County Fair

Why stop at the Maker Faire? Sabrina offered to organize an entry of the planes into the Yolo County Fair just for fun. Leo is a regular exhibitor who showed his very first Young Makers project there a couple of years ago.

When the kids dropped off their planes, the Junior Exhibits were just getting set up:

It might have been the first time all the completed planes had been in the same room together. Naturally, a commemorative snapshot was taken.

Back in the parking lot, Leo gave everyone samples of his baking entries, including these starfish s'more cookies, baked completely from scratch:

delicious!

And a couple days later, Sabrina texted us with the news that the planes had done very well indeed.

A Last-Minute Adjustment To The Towel's Motor Mount

Although the test flights were successful, the planes all still had problems with the motor mount flexing. The spinning motor put force on the vertical part of the bracket, shown below with arrow, bending it inward and making the plane hard to control. We brainstormed ideas on how to reinforce the bracket at the park, and decided to meet one last time before Leo took the plane to the Maker Faire.

 Doug had designed and printed a two-part reinforcement on his printer. The flat piece on the left goes underneath the foam board, while the piece on the right sits on top, behind the aluminum angle stock to keep it from bending backwards.

 With the above parts, 1/16" plywood, and two-part epoxy, the motors were remounted.

And voilà! The motor spins with no flex on the bracket now:

The Towel RC Plane Test Flights

The other evening we took the charged planes out to a local park and gave them their first test flights.

What were formerly foam presentation board, campaign lawn signs, bulk-ordered electronics and some zip ties were now planes. And they flew! The flights were a little dicey due to operator inexperience, but everyone got at least one relatively long run in. Here's one captured by Laurie:

And here is a compilation of all the planes tested that evening (John and Matt were not able to make it):

What a great end to the year—and what a fun year it's been. Here is Laurie's photo album with pictures from our meetings:

Young Makers Yolo 2012-2013

Leo will be showing his plane at the Maker Faire this weekend. Please feel free to stop by and see him at the Young Makers Booth on Saturday evening.

Planes Finished!

"The reality is you just can't build stuff perfectly the first time."~Jim

A little more last-minute tweaking: a bead of glue to keep the stabilizers upright, some modifications to keep the motor mounts from flexing.

Then a check on each plane's systems in turn...

...and the planes are ready to test. The kids would have flown them tonight, but for a strong north wind all day.

We're planning to meet again in a week and are keeping fingers crossed for better weather.

April Meeting, part 2: Adding Control Rods

April Meeting, part 1: Fabricating Parts with a 3D Printer

In an effort to finish the Towel RC planes by the end of spring, we've stepped up our meeting schedules to twice a month on weekend afternoons, rather than once a month in the evenings. The extra light and time has seemed to help, and the planes are coming along nicely.

The fun surprise of the last meeting was Doug's brand new Maker Bot 3D printer, which he had set up to print improved control horns for the wing elevons.

The printer is fed from the rear with two different colors of coiled abs plastic. It lays down the printing much like a 2D laser printer does, moving back and forth until the piece is formed.

Here are the two different-sized connectors, printed out on a grid which snaps off and can be easily filed down.

The next step is attaching the control horns to the wings, then programming them to fly correctly. Jim, a licensed pilot, talked each young maker through the process:

Next meeting the kids will be connecting up the servos, programming the radios, and moving closer towards flying the planes.

Wiring and Testing the Yolo Youngmakers Towel R/C Plane

As noted in the previous post, the next stage of the Towel build is configuring all the electronic components. Jim, our community mentor, offered to write up this more complicated part of the build.

by Jim Stewart, KC Micro Community Mentor

First of all, here’s a list of the parts we are using for our build. These instructions work for these parts. The instructions may not work for other parts.

• Transmitter - HobbyKing HK-T6A V2
• Receiver - HobbyKing HK-TR6A V2
• Servos - Hextronik HXT900
• Battery - Rhino 1750
• Motor - Towerpro 2408-21T-3A
• Electronic Speed Control - Hawking 20A or equivalent, 20 amp, 2 or 3 cell LiPo battery
• Battery Charger - IMAX B6AC+ Dual Power

Charging the Battery

The first step is configure the charger for the battery. Power up the charger and press the red button until the display indicates LiPo and then press enter.

Place the battery on a non-flammable surface. I like the small marble tiles available at Home Depot. Connect the battery to the charger using the big red and black leads for the power and the small 3-wire connector for the battery charging socket. Press start, confirm 3.9A charging current, press start again, confirm 7.4 volts. Press and hold start until charger beeps quickly. Press again to confirm. Battery should start charging.

Configuring the Receiver

Before we can configure the transmitter, we have to power up the receiver and servos. When the airplane is completed, the receiver and servos will be powered by the LiPo battery pack. For now, it’s much safer to power them up with 4 AA batteries in a Radio Shack battery box. These pictures show the wiring. You’ll have to find the connectors for yourself. I cut up an old CD-ROM audio cable to make mine.

From now on, any time I talk about where something is on the airplane, I will be looking at it from the back. In this case, the left servo is plugged into channel 1, the right servo into channel 2 and the battery pack into channel 3. The battery pack and the servos have to be plugged in exactly as shown. If you plug the connectors in backwards or some other way and you might destroy your receiver.

Next make sure the Bind jumper connector is installed in the BAT connector of the receiver.

