GeometricTree

LogoTurtle

A programmable floor turtle

With Brian Silverman and Erik Nauman, we adapted an Instructable Arduino floor turtle robot to run Brian's LogoTurtle.

These instructions will teach you how to construct and begin programming your own LogoTurtle robot.

"The idea of mucking about in programming is, for better or for worse, not very popular in grown up computer science. Programming these days has become more of an engineering discipline with the idea being that you should do things once and do it right. Logo is and always was about debugging. Before the do it right stage there are always dozens if not hundreds of do it not-quite-right stages. This iterate-iterate-iterate then iterate again is not very prevalent in work with microcontrollers. LightLogo and TurtleLogo try to make microcontroller programming interactive but they are far from the mainstream."

Brian Silverman

CalibrationSquares

Kits

Kits, both unassembled and assembled, are available.

3D Printing and Assembly

1 x Ball bearing caster
1 x Chassis
alternately, 1 x Laser Cut Chassis
2 x Wheels
2 x Stepper bracket
1 x Pen Holder / servo bracket
1 x Pen Collar

1 x 5/8" Caster bearing
2 x 1 7/8" ID x 1/8" O-ring
10 x M3 x 8mm pan head screw
4 x M3 x 6mm flat head screw
12 x M3 Nut

3D print the models at .3mm layer height, 2 shells, 25% infill, with the exception of the chassis, which should be 3D printed at 35% infill.

Insert the 5/8" ball bearing as soon as the 3D printer stops for an easy, perfect fit. The ball may not rotate when the turtle is moving but that is fine.

This variation of the robot uses a different microcontroller than the original version. Please follow steps 3 through 6 in the original instructions to assemble the 3D printed parts and attach the stepper motors.

Consider using a small piece of wood to shim between the 3D printed stepper motor mounts. This reduces the amount of bowing in the chassis and helps keep the wheel base measurement consistent across turtles. When you calibrate your turtle later, you can get the turtle to turn almost perfectly 90 degrees by finding the correct length of shim that the robot needs.

CompletedElectronics

Remove the 3D printed pen holder/servo bracket so you have access to the complete underside of the turtle before you build the electronics.

The turtle's electronics are built around the affordable Adafruit Metro Mini microcontroller.

Additionally, please purchase the following parts:

2 x Geared 5V Stepper
1 x ULN2803 Darlington Driver
1 x Half-size breadboard
1 x Male-male jumpers
1 x Micro servo
1 x SPDT slide switch
1 x Male pin header
2 x 2 x AA Holder
1 x USB micro cable
1 x Photo cell (CdS photoresistor)
2 x 10k resistors
4 x AA Batteries


BatteryHolders

Attach the battery holders according to the Instructable directions.

Once the battery holders are attached, route the wires through the slots on the underside of the turtle.

02

Using the rails on the top of the chassis as a guide, use a knife to score the backing on the breadboard without cutting the adhesive underneath. Remove the backing and attach the breadboard to the top side of the chassis. Orient the breadboard so the higher numbers are towards the right side. The breadboard will hang out over the rear of the turtle.

Building the Electronics

If you have never used a breadboard to assemble a circuit, please see this tutorial to familiarize yourself.

03

04

With your turtle oriented as shown in the image above, plug the black negative lead from the left battery holder into hole 3 on the rear negative rail. The red positive lead from that battery holder plugs into hole h26 on the breadboard.

The black negative lead from the right battery holder plugs into hole g26 on the breadboard. The red positive lead from that battery holder plugs into hole b30 on the breadboard.

05

Choose a color of jumper wire to use for the rest of the positive wiring on the breadboard. I chose orange.

Connect a jumper wire from the second hole on the far positive rail to the first hole on the positive rail closest to you.

06

Connect a short jumper wire from the second hole on the close positive rail to hole b1 on the breadboard.

07

Connect a short jumper wire from hole 13 on the close positive rail to hole a16 on the breadboard.

08

Connect a jumper wire from hole 27 on the far positive rail to hole b29 on the breadboard. (The photo shows hole 26 on the rail, but the jumper wire should be connected to hole 27 on the positive rail).

