TurTle-T

TurTle-T is a robot inspired by a turtle and reminiscent of the LOGO language developed in the 1960s by Seymour Papert at MIT (Massachusetts Institute of Technology). The LOGO language has always been widely used to teach programming to children and adults. TurTle-T was created so that it could be very easy to assemble, without the need for any tools, and also easy to program, in principle with a block language. It can perform various activities, such as moving forwards and backwards, making curves, going over small obstacles, detecting and dodging objects, following lines and producing sounds, reaching a complete melody.

Electronic Parts

• 2 DC (3-6V) motors with gearbox
• 1 mini switch KCD11-101 (10,4mmx15mm)
• 1 H-bridge module (HG7881-L9110S)
• 1 Arduino NANO (with USB cable)
• 1 IR sensor module (TCRT5000)
• 1 ultrasound sensor module (HC-SR04)
• 1 buzzer passive module (5V)
• 1 battery holder (4x AAA)
• 1 mini protoboard (170 dots)
• 22 M-F jumpers (some extras may be needed - here we use 10 cm long jumpers, however, those of 15 or 20 cm are easier to work with)

3D Printed Parts

• Parts printed by additive manufacturing, available at https://www.thingiverse.com/thing:6143471

Tools*

• soldering iron
• small screwdriver
• hot glue
• cutting pliers
• solder tin
• insulating tape or heat shrink tube
• sand

*adult supervision is required

• Take four M/F jumpers (2 brown and 2 orange)
• Remove the plastic protection on the female end

• Cut the metallic connector
• Strip the jumper tip

• With pliers, cut the small plastic end that has a hole in the motors, sand if necessary, to be very flat
• Solder each pair (same color) to the motor terminals (here you can use a piece heat shrink tube)
• A little hot glue should help secure the jumpers

• Take two M/F jumpers (red)
• Remove the plastic protection from one jumper at the F end and the other at the M end

• Cut the metallic connector
• Strip the jumper tip

• Solder these leads to the two switch terminals (so we must have jumper M and jumper F soldered to the switch)
• Here you can use a piece heat shrink tube

• Take two jumper M tips
• Strip the jumper tip
• Solder these leads to the battery case wires
• Use heat shrink or electrical tape to insulate
• The positive M jumper will be connected to the F jumper of the switch
• The negative M jumper will be connected directly to the protoboard

The TurTle-T has two direct current motors, positioned in an inverted way, which move two pairs of wheels each (an active one coupled to the motor shaft and a passive one coupled to the fixed axle of the chassis) by means of a pair of tracks. Thus, motor A has front-wheel drive on the left side and motor B has rear-wheel drive on the right side.

Since the motors are reversed, in order for them to move the TurTle-T forward or backward, they need to have reversed directions as well, so that the motion rotates the tracks in the same direction. To make curves, there are two ways.

The first is to rotate the robot on its center, so that the two tracks rotate at the same speed and at the same time, in opposite directions. By controlling the direction of rotation of the motors, it is possible to make the TurTle-T rotate clockwise (turn to the right) or counterclockwise (turn to the left). This will be the default way the TurTle-T will make changes to its trajectory.

Figures on the assembly show rubber treadmills, which can be found at www.tkxhi.com. However, they are available in https://www.thingiverse.com/thing:6143471, treadmills that can be printed once using the corresponding STL file.

• fit the first motor into the chassis so that the flat part of the housing faces the inside of the chassis
• the motor lugs must fit properly into the holes on the side of the chassis
• motor jumpers must face up

• fit the second motor, tilting it a little to fit the shaft on the opposite side
• remember that the motors need to be in opposite directions
• motor jumpers must face up

• fit the fastener of the motors so that they are securely fastened
• you may need to rotate the fastener a little to get it to fit snugly

• insert the switch, starting with the jumpers, from the bottom of the chassis
• slightly press the switch against the chassis so that it snaps into place
• adjust the jumpers, so that each one of them passes through one side of the fastener of the motors

• fit the master wheel onto the motor shaft
• fit the slave wheel to the chassis

• fit the master wheel onto the motor shaft
• fit the slave wheel to the chassis

• fit the treadmills

• Here the figures display silicone treadmills that can be found in the TkxHi store (www.tkxhi.com)
• They are easier to adjust, as they are very flexible, in addition to producing greater adherence to the floor.
• However, it is available in https://www.thingiverse.com/thing:6143471 the treadmill STL file (3D printable)

• considering that the Arduino Nano is already properly attached to the protoboard (see step 1), fit this set into the base shell
• also fit the H bridge (note the position of the terminals for connecting the motor jumpers)

• Carefully position the IR module inside the case, so that it is well supported and the sensor (blue and black that look like 'LEDs') are fitted in the bottom hole of the case
• fit the holder of the case, forcing it slightly so that it opens and embraces the case
• note that there is a groove on the side of the case that must fit with the holder (this will get stuck in the ultrasound set)

• fit the ultrasonic sensor inside the case, so that the terminals are facing upwards
• fit this set in the holder, so that the case is "embraced" by the holder

• note that the ultrasound holder has a cutout that must face downwards

• fit the battery case on the support as shown in the image and so that the jumpers are facing upwards

• note that the battery holder also has a cutout, which, like the ultrasound, must face downwards

• fit the buzzer into the shell so that it faces the inside of the shell (it will point towards the arduino)
• insert carefully until you hear a click
• be careful with the shell, it is fragile

• identify the front of the chassis
• fit the ultrasound set
• the top of the ultrasound holder must face the top of the chassis
• nothing should be forced

• the set should look like this

• the battery pack must be fitted to the rear of the chassis
• fit the battery pack
• the top of the battery holder must face the top of the chassis
• nothing should be forced

• the set should look like this

• fit the set with the Arduino and H-Bridge on the top of the chassis
• support one of the sides first and diagonally force slightly until you hear a click, fitting the other side
• the image suggests the place where it can be easier to pass the jumpers
• be careful not to trap any of the jumpers that come from the motors, batteries, switches, etc...

