Battle Crab. Build Instructions. ALPHA Version

Battle Crab Build Instructions ALPHA Version Caveats: I built this robot as a learning project. It is not as polished as it could be. I accomplished my goal, to learn the basics, and kind of stopped. Improvement possibilities are abundant feel free to adjust to fit your needs. My models are adjusted to accommodate being printed on my older, home made 3D printer. For instance, I have to make holes a bit larger (.010 inches) in the model than they actually print. My printer is also rather poor at bridging, therefore many of my parts are split into separate pieces that I glue together after printing.

Setup/Operation: Pictured is how I setup my crab to the remote. Pick what buttons make sense to you, on your remote. Forward Moves both leg sets one step forward. Opposite for Rearward. Forward/Right Moves only the Right leg set one step forward. Similar function for the Forward/Left, Rearward/Right and Rearward/Left Functions. Pivot/Left Moves the Right leg set one step forward, and the Left leg set one step rearward. Opposite for Pivot/Right. Claw Pivot raises or lowers claws. The other functions are for trouble shooting/adjusting. Should be self explanatory I hope. Basic Step Operation For a single forward step, the crab uses the center leg servo to raise the right side of the crab off the ground, then moves the right leg set forward, lowers the right side back down and raises the left side, move the right leg set fully rearward, thus pivoting on the left center leg, then returns home and does the same with the left side leg set. FORWARD FORWARD LEFT FORWARD RIGHT Right Legs Home Forward Left Legs Home Rearward Left Legs Home Forward Increase Servo Delay Decrease Servo Delay Right Legs Home Rearward Center Legs Home Left Center Legs Home Right Center Leg Lift Increase Center Leg Lift Decrease PIVOT LEFT PIVOT RIGHT Forward/Left Forward Forward/Right Claws Up/Down Pivot/Left Pivot/Right Rearward/Left Rearward Rearward/Right REARWARD LEFT REARWARD RIGHT REARWARD

WARNING: Ifyou,likeme,arenewtoservomotors,manyhaveapreset function where they go through one full cycle, upon applying power, if no control signal is present. This robot has limited leg motion, and can t stand that servo motion without damaging the model or servo output shaft teeth. You must build the electronics and apply a control signal to the motors, BEFORE you attempt to power the motors. I ll explain as I go, but don t be tempted to turn on the power to the servos, before the electronics are running. Parts I used; Printed Parts; Shell Set Leg Set Body Set Electronics; Freduino Uno (Arduino Uno derivative. I only used this over the Arduino Uno because I had some lying around in the shop. I believe you could use the Arduino Uno interchangeably. I did not use any of the extended capabilities of the Freduino on this project) 1 DPDT Power switch. This can be any switch you like, you just may need to Adjust the hole in the body to fit your selection. 2 LEDs. Any color you like. 1 IR Sensor. (On the original crab, I used one from a dead DVD player. It worked great. I ended up buying some off ebay. They were 5 for $6.95. pretty cheap). The part number of the ones I bought are: Vishay TSOP 4838. (You can use most any, I guess, but you MUST determine the pinout of the device you use. They are NOT all the same. The one I pulled from the DVD player, I figured the pins by reading the traces on the pwb to which it was mounted. Since there are only three pins, if you find the power and ground, you know the signal. 1 100 Ohm, 1/8 or ¼ Watt Resistor. 2 220 Ohm, 1/8 or ¼ Watt Resistor. (These may need to be adjusted for the particular LED you select) 1.1 uf Capacitor. 4 SG90 Servo Motors. (I got 10 Tower Pro, Micro Servo 99s for $22.90 off ebay). 1 9V Battery Clip. 4 AA Batteries 1 9V Battery Wire For interconnecting, I used wire left from the servo wires, that were cut to fit. For the battery clips/connections, I used a strand from a heavier wire. The wire was approximately.028 inches in diameter. Connectors I used what I had laying around, some Molex connectors. There is no need to use connectors, unless you just want the shell halves to come apart. These could be done away with altogether. Hardware; I tried to keep the use of actual screws/nuts to a minimum, by using bits of heavy copper wire for many of the connections. The wire is 14AWG house wire, which has a diameter of approximately.060 inches. Screws to mount the servos came with them. 2 #4 40 x.75 long screws. 2 #4 40 x.50 long screws. 4 #4 40 x.38 long screws. 2 #4 40 nuts or nylok nuts. A bit of heavy thread or light fishing line.

Schematic; I wired it with connectors to be able to separate the shell from the body, but its not imperative. You do need to wire the Arduino board s ground to the motor ground.

Assembly; Start by printing out all the parts. In my part files (step, dwg or stl), I ve added anchor points to help avoid warping while printing. In the shell halves there is a support for the one overhanging piece. You should not need to add support when slicing. Clean all the edges, remove the anchor tabs, and any extra bits. Use the drill bits to clean up and size the appropriate holes as you go. Shell/Electronics; Cut the connectors off 3 of the servo motors, with about 3 inches of wire. Careful not to take too much (or too little). Pry up the pin retainer tabs, and slide out the pins. We ll use these to connect to the Arduino pins. If your Arduino doesn t have these type pins, well you ll figure something out. On the back of the IR sensor, wire the capacitor across the power and ground leads. Add the 100 ohm resistor to the power lead. Wire three of the contacts you removed from the servo motors to the sensor as shown.