Now we will power up the transmitter and receiver, bind them together and do some initial tests. Make sure there are eight fresh AA batteries in the transmitter and four fresh AA batteries in the Radio Shack battery box. Turn on the battery box, press and hold the Bind Range Test button on the transmitter, and then turn on the transmitter power. Hold the Bind Range test button for 10 seconds, then power down the transmitter and receiver. Remove the bind jumper and power up the transmitter and receiver. If the bind worked, you can now move the right and left servos by moving the right joystick right, left, up and down. Power down the receiver and move the right servo connector to the CH3 connector. Power up the receiver. You should be able to make the right servo move by moving the left joystick up and down. Power the receiver down and put the right servo connector back in CH2.

If everything tests out OK, we can now test the airplane with the flight battery and electronic speed control. Unplug the Radio Shack battery pack. Plug the Electronic Throttle Control (ETC) small cable into the receiver CH3. Be sure the wire colors line up like the picture below:

There should be no propeller on the airplane at this time. Check the transmitter and be sure the left joystick in in the full down position. Connect the LiPo battery. The ETC should beep loudly once. If it does, move the right joystick around and verify that the right and left servos move. Move the left joystick up slowly. The motor should start and run, with the speed controllable by the joystick. Slowly reduce the speed until the motor stops. Verify that the motor is running counter-clockwise as viewed from the rear of the airplane. If it is running clockwise you must reverse its direction. To do this, power everything down and disconnect any two of the three motor wires going to the ETX and interchange them. Verify that the motor is now turning counter-clockwise.

Configuring the Transmitter

The transmitter is presently configured to control a “normal” airplane, one with an elevator to control the pitch and ailerons to control turning. The Towel uses a different system, with two control surfaces serving as both elevator and ailerons. These surfaces are known as “elevons”. In order for the joystick to properly control the airplane, we have to configure the transmitter to “mix” the pitch and aileron signals from the right joystick and transmit the mixed signal to the airplane to control the elevons.

To configure the transmitter, we have to connect it to a computer and run a configuration program. I used the program Digital Radio available at http://www.sgr.info/usbradio/

Before we can run the Digital Radio program, we need a cable to connect the transmitter to the computer. There are several cables available, but I didn’t have one so I made my own. The cable I made connected the “Trainer” connector on the back of the transmitter with a serial port on my PC. The Trainer connector uses serial data, but is not RS-232 compatible. I made an adapter that converts the signals on the Trainer connector to RS-232 and then connected the RS-232 signals to a COMM port on my computer. Here’s a pinout of the Trainer connector:

To make my cable, I used an old Apple mouse cable, a SchmartBoard RS-232 module, and a extension serial cable. I cut the mouse cable and stripped the end of it, connected the shield to GND on the ShmartBoard, connected +5V Out to +5V, TTL Serial Data In to TD, and Serial Data Out to RD. Then I connected the ShmartBoard DB-9 connector to the serial port on my computer.

Download digitalradio.zip and extract digitalradio.exe. Run it and you should get a display like this:

Click the Mix Data tab halfway down the menu. Set the Mix 1 and Mix 2 options as shown below:

Click the Main Data tab halfway down and set all the Normal/Reverse Channels to R. Set Switch A and B to Null.

Click Radio > Send Settings. Click Radio > Get Settings. The parameters you set should show in the Main Data and Mix Data menus.

Testing Transmitter Mix Settings

Power up the airplane. Move the right stick up. Facing each servo, the right servo should move counter-clockwise and the left servo clockwise. Move the right stick down. The right servo should move clockwise and the left servo counter-clockwise.

Move the right stick to the right. Both servos should move clockwise. Move the right stick to the left. Both servos should move counter-clockwise. This concludes wiring and testing your airplane.

March Meeting

The Towel project continues. At the March meeting the focus was on attaching the deck to the wing.

First a template was placed to ensure proper alignment:

Holes and slots were cut for stabilizer and deck placement:

The deck was attached using good old zip ties:

Which invariably means that someone will try to see how they work on a finger:

But what's the point in making something if there isn't a bit of fun along the way?

Next up is bringing all the systems together: charging the batteries, wiring the servos to the receivers, and configuring the transmitters. After that we should be pretty close to having working planes.

February Meeting

"It's almost a rule as a maker: you will bleed occasionally." 

~Doug, group mentor 

The delayed parts have finally arrived, so at the last meeting Young Makers connected the batteries and cut out stabilizers for the wing. This involved more soldering, more cutting, and a little bit of heat-shrinking.

As you might imagine from the comment above, there was one sliced digit. On the other hand, no one got burned, which is a certain improvement.

soldering under mentor Jim's watchful eye

cutting stabilizers from foam mounting board

$2 hobby knife kits Doug found at Harbor Freight

no heat gun, but an acceptable substitute was found

We're aiming for another Saturday build day, since we can get more done in daylight and with the longer weekend hours. Before then, everyone will try to cut their elevons so they will move as Doug demonstrates, below:

Extra Build Day

In the middle of the holidays, we had the special opportunity to meet and build during the day, with daylight and extra time. Holes were drilled into pieces of a shower door for the motor mount. Servos and motor were attached and wired.

Next we have to add more electronics including battery, build the airframe with control surfaces and hook them up to the servos.

November & December meetings

Catching up—we've all been busy, but the meetings continue, and The Towel builds are slowly progressing.

The props, servos, and controllers arrived. Motor mounts were cut at the November meeting.

photo by Sabrina Granados

photo by Laurie Becker

photo by Laurie Becker

Last night was our December meeting. We had a guest, a teacher who has started a Young Makers group at her charter high school in Sacramento. We also had two new Young Makers joining us for the first time. Doug explained mounting the servos, which will be done at home to save time.

And we scheduled a special afternoon meeting for year's end. Maybe the combination of daylight and a break from school will get the planes to near completion.