MeArm: Assembly

Parts

You need to following parts (this list might be inaccurate)

• Laser cut parts made from MDF sheets

• 2 Servo Motors Large S3003 with flat two armed plastic insert for axle

• 2 Servo Motors  Small SG90, with flat two armed plastic insert for axle, we have two kinds of these motors and the plastic inserts differ (white versus black)

• 10 x M3 Nuts

• 7 x M3 Screws 6mm long

• 15(-8) x M3 Screws 8mm long

• 3(+8) x M3 Screws 10mm long

• 8 x M3 Screws 12mm long

• 4 x M3 Screws 20mm long

• You will also need small short screws to attach the plastic inserts from motor axel to the wood pieces (two each).

• Each motor has screws to attach the plastic insert to the axle, screws for small motors don't fit the large ones. 

  • I count following mounting hardware

    • 2 black axle plastic pieces (2 armed) with 2 mounting screws (black) and 4 thin screws fitting into the axle pieces

    • 2 white axle plastic pieces (2 armed) with 2 mounting screws (reflective) and 4 thins screws fitting into the axel pieces. Two more of the thin screws to mount one motor on plate.

    • Some motors have machined axle thread and you need other mounting screws for those.

    • Please check if the plastic piece fits your motor axle and that the axle screw is small and large enough.

References

PWM driver specifications: https://cdn-shop.adafruit.com/datasheets/PCA9685.pdf

Dual H Bridge driver specifications: https://cdn-shop.adafruit.com/datasheets/TB6612FNG_datasheet_en_20121101.pdf

PWM Header pin is channel #14, #15, #1, #0, 5V and GND is available on the board's right side. Some boards have S,V,G connectors and don't need that you create connections to power and PWM signal. G is ground and the brown colored cable on the servo motor. Make sure you produce the correct connections for the motor cables on the development space if you not already have a connector for the servo motors on your board. Read the specifications of the cable on the item 1) in above sparkfun tutorial, making sure you do not plug them in backwards.

Manual

In the PDF manula below, only the assembly illustrations are relevant. The manual is not made for the Motorhat we use in BME210. The software instructions are not relevant to our setup.

Assembly Instructions for MeArm 

The PDF above gives you the assembly instructions. Skip the Arduino Section and the Code Section.

The parts for the MeArm will need to be cut from 1/8 inch sheets.

WARNING:

When mounting the plastic piece onto the motor axel it will need to have proper orientation. It does not need to be accurate but you will need the full range of motion.

Some motors have defined end positions which you can test without energizing the motor. All motors rotate +/- 90degrees.

You can use the calibrate.py program to set the motor either to the center (1250) [500 min, 2000 max,, 1250 center]

(1) Base

For the Base you want the turret to be able to be mounted pointing forward (big opening in the base plate). The you need to make sure the turret can rotate -90 and plus 90 degrees from that position. It should look like picture 1 below.

(2) Left Elbow

The elbow is the most difficult to adjust because once the axle screw is mounted you can no longer reached it with a screw driver.

You will want to be able to rotate the axle so that the wood extension collides with the bottom of the turret and in the other directions it should move the plastic piece to a vertical position. (3) 

(3) Right/Shoulder

The axle screw can be reached and adjusted later if needed. The sholder you will want to be able to move so that the claw is all the way extended forward and can retracted to touch the turret.

(4) Claw 

The claw you want to be able to open and close. The adjustments are less critical and you can take out the axle screw. 

When you connect the motors to motor hat please use the following slots:

Base Motor: Channel 0

Shoulder Motor: Channel 1

Elbow Motor: Channel 14

Claw Motor: Channel 15

Assembly Pictures