Hot glue the LEDs in the eye holes. Following the schematic; Add a 220 ohm resistor to each LED. Wire the LED commons together. Add one of the servo contacts leads to each LED. Arduino Prep: Remove the power connector, careful not to damage the pwb. Add two ground wires, one for the LEDs and one to go to the Leg servos. Wire the positive lead of the battery clip to the Arduino pwb. Hot glue the IR sensor to the shell as shown. Hot glue the Arduino to the shell as shown. Connect one of the ground leads from the Arduino to the LEDs common connection. Using the contact leads from the servos, connect the arduino to the connector. You ll need to bend the contacts for the shell to mount to the body. At this point, plug the arduino into your computer, via the mini USB. Make sure the voltage switch is on 5V. Upload the sketch, and make sure the board still works. Use the serial monitor to see what s what. Now is the time to figure out your remotes buttons. Use the Arduino example sketch IRrecvDemo. Change the input pin (RECV_PIN) to 13, and change Serial.println(results.value, HEX); to Serial.println(results.value); to remove the HEX parameter. Upload the IRrecvDemo sketch to the crab, open the serial monitor and press the buttons you plan to use for your robot. Record which codes are which buttons and change the beginning of the BattleCrab sketch accordingly. You ll need to find the repeat code by holding any button, until you get a common code regardless of which button you press. Try it with different buttons by either holding the button down or pressing repeatedly very quickly. I found the Sony playstation remote was very erratic and never could get it to react reliably. Remotes act very differently, if these don t work for you, your on your own. I just figured this out myself, and on a limited set of remotes. If you have questions on this, Google is your best friend.

Body/Battery compartment. Add the wires that are the battery contacts. The ones at the front are just to short one battery to its neighbor. I put a bit of a kink in the wire to act as the actual contact. Adjust as necessary. Add the switch, and bend the tabs as shown or they hit the shell. Cut the two end tabs. Add a battery wire that bridges the two battery compartments. Use hot glue to hold and insulate the wire. Add a wire from each battery compartment to the switch as shown. Again, hot glue to hold and insulate.

Add the servo motors, using the hardware supplied with them. I found on my second crab that all servos are not the same. On my first crab, the wires exited the motor on a slanted edge, thus they installed into the openings easily. On the second crab, the wires exited the side wall of the motor, thus I had to remove the screws in the motor, feed the motor and wires thru the holes for the motor, them replace the motor cover. Add the center mount with the screws and nuts. Using the schematic, wire the servos to the connector. Save the connectors you cut off the servos, we ll need them shortly. Dress the wires and tack in place with some hot glue. Keep the wiring about as shown. Too much and you won t be able to get the shell on properly.

Add Levers to rear legs. Take the lever arms that come with the servo motors and find one that works best on the rear legs. It may have extra arms, just cut them off flush. Use a drill bit to enlarge the hole for the screw driver to be able to tighten the screw into the servo later on in the assembly. Match drill the holes on the lever, and wire it to the rear leg as shown. INSERT THE SERVO SCREW INTO THE LEVER BEFORE YOU WIRE IT TO THE LEG. Use bits of wire to connect the legs to the body. Notice the orientation of the center legs, their cross connector bar, and the servo that drives them. Install the screws into the front legs last. You may want to put a tiny bit of glue on the threads to stop them from coming loose during operation.

Claws; Thread the holes for the claw screws in the body to fit the screw you use. Screw the claws to the body. They should lift and fall easily. Use an appropriate lever from the servos, cut if necessary, and mount to the claw servo. Using the heavier copper wire. Create two loops, as shown, and press them into the holes on the body. You ll need to create notches in the shell for the thread to get to the claws. I used a soldering iron and just melted the notches in the shell. Using thread or fishing line, connect the claws to the servo level as shown. Add the swimmers on the back with two short screws. They should move freely, once installed. They keep the crab from flipping backwards. Hot glue the shell tips to the main shell. Connect the connectors and put the shell on the body, by inserting the tabs on the shell into the slots on the body. Be careful to tuck the wiring up, and try to get the connector to fall into the opening in the body.

Testing; You can connect the crab to your computer, just remove the 9V battery while you do it. Good way to test the crab, and make on the fly changes. While you are testing your crab, be mindful of a few things I learned the hard way; While connected to the computer, Do NOT upload a sketch, while the legs are turned on. This resets the motors. Never turn on the serial monitor, while the legs are turned on. This resets the motors. In both cases, you can turn off the legs, and the Arduino is still powered by the USB port and thus still works. So upload and turn on the serial monitor, THEN turn on the crab. And turn off the crab, BEFORE you do anything else. You ll notice in the sketch, there are buttons to adjust the leg homes and especially the center leg position and amount of step. I put them in to use during testing and calibration. You use them the first few times, then correct the sketch to match the changes, so you don t have to keep readjusting on each power cycle. I also put a speed control in the volume up/down buttons. This thing moves quite quick at full speed, but his traction is somewhat limited. So to limit the skittering, I slow it down. I also dipped the tips of the end legs in rubber coating to give it traction. If you make the legs rotation too large, the crab flips over easily. Just reduce the legs rotation in the sketch, or on the remote. The steps area bit clumsy and could be improved upon by someone with more time. The crab really doesn t Battle as much as push each other over backwards, and that takes a good bit of practice.