BRAT Biped Assembly Guide

Last modified by Eric Nantel on 2024/07/03 09:21

Biped BRAT Assembly Guide

Updated May 2015

Safety first! Wear eye protection and never touch a powered robot!

This guide applies to the following versions of the BRAT biped:

BRATCB: BRAT Combo Kit - Bot Board 2
BRATCC: BRAT Combo Kit for PC - Bot Board 2
BRATCBU: BRAT Combo Kit (Autonomous) - BotBoarduino
BRATCCU: BRAT Combo Kit w/ BotBotboarduino
BRATCFB: BRAT Combo Kit (FlowBotics Studio) - SSC-32 or SSC-32U
BRATCA: BRAT Combo Kit for PC w/SSC-32 or SSC-32U

Important! To assemble the BRAT robot, construct a right leg (following the pictures on the right), and a left leg (by following the pictures on the left)! Keep in mind that the pictures marked "Right Leg" are the robot's right leg. After the legs are constructed, the images will no longer be split.

Image of completed robot.

Figure 1. (Left Leg)

Step 1.
Attach a multi-purpose bracket to the foot as shown, using three 2-56 x .125" screws and 2-56 nuts each.

6 x	6 x

Figure 1. (Right Leg)

Figure 2. (Left Leg)

Step 2.
Attach the "L" bracket to a short "C" bracket as shown, using two 2-56 x .250" screws and 2-56 nuts each.

4 x	4 x

Figure 2. (Right Leg)

Figure 3. (Left Leg)

Step 3.
Attach a multi-purpose bracket to the "L" bracket as shown, using two 2-56 x .250" screws and 2-56 nuts each.

4 x	4 x

Figure 3. (Right Leg)

Figure 4. (Left Leg)

Step 4.
Attach the assembly from Step 3 to the multi-purpose bracket on the foot. See figure 4-1 for detailed information.

Figure 4-1.

Figure 4. (Right Leg)

Figure 5. (Left Leg)

Step 5.
Connect two short "C" brackets as shown, using two 2-56 x .250" screws and 2-56 nuts each.

4 x	4 x

Figure 5. (Right Leg)

Figure 6. (Left Leg)

Step 6.
Attach the "C" brackets to the leg assemblies as shown. See figure 6-1 for detailed information.

Figure 6-1.

Figure 6. (Right Leg)

Figure 7. (Left Leg)

Step 7.
Attach a multi-purpose bracket to the "C" bracket as shown. See figure 7-1 for detailed information.

Figure 7-1.

Figure 7. (Right Leg)

Figure 8. (Left Leg)

Step 8.
Attach the leg assembly from step 7 to the 3" U-Channel as shown, using three 2-56 x .250" screws and 2-56 nuts on each side.

6 x	6 x

Figure 8. (Right Leg)

Step 9.
Your assembly should look like the image so far. Note, in the image the robot is face down. Note that since we now have a single object to work with, we will be proceeding with a single image from here on.

Figure 9.

Step 10.
Install the two ankle servos as shown, using the included 3mm hardware, two #2 tapping screws, and the diagram below. Note, your servos may be a little off. We will fix this in software later.

4 x

Figure 10.

Step 11.
Install the knee and hip servos as shown. Use the #2 tapping screws and the diagram below.

8 x

Figure 11.

Step 12a (SSC-32 / SSC-32U).
Note that the optional PS2 receiver is only compatible with the BotBoarduino and old Bot Board 2. Follow this step if you have the SSC-32 / 32U or do not have or plan to mount the PS2 receiver.

Attach the 3/4" standoffs to the electronics carrier using four 4-40 x 1/4" hex socket head cap screws.

4 x	4 x

Figure 12a.

Step 12b (Optional PS2 Receiver).
Note that the optional PS2 receiver is only compatible with the BotBoarduino and Bot Board 2. If you have the SSC-32 or SSC-32U, or do not plan to use the PS2, follow step 12a.
Follow this step if you have the BotBoarduino or Bot Board 2 AND plan to mount the optional PS2 receiver plate / PS2 receiver.

Attach the 1/2" standoffs to the electronics carrier using four 4-40 x 1/4" hex socket head cap screws.

Note that some images in the steps below will show the 3/4" spacers mounted to the carrier; your version however will have the 1/2" spacers.

4 x	4 x

Figure 12b.

Step 13.
Attach the 5/16" standoffs to the U-Channel as shown, using two 2-56 x 1/4" screws.

2 x	2 x

Figure 13.

Step 14.
Attach the electronics carrier assembly as shown, using two 2-56 x 1/4" screws.

2 x

Figure 14.

Step 15.
To prevent the wires from tangling, you will want to secure them as shown. This can be done with wire ties or similar, not included.

Make sure that the ankle servo is positioned as shown when securing the wires to ensure the full range of motion is available.

