3 years ago

Fred's Left Hand Part 7

When you think of a hand, you tend to look at from the tips of the fingers back to the wrist.
But in the human hand, most of the muscles that drive the fingers are located in the forearm.
This is the same with the Inmoov robot.
So our journey we will start with the forearm.
This is convenient as I already have Fred's arm built down to his elbow on the left side.

In Part 1, I decided to use PTEG. For the forearm, most of it is a standard build except for the modified wrist.
In Part 2, I used a few nutserts and installed the servos.
In Part 3, I started on the version 2 hand its self.
In part 4, I installed the 5 Hall sensors and the springs.
In Part 5, I installed the electronics and the PTFE tube
The PTFE tube are 1.5mm ID and 2.5mm OD with the following lengths:
Thumb 335mm
Index 300mm
Middle 300mm
Ring 300mm
Pinky 360mm
In Part 6, I installed and wired the PCA9685.

In this part, I add the Elbow gear and connect all the tendons to the servos.

The 12 core ribbon wire used has the following wire assignments
1 - Servo Power - 6V
2 - Servo Power - 6V
3 - Servo Power - 6V
4 - I2C VCC - This is the I2C Bus power 5V
5 - I2C SDA - Serial Data
6 - I2C SCL - Serial Clock
7 - I2C Output Enable - Not Yet Used
8 - I2C Gnd
9 - Spare conductor for secondary I2C VCC
10 - Servo Gnd
11 - Servo Gnd
12 - Servo Gnd

The Spare I2C VCC on wire 9 is planning for the future.
The MPR121 is a capacitive touch sensor that would add to the ability of the hand to sense its environment, however it's max power supply is 3.5V, well below the Hall senors 4.5V minimum.
When MRL supports this chip, we can supply it with 3.3V and use the same SCL, SDA and Grd wires.
Up to 4 of these devices can be on the same I2C bus.

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