09

Connect a jumper wire from hole 25 on the far positive rail to hole d25 on the breadboard.

10

The final positive connection is from the far positive rail hole 28 to hole j28 on the breadboard.

You have now completed the positive wiring, excluding the power switch.

11

Now you will wire the negative leads on the breadboard.

Choose a different color jumper wire for your negative connections. I chose yellow.

Start with a small jumper wire between the far negative rail hole 14 to hole j16 on the breadboard.

12

Next, connect a short jumper wire from hole 29 on the far negative rail to hole j29 on the breadboard.

14

Connect a jumper from the far negative rail hole 26 to the near negative rail hole 26.

15

Connect a short jumper from hole 7 on the near negative rail to hole a6 on the breadboard.

17

Insert header pins into the breadboard from b16-20 and c21-25.


18

Insert three header pins in holes i27-29 on the breadboard.

18

Carefully insert the pins for the darlington driver, bridging the gap in the breadboard. The notch on the darlington driver should face the right of the breadboard. The pins go in holes e16-24 and holes f16-24.

19MetroMini

Before you solder the header pins, load LogoTurtle onto the Metro Mini.

If you are using a Mac, please follow the directions at Erik Nauman's blog to load the Blink sketch in the Metro Mini. You must replace the sketch the Metro Mini ships with or else your Mac may hard crash, requiring a force-restart.

Windows users should be able to proceed without any additional installations or modifications to the Metro Mini.

Download the latest version of LogoTurtle.

Connect the Metro Mini to the Mini USB cable. Connect the USB cable to your Mac or PC.

Open the Assembler.jar in the logovm folder.

Click the ASM button. The console will report back a number of words.

Click Download. The console will report how long it took and produce a string of hexadecimal numbers and letters.

Success should report written in 1 second with the hex string: 0000 - 940C 0034 940C 3F00 940C 3F00 940C 3F00.

Failure takes 8 seconds and the hex string will be something like: 0000 – FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF.

Quit the Assembler.

Open Logo.jar in the logo folder.

Click the Download button. After the console reports Downloaded, type the following in the console (the italics are what LogoTurtle should respond):

print 42
42
print 4 + 5
9

Quit Logo.jar.


Unplug the Metro Mini from the USB cable.

Solder the header pins to the Metro Mini.

20

Carefully insert the header pins from the Metro Mini, bridging the gap in the breadboard. The pins closest to the front of the breadboard start in hole c1 and continue to c14. The pins on the far end of the breadboard start in hole g1 and continue to g14.

21

Choose one color jumper wire for the left stepper motor wiring. I chose gray.

Connect a jumper wire from hole j9 on the breadboard to hole j17. This connects pin 5 on the Metro Mini to pin 8 on the darlington driver.

22

Connect a jumper wire from hole j10 on the breadboard to hole j18. This connects pin 4 on the Metro Mini to pin 7 on the darlington driver.


Connect a jumper wire from hole i11 on the breadboard to hole i19. This connects pin 3 on the Metro Mini to pin 6 on the darlington driver.



Connect a jumper wire from hole i12 on the breadboard to hole i20. This connects pin 2 on the Metro Mini to pin 5 on the darlington driver.

You have completed wiring the left stepper motor array.



Choose a different color jumper wire for the right stepper motor wiring. I chose green.

Connect a jumper wire from hole i8 on the breadboard to hole i21. This connects pin 6 on the Metro Mini to pin 4 on the darlington driver.


Connect a jumper wire from hole i7 on the breadboard to hole i22. This connects pin 7 on the Metro Mini to pin 3 on the darlington driver.


Connect a jumper wire from hole j6 on the breadboard to hole j23. This connects pin 8 on the Metro Mini to pin 2 on the darlington driver.



Connect a jumper wire from hole j5 on the breadboard to hole j24. This connects pin 9 on the Metro Mini to pin 1 on the darlington driver.

You have completed wiring the left stepper motor array.



Connect a jumper wire from hole h4 to hole j27. This connects pin 10 on the Metro Mini to the servo array.



Connect the wires from the left stepper motor to the left header pins on the breadboard. Make sure the red wire matches the jumper wire on hole a16. Connect the wires from the right stepper motor to the right header pins on the breadboard. Make sure the red wire on the stepper motor matches the jumper wire from the far positive rail to hole d25.



