BRAT Biped Mech PS2 Tutorial

- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-ps2-mech/WebHome/mechosf.zip">BRAT Servo Offset Finder Program</a>

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(09/17/09)

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- <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-ps2-mech/WebHome/bmech1-2.zip">PS2 Mech Control Code v1.2</a>

(11/11/2009)

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Image of Biped BRAT mech.</td>

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Overview: This tutorial will show

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how to build a BRAT-based mech using the hardware and components that we

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used in our build. This is NOT the only way to do a BRAT-based mech,

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though! Keep in mind that if you deviate from the components we used, you

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may have to make changes to the code we've provided, and the assembly

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instructions listed here may not match exactly. Have fun, and experiment!</td>

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<td valign="top" align="left">Step 1.

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Depending on how you've installed the aluminum channel on your BRAT, you

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may have to change it.

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For the Mech project, you'll need to make

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sure the aluminum channel is oriented as shown in Figure 1. If yours is

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different, you'll have to rebuild it.

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Figure 1.

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<td valign="top" align="left">Step 2.

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After rebuilding, make sure your bot looks like Figure 2. If it does, move

on to Step 3.</td>

Figure 2.

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<td valign="top" align="left">Step

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3.

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Attach an ASB-24 bracket to the aluminum channel as shown. Use 2-56 screws

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and nuts.

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The bracket will be off-center, but the

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servo horn will be center aligned.

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Figure 3.

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<td valign="top" align="left">Step

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4.

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Attach a suitable servo to the ASB-24; we used an HS-645. In our

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experience, the turret was a bit shaky with an HS-475 or HS-485.

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Remove the servo horn. This servo

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will rotate the gun platform turret. Plug the servo in to P11 on the Bot Board

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II. A wiring diagram is shown below.

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Figure 4.

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<td valign="top" align="left">Step

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5.

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For our gun platform turret, we used the add-on base rotate (ABR-01). A MPSH-01

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will support the camera, while a HUB-08 attached to ASB-06 will support

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the guns.

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Use 2-56 screws and nuts to attach the

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brackets as shown using the innermost holes. You will need to use a

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5/64" drill bit to add holes for the outermost screws as shown. Do

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this carefully! Make sure everything is aligned properly before drilling!

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Use 2-56 screws and nuts to attach the

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HUB-08s to the ASB-06s.</td>

Figure 5.

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<td valign="top" align="left">Step

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6.

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The guns we used can be purchased <a href="http://www.toyeast.com/v3/pdtdetail.asp?pdt_id=A02102961" target="_blank">here</a>.

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The website sells several versions of this gun. Make sure you get the

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"airsoft barrel mechanism" version, NOT the "IR barrel

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mechanism" version. Remember, if you use different guns, you may have to modify the code,

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and our assembly instructions may not work for you.

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Wiring instructions are shown in

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Figure 12. Don't worry about connecting the guns until you get there.

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We had to drill the center hole of the

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HUB-08s to .25" to accommodate mounting the guns we used. The gun's

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mounting posts have ridges that need to be filed or cut down, in order to

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fit into the HUB-08.

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We attached our guns to the HUB-08s using

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epoxy. Hold or clamp the gun tightly to the hub, and make sure to give it

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plenty of time to set before moving on.</td>

Figure 6.

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<td valign="top" align="left">Step

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7.

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Use the servo horn screw to attach the gun platform turret to the HS-645 servo.

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This completes the mechanical assembly.

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Because every servo is unique in its center position, we need to calibrate

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the software to the servos. To do this, follow the next steps.

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Figure 7.

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<td valign="top" align="left">Step

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8.

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Make sure your Bot Board is set up as shown in Table 8 and Figure 8.

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You MUST have the buttons enabled in

order to proceed.

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Bot Board I/O</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Connection</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Left Ankle</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Right Ankle</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Right Knee</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Right Hip</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Turret

Rotation</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0" colspan="2">Bot Board II

Jumper Settings</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Enable</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">A, B, and C buttons</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">I/O Groups 4-7 and 8-11</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Enable</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">SPKEN (Speaker Enable)</td>

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Table 8.</td>

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Figure 8.

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<td valign="top" align="left">Step

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9.

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Download and install the BASIC Micro Studio. Download the <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-ps2-mech/WebHome/mechosf.zip">BRAT Servo Offset Finder program</a>, and load it into the IDE.

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Program the Atom Pro, and follow these instructions to find your robot's offsets.

