Vorpal The Hexapod Assembly Instructions

BILL OF MATERIALS (BOM) FOR VORPAL H12 HEXAPOD

ROBOT BOM

• Electronics:
  • Beeper and 3 wire Beeper cable
  • Arduino Nano (marked R to indicate it is pre-loaded with robot software)
  • Potentiometer with 3 wires pre-soldered
  • 1 x HC06 BlueTooth Module with 4 x F-F jumper wires for making connections (Note: the HC05 has six pins but only four are used in this project)*** 1 x Servo Controller module with F-F jumper wires for making connections, plus 1 two-pin shunt
  • 12 x MG90 micro servo motors and associated servo horns
• 3D Printed Parts:
  • 1 x Chassis
  • 1 x Top
  • 6 x Legs
  • 1 x Switch bracket
  • 6 x Servo braces
  • 1 x Electronics Caddy
  • 1 x Stand
  • 1 x Eye/glasses Decoration
  • 1 x Joust accessory
• Miscellaneous:
  • 4 x 10mm diameter ceramic magnet, north pole marked. 3 are for robot top, 1 for eye/glasses decoration
  • 12 x socket head cap screw, 2.5mm diameter by 8mm long
  • 2 x #6-32 x 1/2" screw to fasten on/off switch bracket
  • 1 x L shaped hex driver for both kinds of screw

GAMEPAD BOM

• Electronics:
  • 1 x Battery/Switch Wiring Unit. (Note: the gamepad requires no BEC so you can use this fact to distinguish from the robot wiring unit)
  • 1 x four by four button matrix with associated connecting wires
  • 1 x Dpad Button module with associated connecting wires
  • 1 x HC05 Bluetooth module and four wires to connect it
  • 1 x Ardunio Nano (marked "C" to indicate it is pre-loaded with Controller software)
• 3D Printed Plastic Parts:
  • 1 x Gamepad base plastic part
  • 1 x Gamepad top plastic part
  • 1 x Gamepad button matrix cover
  • 1 x Switch Adapter
• Fasteners:
  • 4 x #6-32 x 1/4" screw for button matrix cover
  • 4 x #6-32 x 1/2" screw for Dpad button module
  • 4 x #6-32 x 1" screw to hold cover on gamepad

3D Printing the Plastic Parts

To obtain the STL files, please see Thingaverse.com and search for "Vorpal H12".

If you are 3D printing the plastic parts (as opposed to buying them pre-printed), here are some tips.

• RECOMMENDED PLASTIC is PETG. This plastic is easy to print, comes in both solid and translucent colors, and has no odor while printing so it is classroom friendly. The main advantage is that it is "springy" and has some give to it, and tends not to break or shatter. The H12 project has several parts that need this springy consistency to work properly. It is possible to use ABS as well. PLA tends to be too brittle.
• We print using 0.38 layer thickness. You can print with thinner layers but it will take longer.
• There are versions of several of the parts with and without brims. The brims help parts stick to your print bed so they come out correctly. If you use the brim version of parts, clean them up by pulling the brims off with pliers or snipping them off with angle cutters or even scissors. The brims are very thin.

Building the Robot

• STEP 1: Insert servos in the chassis. The wire coming out of the servo sticks out away from the robot, the servo shaft would face down toward the table top. As you insert the servo, slowly press it into place until it clicks in under the small tab on one side of the servo holder. Immediately mark the black connector at the end of the wire to indicate the servo number (which is engraved in the top of the servo holder, a number between 0 and 5). A metallic sharpie pen works very well for this, or an oil paint sharpie. Insert the 1-prong servo horn on the servo. DO NOT turn the servo shaft by hand, this can damage a new servo. Thread the wire through the top servo wire guide hole, and into the center of the chassis.

• STEP 2: Insert the servos in the Legs. The technique is very similar. Each leg has a large number on it, this is the leg number, they run from 6 to 11. Again, write this number on the black connector at the end of the servo wire. PRO TIP: For 6 and 9, underline the number so you don't read them upside down!

• STEP 3: Thread each leg servo wire into the bottom wire guide slot on the chassis. Each leg servo should be matched with a hip servo plus 6. For example, the leg marked 6 should be threaded through the wire guide on hip servo 0, leg 7 goes with hip 1, leg 8 goes with hip 2, etc. Add 6 to the hip number to get the leg number.

• STEP 4: Build the electrical system., You need to power up the servos and make them seek to the 90 degree position, this will allow you to adjust the legs properly for walking.
  • STEP 4A: Push the potentiometer shaft into the hole on the chassis meant for this purpose. The wires coming out of the potentiometer should be pointing down. Put the retaining nut on the potentiometer. Turn it all the way counter clockwise, then insert the knob so it points to STP.
  • STEP 4B: Put the on/off switch into the chassis, lining up the holes of the switch adapter with the two matching holes in the chassis. Insert a #6-32 1/2" screw from the outside and turn it to secure one side of the switch, repeat for the other side.
  • STEP 4C: Make the connections listed in the ELECTRICAL CONNECTIONS section of these instructions below. Be extremely careful about the power connections. Double check all connections before powering on.

• STEP 5: Power up! Make sure the on/off switch is off, and the knob is turned to STP. Connect a battery (6 x AAA rechargeable such as NIMH) and power on the robot using the on/off switch. The servos should all move. If the robot does not move at all, turn the switch off and check your connections again.

• STEP 6: Adjust Servo Horns. The servos are not at 90 degrees when the knob is all the way counter clockwise. turn the knob very slightly clockwise and you will see all the leg servos twitch. This is "adjust servo horn mode". All servos are now at their halfway point, 90 degrees. Now you need to take off each servo horn and adjust it so it comes straight out. Now, you will not always be able to make the horn come totally straight out. This is because there are only 22 little groves (splines) in each shaft, meaning you can in general only come within about 8 degrees of perfect. This amount of error is acceptable, just get it as close as you can. Do this for all hip and knee servos. Do not insert any screws yet.