• after the set is well fitted and firm, you can use a small screwdriver to fasten the jumpers that come from the motors, on the H-bridge
• place wires of the same color on each pair of terminals
• the set should look like this

• adjust the IR sensor wires and fit the set in the ultrasound case

• fit the IR sensor wires passing through the opening of the ultrasound holder

• finally, fit the buzzer wires to the protoboard and fit the shell carefully
• remember that in each step, the wires must be inserted in the protoboard, according to the electrical instructions that follow
• check all assembly steps
• the TurTle-T must be as shown in the image

• the mini breadboard has 17 lines, numbered from 1 to 17, and 10 columns named from A to J. This system allows the indication of a specific point among the 170 existing in the breadboard
• the 5 points on the left (A,B,C,D,E) are connected on the same line, and the 5 points on the right (F,G,H,I,J) are also connected on the same line, however, E is not has connection with F, so the left side is separated from the right side by a cavity called “ravine” isolating them internally
• point F-3 highlighted in the breadboard image is on the 3rd line and column F, which is exactly the point where the VIN pin of the NANO must be connected, which is the positive input that comes from the batteries, in particular, after passing through switch that turns on/off the TurTle-T
• following the connection of the NANO to the mini breadboard, the other 3 reference pins are D13 (F-17), TX1 (B-3) and D12 (A-17). These are exactly the pins on the four ends of the NANO

• the TurTle-T has two direct current motors, where polarity does not matter, as the H-bridge is in charge of controlling the current flow in the motor, determining its direction of rotation
• the care you must take is to connect Motor B, which is the rear-wheel drive motor, to the correct terminals on bridge H
• the order of the wires (brown pair) does not matter. When testing the movement, if it is in opposite rotation, just invert these wires
• Similarly, motor A, front-wheel drive, is connected to the terminals indicated on jumper H, regardless of the order of the wires (orange pair)
• a simple movement test will indicate if it is necessary to invert the order of these wires to adjust the direction of rotation

• now let's finish connecting the motor control system, the H bridge. In addition to the terminals for connecting the motor wires, it has 6 M-type pins that must be connected to specific ports on the NANO
• as the wires will be connected to the mini protoboard, the jumpers used are of the M-F type, in this case, the wider range of jumpers, with the colors brown, red, orange, yellow, green and blue. These colors are very important, as they help to identify each jumper and where it should be connected
• the yellow and orange jumpers are responsible for powering the H bridge, and consequently the motors. So pay close attention because yellow is VCC/VIN (positive) and orange is Gnd/GND (negative)

• the ultrasonic module used is the HC-SR04
• it has only 4 connection terminals, 2 for power: Vcc (positive) and GND (negative); and 2 for emission and reception of pulses: Trig and Echo
• the jumper range for this module is violet, gray, white and black
• the highlight is the violet Vcc/5V (positive) and black Gnd/GND (negative) power jumpers

• The IR module that TurTle-T uses is known as TCRT5000, which has 4 connection terminals, 2 for power supply: VCC (positive) and GND (negative) and 2 more for reading signals: A0 (analog) and D0 ( digital)
• In fact, the module has, in addition to the TCRT5000 Reflective Optical Sensor, a potentiometer for adjusting the sensitivity of the signal reading, an LM393 comparator IC, in addition to other components, LEDs, resistors and capacitors
• the jumper range for this module is yellow, green, blue and violet
• the highlight is the yellow VCC/5V (positive) and green Gnd/GND (negative) power jumpers

• the TurTle-T produces sounds through the 5V buzzer module, which has 3 pins, 2 for VCC (positive) and GND (negative) power and the I/O to receive the signal sent by the Arduino
• the jumper strip for this module is grey, white and black
• the highlight is the violet Vcc/5V (positive) and black Gnd/GND (negative) power jumpers

• the black wire from the battery holder must be connected directly to the mini breadboard, at point H-4
• the red wire from the battery holder (type M) must be connected to the red jumper type F that comes from the switch
• 
  

• the other red jumper on the switch (M type) is what should be connected to the mini breadboard G-3 point
• this type of connection makes it possible to cut off the supply of current to the NANO, because before connecting to the breadboard, the circuit passes through the switch
• now TurTle-T is ready to be programmed
• just connect the USB cable to the NANO and the computer and start doing the first tests
• once programmed, just unplug the USB cable and turn on the switch and it will perform exactly what you programmed
• another care you must take when testing the programming is that he has the treadmills up, that is, not in contact with the table, to prevent him from starting to run and falling off the table
• OBS.: Remember to keep the switch off when you have it connected via USB, to avoid problems