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<li>Press A to decrease the servo offset by 5us.</li>

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<li>Press C to increase the servo offset by 5us.</li>

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<li>Press B to change which servo is being manipulated, and to

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save your offsets. The order of the

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program is shown in Figure 9.</li>

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</ul>

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Note, if you have the Speaker enabled, when you press the B button you will hear a short tone. The tone will

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raise in pitch when you change from servo to servo, and will lower in pitch and be longer when you get back to Start.</td>

Figure 9.</td>

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<td valign="top" align="left">Step

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10.

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Place the robot in a position as close to neutral as possible, and turn it on. Your robot should go to and hold the neutral position, and should

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resemble figures 10-1 through 10-3. If the joints are off by more than 15° you may have made an error in assembly. To correct this, remove the

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center screw from the round servo horn, pull the servo horn off the servo, rotate until it's aligned, then reattach the servo horn.

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Use the A, B, and C buttons to straighten the BRAT as shown in Figures

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10-1, 10-2, and 10-3.

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Note, if you are building the robot with HS-422 servos, you will notice the hip servos oscillate if the robot

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is lifted off the ground. This is normal, and is due to the lower power servo. When the robot is walking, the effects are minimal. Using a

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voltage that is higher than 6vdc will make the oscillations worse. When building a robot with more powerful servos such as HS-475,

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HS-485, or HS-645, you

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will not see this effect.

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After you've cycled through the servos

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and adjusted them to match Figures 10-1 through 10-3, pressing the B

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button again will save your servo offset values to the Atom Pro's EEPROM.

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Figure 10-1.</td>

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Figure 10-2.

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Figure 10-3.</td>

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<td valign="top" align="left" colspan="2">Step

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11.

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Now download the <a href="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-bipeds/brat-biped-ps2-mech/WebHome/bmech1-2.zip">PS2 BRAT Mech Code

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v1.2</a>, load it into the

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IDE, and program your BRAT.

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<td valign="top" align="left">Step

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12.

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Now it's time to wire the guns up. This step will need to be done for each

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gun. Refer to Figure 12 for a wiring diagram. Use heat shrink at your

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discretion.

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The gun's black motor wire goes directly to ground.

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The red wire goes one side of the PicoSwitch. From the other side, run a wire from the PicoSwitch to +

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on the Bot Board II.

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For the motor's internal switch, cut a 24" servo extender cable in

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half and strip some from the end of the cable. Strip about a finger's width extra on the RED wire, and solder a 10k resistor onto the wire. Solder BOTH the yellow wire and the other end of the resistor to one side of the switch. Solder the black wire to the other side of the switch.

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Bot

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Board II</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">New

Mech Component</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">P16

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(AX0)</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Right

gun Picoswitch</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">P17

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(AX1)</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Right

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gun internal switch</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">P18

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(AX2)</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Left

gun Picoswitch</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">P19

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(AX3)</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Left

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gun internal switch</td>

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Table 12.</td>

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Figure 12.

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<td valign="top" align="left">Step

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13.

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The PS2 control commands are shown in Table 13.

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The command set has changed slightly from

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the one in the PS2 control tutorial. Make sure you read the list

carefully.

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">PS2

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Button</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Command</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Left

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Joystick</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Walk

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forward/backward and turn</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Right

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Joystick</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Aims

gun platform</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Return

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robot to home position</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Toggles

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switch connected to P0</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Shoot

with left gun</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Shoot

with right gun</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">D-pad

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Up</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Get

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up from face-down position</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">D-pad

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Down</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Get

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up from back-down position</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Start</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Enable/Disable

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robot's standby "rest" mode (enabled by default)</td>

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<td align="center" bordercolor="#808080" bgcolor="#C0C0C0">Select</td>

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<td align="center" bordercolor="#C0C0C0" bgcolor="#FFFFFF">Changes

stride length</td>

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Table 13.</td>

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<td valign="top" align="left">Step

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14.

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We used the <a href="http://www.trendnet.com/products/proddetail.asp?prod=145_TV-IP110W" target="_blank">TRENDnet

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TV-IP110W</a> camera. There are many choices as far as camera goes. You

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want a lightweight IP (NOT 2.4GHz) wireless camera.

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We removed the camera's outer casing to

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make it lighter, and used double-sided foam tape to attach it to the

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MPSH-01.

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Our camera is powered by a 7.4vdc LiPo

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battery with a 5vdc switching regulator.

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Figure 14.</td>

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<td valign="top" align="left">Step

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15.

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There are a lot of ways to make ammo holders. We found some tiny

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tupperware containers at a local dollar store, cut holes to match the

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guns, and use double-sided foam tape to secure them to the guns.

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Figure 15.</td>

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Wiki source code of BRAT Biped Mech PS2 Tutorial