• STEP 7: Attach Servo Brackets. The servo brackets connect the hips to the knees. They only go on one way. You need to very slightly bend the U shaped piece while inserting the bracket onto the servo. If you printed these parts using a brittle plastic, they may break, that's why we recommend PETG plastic for at least these pieces. (Usually ABS will also work, however it depends on the brand. PLA seems to be the most brittle of the commonly used 3D plastics and we don't recommend it for this part). First put the bracket on the hip servo (chassis) then the knee servo (leg).

• STEP 8: Test Knee Positions. Turn the knob fully counter clockwise (to STP) and the robot will go into "stand still" mode. Place it on a level surface such as a table top. Do all of the legs touch the ground? If one or more legs don't touch the ground, you need to adjust the servo horn on the knee a little bit so it does touch. Gently pull off the servo bracket. Pull the servo horn off, and put it back on just a little bit moved so the leg would move closer to the ground. Put the servo bracket back on, and see how it looks. Do this until all legs are at least slightly touching the ground. Again, you can't necessarily be perfect due to the 8 degree increments the servo horns can be moved. But you should be able to be close enough that all legs at least slightly touch the ground.

• STEP 9: Insert Servo Screws. Now that the legs are adjusted, you can insert the M2.5x8 screws into the servo horns to lock them in place. Note that you will NOT be using the screws that were in the little bag the servos came in, you'll be using the separate pack of screws, which are longer than the ones in the servo bag. Do not overtighten these screws, as you could possibly crack the servo brackets. Just turn the screws until you start to feel resistance, then turn a quarter turn more and stop.

• STEP 10: Test Individual Servos. To test whether every servo is working, put the robot on its stand. Then start with the knob on STP, then slowly turn it clockwise. First the servos will go into adjust mode, you used that a moment ago to set the servo horns. But, keep going, and the robot will go into "individual servo test mode". In this mode, every hip servo will move, one by one. When all the hips have moved, every leg will move, one by one. You should see every servo move, in order. If some don't move, check your connections. A common error is to plug a servo connector into the servo controller backwards (i.e. the brown wire is matched with the yellow pin instead of the black pin).

• STEP 11: Test Using Demo Mode. Ok, everything looks good, so time for a full test. Turn the knob to STP, then take the robot off the stand and put it on the floor. Turn the knob to DEMO, and the robot will go through a series of movements to demonstrate some of the things it can do. The full demo only takes about 30 seconds, then repeats. Here, you are looking for the robot to, for example, be able to get back up off the floor after doing some of its dance moves. If the robot struggles to get off the floor, you may have a battery that is not fully charged, or there may be too much friction between the servo bracket and the little ball socket it sits in. A tiny bit of silicone lubricant will usually fix that problem, or just make sure those parts are cleaned up from 3D printing and don't have an excess strands of material that are causing friction. See "Trouble Shooting" for more information about different kinds of issues that can occur.

Electrical Connections: Robot

NANO PIN CONNECTIONS

• Digital IO Pins:
  • D2 Bluetooth Module Rx
  • D3 Bluetooth Module Tx
  • D4 Beeper Signal (white wire)
• Analog Pins:
  • A0 Potentiometer signal (white wire)
  • A1 Potentiometer Power (red wire)
  • A2 Potentiometer Ground (black wire)
  • A4 Servo Controller SDA
  • A5 Servo Controller SCL

• Power Pins:
  • VIN From Battery positive (the red Dupont connector coming off near the switch on the wiring module)
  • GND From Battery negative (the black Dupont connector coming off the battery black wire)
  • GND (there are two GND pins on the Nano) goes to the GND pin on the HC06 module
  • +5V Goes to HC06 V+ Pin

IMPORTANT NOTE: The red Dupont connector must go to VIN and never +5V because the battery voltage is much higher than +5 volts. You will more or less instantly destroy your Nano if you put unregulated battery power directly into the +5V pin. The VIN pin has its own voltage regulator. The +5V pin on the Nano will be used to provide regulated power to the Bluetooth module.

Bluetooth Module Power

• V+ From the Nano +5V pin
• GND From either Nano GND pin

Beeper Power

• Connect the beeper V+ and GND pins to Port 14 of the Servo Controller, matching black and red wires to black and red pins on the Servo Controller.

Servo Controller

• Connect the 12 servos to port numbers corresponding to the servo marking (0 to 11). Make sure the signal wire (yellow) is oriented correctly.
• Connect the switch/battery module output to an unused servo port power and ground. Make sure the red wire is going to VCC and black wire to GND.
• On one short end you will find a VCC and VIN pin right next to each other. Use a shunt to connect those together. Both the servos and logic will run at +5V from the UBEC on the switch/battery module.
• SDA and SCL go to A4 and A5 on the Nano, respectively.

Electrical Connectons: Gamepad

NANO PIN CONNECTIONS

• D2 through D9 are connected to the button matrix pins.Looking from the top of the button matrix module, the rightmost button matrix pin goes to D9, second to right to D8, etc.
• D10 HC05 Tx
• D11 HC05 Rx
• A1 Dpad Signal (white wire)
• A2 Dpad VCC (red wire)
• A3 Dpad GND (black wire)
• VIN battery/switch positive (red wire)
• GND Either ground on the Nano goes to the battery/switch negative (black wire)

GAMEPAD: Screw Sizes

• Matrix button cover, 1/4" #6-32 screws (4)
• Yellow dpad buttons, 1/2" #6-32 screws (4)
• Gamepad Cover, 1" #6-32 screws (4)