The electronic board

Important: IT IS NOT MANDATORY

The only mandatory component is the ESP32-S3 which is a small board itself on which you can connect the servos.

Starting with PCB version 0.3, it's a modular solution, with the minimum of components to make the hand work, and then some pins allowing to plug extension cards, much like shields on Arduinos, to add capabilities.

All components can be soldered using a regular soldering iron, including the ESP32. There is no need to solder/connect the thermal pad underneath.

Depending on your ability with SMDs you can either solder C1 (SMD) or C2 (regular capacitor), do not solder both.

Some shield boards will be added soonish.

The main PCB

You can have the PCB made for a few euros by PCB makers. I have had only good experience with https://jlcpcb.com, they sent me 5 of these boards for $4.74 USD tax & shipping included (which converted to 4,52€ debited from my bank account through Paypal).

Use the provided gerber file, upload it to https://jlcpcb.com and pick the options you like. Some may have extra cost.

At some point I may have some PCBs available.

The components

List of components (WIP):

Quantity / Description

U3: 1 SEED Studio XIA ESP32 S3 (S3 is important, not C3)

C3: 1 capacitor 100µF 16V

C2 or C1: 1 capacitor 22nF

U1 & U2: 5 3-pin PCB screw terminals, or 1 3-pin and 2 6-pin or 1 3-pin and 1 12-pin They are optional but will make assembling easier. You need the 2.54mm kind.

1 5.5mm Power Jack for PCB

1 Power adapter delivering 6V and around 2 or 3A (very cheap ones may not work well because of sudden current needs)

J1: 1 10 pin header J2: 1 2x5 pin header

5 pin Jumpers for J1

Mounting the components

BEWARE: If you are building a left hand, the terminals, power jack, capacitors and pin headers should be mounted on the side of the PCB bearing the QR code, opposite to the ESP32.

The PCB shows the name of each component.

Before soldering the ESP32 you should plug it to a usb port and upload the firmware using Platformio. Check the wiki page about the firmware.

Make sure the ESP is working before soldering it to the PCB, because it's not easy to unsolder.

The screw terminals are not mandatory, you can solder the motor wires directly to the PCB. If you use the terminals, the space is pretty tight, but you can easily disconnect the motors, which is handy if recalibration is needed.

The pin headers J1 and J2 are not mandatory as well, if you are not going to use extension boards, but then, you need to connect the pads of J1 two by two:

Similarly, if you do mount pin header J1, but don't use any extension board yet, you will need to put jumpers on each pair of J1 pins:

Left and right hand PCB mounting (this is an earlier version of the PCB):

Mounting the PCB on the palm (right hand)

The PCB should be mounted with the ESP32 facing up, using 3 small screws M2.3x8 or similar

Mounting the PCB on the palm (left hand)

The PCB should be mounted with the ESP32 facing down.

The shields (Work in progress)

As of today, none are available.

You can easily build your own shields using prototyping PCBs, since the pin headers are aligned with a 2.54mm grid

J1 allows to insert some circuitry on the servo motor power lines, for instance to monitor the current and limit the grip.

J2 allows using 6 GPIOs from the ESP32, and also provide the VCC, 3.3V and GND.

Servo motor current monitoring

TODO

Oled screen

TODO

Myoelectric interface

TODO