Insert the leads from a 10k resistor in holes b4 and b6 on the breadboard.

The power stays "on" for some time after you pull the USB plug. When the power to the Metro Mini gets restored it looks to the Arduino more like a reset than a power up. By adding a 10k resistor between the 5V pin of the Arduino and GND, residual power is drained from the Metro Mini.



Insert a 10k resistor from hole 8 on the near negative rail to hole b9 on the breadboard.



Insert one lead of the photo cell into hole 5 of the near positive rail. Insert the other lead into hole a9 on the breadboard.



Insert the SPDT power switch into holes a28-30 on the breadboard.

Reattach the 3D printed pen tube/servo bracket.

Using the Fritzing diagram below to double-check all your wiring.

FritzingDiagram

Congratulations! Your LogoTurtle is constructed!

Next you will calibrate the turtle to make sure it is working properly.

Place a pen in the 3D printed pen collar. Make sure the the pen is in contact with the paper below the turtle.

Switch the power switch on.

Press the reset button on the Metro Mini. The turtle will draw a square. It should have angles close to 90 degrees and the lines should meet.

If the square is skewed or not quite square, adjust the wheel base by moving the wheels in or out on the stepper motors. Set on a ruler, a well-calibrated turtle should have a wheel base of 112mm. Use a heat gun to warm the wheel hub if it is too snug to fit on the stepper motor.

CalibrationSquares

If the turtle appears not to be making full 90 degree turns, you might need to place a shim between the stepper motors. This turtle needed its steppers to be spread slightly to get the square nearly perfect.

Shim

Next, you will add the servo to the floor turtle so it is able to raise and lower the pen.

Servo01

Plug the servo into the three header pins on the breadboard. Be very careful about connecting the correct pins to the correct servo wires. The rightmost wire on the breadboard is negative, and the corresponding wire on the servo is brown colored.

Servo02

Plug the turtle into the USB cable, plug the USB cable into the computer, and open Logo.jar. The servo will move to the down position.

Servo03

Use the small screw that comes with the servo to attach the horn to the servo. Mind you do not turn the servo while you attach the horn.

Servo04

Snip the support in the middle of the bracket to remove it. Install the servo in the bracket with two screws. Make sure the wires come out of the right side of the servo when it is installed.

Servo05

Power on the turtle. The servo will move to the up position.

Open the test.txt file in the logo directory with a text editor.

text01

text02

Add pen commands to the square procedure. It is a good idea to ask the turtle to wait 1000 after putting down the pen to make sure the pen is on the paper before the turtle begins moving.

logo01

Connect the turtle to the USB cable. Click the download button in logo to transfer the updated square routine.

text03

Remix the square procedure and move the pen commands to the startup procedure. The startup procedure is run when the reset button is pressed on the Metro Mini.

remix

arcs

Experiment with the arclt and arcrt commands. The syntax is arclt angle radius. This turtle drew arclt 360 100.

photocell

You can take readings from the photocell sensor. The photocell is plugged into A0 on the Metro Mini, so print a0 or repeat 100 [print a0 wait 100] can be interesting starting points.

to startup
pd wait 1000
let [n a0]
repeat 200 [
arcrt 10 :n
make "n a0
]
pu
alloff
end

Troubleshooting

Double-check all your wiring against the circuit diagram above.

If LogoTurtle fails to load on the Metro Mini, load the example Blink sketch from Arduino to confirm your computer is communicating properly with the Metro Mini.

trouble01

Make sure that when the servo is in the down position that the pen holder rests flush on the robot's pen holder. If the pen holder on the pen is not in contact with the robot the lines will have weird backlash as the robot changes direction and the lines will not look beautifully crisp. The green lines in the example below were drawn without contact with the robot, the red with contact. Notice the line segments after the 45 turns.

Consider joining the LogoTurtle google group.



Thank you to Brian Silverman and Erik Nauman for helping this dream come true.

Thank you to Michael Tempel for an extra set of eyes on the documentation.

This work and images copyright 2016 Josh Burker