Figure 15.

Step 16.
Attach the battery power switch to the electronics carrier as shown. We suggest tape, tie-wraps or other similar method.

Figure 16.

Step 17a (SSC-32 / SSC-32U / Bot Board 2 ).
Install the electronics (SSC-32, SSC-32U, Bot Board II) using four 4-40 x 1/4" screws.

It is best to orient the board with the screw terminas at the bottom of the robot.

If using a Bot Board II, go ahead and install the BASIC Atom Pro 28 chip as well in the orientation shown below.

Note that if you are using the optional PS2 mounting plate, you should follow that guide and use 1" M/F standoffs instead.

4 x	Atom Pro Orentation

Figure 17 (Bot Board 2, SSC-32, SSC-32U).

Step 17b (BotBoarduino).
Install the BotBoarduino microcontroller using four 4-40 x 1/4" screws. It is best to orient the board with the connection to the computer (USB) and screw terminals facing the top.

Note that if you are using the optional PS2 mounting plate, you should follow that setup and use 1" M/F standoffs instead of the 4-40 x 0.25" screws below. At this point you can also mount the PS2 receiver to the Lexan PS2 mounting plate using the four screws provided. This involves removing the existing screws on the receiver and using the screws provided to mount it to the Lexan.

4 x

Figure 17b (BotBoarduino).

Step 18.

In preparation for connecting the power wires, here are some general guidelines when inserting multistrand wires into screw terminals. Use a ~2mm wide flat blade screw driver. Rotate the screw both directions looking into the end of the terminal. When you see it open up (moving downwards), keep turning until it is open completely. Wrap / twist the wires by hand to ensure they are aligned as in Figure 6. Be sure that the wires are fully inserted into the terminals and that no stray wires touch each other between terminals as this is a short and can cause the battery to discharge rapidly, causing heat and possibly fire. DOUBLE CHECK THE RED AND BLACK WIRE CONNECTED TO THE SCREW TERMINALS - the red wire should go to (+) and the black wire to (-), if they are reversed, the servos and the board will be damaged.

Figure 18 (Top shows open, bottom shows closed).

Step 19a (SSC-32 / SSC-32U / Bot Board 2).

Connect the battery wiring harness to VS1 on the SSC-32 / SSC-32U or VS on the Bot Board II. Note, red is (+) and black is (-).For the SSC-32 / 32U, leave the VL = VS jumper in place (as well as the VS1 = VS2 jumpers). Connect the servos to their appropriate I/O channels on the board using the table below, and make sure to check your work. Please note that on table 19a, pin 10 is NOT a typo; pin 9 is used on the Bot Board II for the speaker.

SSC-32 / 32U I/O	Servo	Bot Board II I/O
00	Right Ankle	07
01	Right Knee	08
02	Right Hip	10
16	Left Ankle	04
17	Left Knee	05
18	Left Hip	06

Table 19a.

Figure 19a (SSC-32 as example).

Step 19b (BotBoarduino).

Connect the wiring harness to EITHER VS or VL on the BotBoarduino. Leave the VL = VS jumper in place. Note, red is (+) and black is (-). Connect the servos to their appropriate I/O channels on the board using the table below, and make sure to check your work.

BotBoarduino Digital I/O	Servo
10	Right Ankle
11	Right Knee
12	Right Hip
02	Left Ankle
03	Left Knee
04	Left Hip

Table 19b.

Figure 19b (BotBoarduino).

Step 20a.

If you have the 6V, 1600mAh NiMh battery, note that it fits nicely inside the U-Channel. You can then secure it in place with zip-ties.

Figure 20a (1600mAh Battery).

Step 20b.

If you have the 6V, 2800mAh NiMh battery (or other 6V battery), we suggest placing it on top of the U-channel and securing it in place with zip-ties.

Figure 20b (2800mAh Battery).

Step 20.
For controlling this robot with the just the SSC-32 and Sequencer, you can now move to the Sequencer tutorial.

For controlling this robot with the SSC-32U and FlowBotics Studio, please install and open FlowBotics Studio and follow the instructions.

For those using a Bot Board II, you can now move on to the Autonomous, Water-Bottle Kicking, or PS2 tutorial.

If you have a BotBoarduino, you can move on to the BRAT + BotBoarduino + PS2 tutorial.

Note that there is currently no sample code available for autonomous behavior using the BotBoarduino.

Figure 20.

Step 21 (Optional PS2 Receiver).

If you have the optional PS2 receiver and mounting plate, figure 21 shows you what the final robot will look like. You can mount the PS2 Lexan + receiver assembly using four 4-40 x 1/4" screws. Note again that the PS2 receiver only works with the Bot Board 2 or BotBoarduino versions of the BRAT kits.

Figure 21.

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Created by Eric Nantel on 2024/07/03 09:21

BRAT Biped Assembly Guide

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