting the contact points, point to point.  

Saturday, I went over to SwitchElectricians place, and we spent the day messing with quadcopters.  It was a productive day, we had three different quads get completed.  

Acro quads are a strange.. They're usually an attempt at the minimum airframe to fly, but often err on the "less than minimum" amount of airframe.  That means you need to get really creative with mounting things to it, beyond the usual "hey this isn't the right size" issues that are par for the course. 

In deadbug style, here's the wiring that I did on the HobbyKing Maltese frame.  Now I'm a little disappointed I have the Velcro on there, it doesn't show my cross wiring job.

This quadcopter is flying on a set of 1704, 1900kv motors.  Spinning 5x3 props.  The battery is a 800mah 2s pack.  The flight controller is a KK clone from HobbyKing.  I'll talk about the board later, but for now, lets say I don't like it very much.  It's flying weight is very, very light.  350 grams IIRC.  

Mounting the motors was somewhat difficult.  The motors have a two available mount patterns.  The ones drilled into the motor, and then a X shape bracket you can put on it to mount to larger motor mounts.  The bracket is so large that it is bigger than the arms on the quad.   The built in bolt spacing is between two of the three bolt patterns on the arms of this quad.  To make it work, I had to drill out the smallest spacing with a slightly larger drill bit.  the washers make up for the larger motor mount holes. 

M2 screws and washers are a pain to work with.... 

The board has a fixed "forward."  So the front of this thing, unless I get some kind of adapter board, will make this a "plus" configuration quad.  When I was test flying it, this shape really messed with my head.  You'll notice the red tape and red prop, I did that before I flew it because I knew my brain wasn't going to handle the plus set up very well.    That said, it did fly, and was stable as could be expected from a board without accelerometers. 

Oh look, more deadbug.   The receiver has moved, and there's a few extra wires hanging off the chassis.  Also, the motor leads have lost 5" of excess wire.  In this picture, the quadcopter has a 3s 1500mah battery in it.  It will fit a 3s 2200 as well.  I haven't tried to see if it will balance with a 1000mah 3s in it yet. 

Speaking of balance, the female balance plug on the right side of the picture, is how we decided we were going to provide power for the FPV gear.  It means we can turn on and off the video gear, without the problems that come from switches.  And it gets the video ground as far away from the motor grounds as we can manage.  It should be "better" but I haven't thrown a oscilloscope on the quadcopter to quantify those numbers.  At minimum, it makes me feel better.

The Naze32 flight controller moved twice since the last photo.  Because the receiver came off the top deck, the cable for the Naze32 ended up being to short. 

Standoffs are a wonderful thing.  To clear the speed control wires, I had to raise the naze32 over the motor deck. Eventually I'll be using the same stack of standoffs to carry my HD flight camera, but that's for another time.  

I'm still trying to decide how I am going to dress the power and signal wires for my FPV gear.  You can see the trimmed plug for the balance connector that provides power to the FPV rig. 

The starboard elevation. I'm a little worried about the receiver location, but it's in a case, and should be able to take any hits. 

 The video transmitter doesn't stick past the chassis, so should be safe.  The front end of the X-Factor is a very, very busy place. 

Doing hobby work at your computer desk isn't recommended.. but it's what I do.   I like how it turned out.  In the next week or so, the flight HD camera mount will be fabbed up, and I'll get my hands on some circular polarized antennas.  (or make them...)

SwitchElectrician also had a project to work on.  He picked up the ultra light 250 racer frame from HK.   We built that up too.  It's flying on some 2204's, 20amp Afro speed controls, a 1.5ah 3s battery, and 5x4.5 props. 

Let me tell you, it wants to move some air.  We need to get it on a scale, but I think it may have a 4:1 power to weight ratio. You can peek in at the winding on the motors, and they're positively beautiful.  I suspect they were hand wound with how the wire is stacked on each pole. 

Saturday was a productive day.