Custom PCB Design for Arduino-Based Bionic Prosthetic Hand with 2× PCA9685, Myoelectric Sensor & Servo Power System Anyone

I am developing a bionic/prosthetic hand and forearm prototype and would like a quote for designing a compact custom PCB that integrates the main electronics of the system into a single board.
The objective is to replace the separate controller boards, power electronics and myoelectric sensor module currently used in the prototype with a more compact and professionally engineered integrated PCB.
The PCB should include:
- An Arduino-compatible microcontroller, with a straightforward method for uploading and updating my own software through the Arduino IDE. Direct USB programming is preferred if practical, together with an appropriate programming/recovery interface.
- Two PCA9685 16-channel PWM controller ICs, operating at separate I²C addresses, for servo control.
- Connections for approximately 22 servos in total. Some servos have been modified so that their internal potentiometer/position-feedback signals are externally accessible, and these feedback connections should be accommodated by the PCB.
- An integrated myoelectric/EMG sensing front end rather than relying on a separate external muscle-sensor module.
The external skin electrodes would connect directly to the PCB. I would like the PCB to contain the necessary low-noise analog circuitry for acquiring and conditioning the myoelectric signal before it is read by the microcontroller.
I would like your engineers to recommend an appropriate EMG architecture and suitable components. This may include, as appropriate:
- differential/instrumentation amplification;
- input protection;
- electrode bias/reference circuitry;
- analog filtering;
- gain stages;
- rectification/envelope detection if beneficial;
- appropriate ADC interfacing;
- and any other circuitry required for reliable myoelectric acquisition.
Low-noise performance is particularly important because the PCB will simultaneously operate a large number of servos. The EMG section should therefore be designed and laid out so that servo current transients, PWM activity, switching-regulator noise and digital circuitry do not significantly contaminate the muscle-signal measurements.
I am currently using a separate myoelectric sensor in the prototype and can provide its information and existing results as a reference, but the objective for this PCB is preferably to integrate the required myoelectric sensing electronics directly into the custom board.
Power system
The PCB will need appropriate power regulation and distribution for:
- the microcontroller;
- both PCA9685 ICs;
- the integrated EMG analog circuitry;
- other logic electronics;
- and the servo system.
The servos represent the major electrical load. I would like the power architecture designed using the actual battery specifications, servo operating voltages and servo current requirements that I will provide.
The design should account for:
- continuous servo current;
- transient and peak/stall currents;
- suitable voltage conversion/regulation;
- power-distribution copper requirements;
- thermal requirements;
- reverse-polarity and appropriate fault/overcurrent protection;
- bulk and local decoupling;
- appropriate grounding;
- and electrical separation/filtering between the high-current servo circuitry and the low-level EMG analog electronics.
Mechanical constraints
The PCB will be installed inside the forearm of the prosthetic arm.
The current target board envelope is approximately 78 mm × 40 mm, with approximately 5 mm desired clearance underneath the PCB. These dimensions are not completely rigid. If the required electronics cannot reasonably fit within this envelope, I can modify the surrounding forearm CAD.
I would prefer to establish the mechanical requirements early in the project.
An early PCB outline / preliminary STEP model should ideally show:
- PCB dimensions;
- mounting-hole locations;
- USB/programming-port location;
- battery/power connector locations;
- servo connectors;
- external potentiometer connections;
- EMG electrode connectors;
- and maximum component heights above and below the PCB.
This would allow me to continue designing the surrounding forearm structure while the detailed electronics are being completed.
Programming
I will develop and maintain the final prosthetic-hand control software myself. I am therefore not requesting development of the complete movement or gesture-control firmware.
I do require the board to be straightforward to program and reprogram through the Arduino IDE.
I would also value a simple hardware-validation program capable of verifying:
- the microcontroller;
- communication with both PCA9685 ICs;
- basic servo outputs;
- external potentiometer inputs;
- and acquisition of the integrated EMG signal.
Desired deliverables
- Editable schematic source files
- Editable PCB-layout source files
- Gerber and drill files
- BOM with exact manufacturer part numbers
- Pick-and-place / assembly files
- PCB STEP model
- Complete pinout
- Programming/bootloader information
- Arduino IDE configuration/upload instructions
- Hardware-validation/test program
- First-power-up and board-testing procedure
The initial production will be a small prototype run for engineering validation, but the design is intended to potentially progress toward repeat production. Component availability, manufacturability, reliability and suitability for future production are therefore important.
I can provide the current prototype photographs and wiring, Arduino implementation, existing myoelectric sensor information, forearm CAD, battery specifications, servo models/current requirements and information about the externally connected servo potentiometers.
For the quotation, please indicate:
- the proposed technical approach;
- what information you need from me before beginning;
- expected engineering stages/milestones;
- number of revisions included;
- estimated timeline;
- whether an early mechanical STEP model is possible;
- whether support during first assembled-board testing is available;
- and how design corrections discovered during prototype testing are handled compared with later feature changes requested by me. Is this a one-time project or a long-term hire?
Potential long-term collaboration.
This initial job is for the engineering and development of the first custom PCB for my bionic/prosthetic arm prototype. The immediate objective is to produce a reliable first revision, manufacture a small prototype batch, assemble it, and validate it physically.
However, I do not view this strictly as a one-time project. If the collaboration goes well, there may be continued work involving PCB revisions, integration improvements, additional sensors, future prosthetic-arm electronics, production optimization, and preparation for larger-scale manufacturing.
I would therefore prefer to work with someone who is interested not only in delivering the first PCB files, but also in potentially supporting future development of the system.
Work samples, sketches, photos, or files
I can provide supporting material including:
- photographs of the existing bionic-hand electronics and wiring;
- the current Arduino-based prototype;
- photographs of the two PCA9685 servo-controller boards currently being used;
- forearm and internal structural CAD/STEP files;
- approximate PCB-placement location inside the forearm;
- existing wiring/circuit diagrams;
- servo specifications;
- battery specifications;
- information about the servos modified to expose their potentiometer feedback;
- information and photographs of the myoelectric sensor currently used as a reference;
- and my existing Arduino code if useful for understanding the required connections.
The new PCB does not need to reproduce the current arrangement exactly. The existing system is primarily a functional prototype and reference.
The goal is to redesign these functions into a properly engineered integrated PCB, including the Arduino-compatible controller, two PCA9685 sections, servo/potentiometer interfaces, power electronics, and preferably the myoelectric/EMG analog front end directly on the PCB.
I can provide additional measurements, photographs or CAD information during the design process as required.
Timeline
I am flexible regarding the overall project duration.
I would rather have the PCB engineered and reviewed properly than impose an unnecessarily short deadline. A reasonable engineering schedule of approximately 2–4 weeks for the design stage would be acceptable, although I am open to the designer's recommendation after reviewing the scope.
One part of the schedule is particularly important:
I would like the preliminary mechanical PCB definition early in the project, ideally before the complete electrical layout is finished.
This should establish approximately:
- PCB length and width;
- mounting-hole locations;
- major connector positions;
- USB/programming-port position;
- power connector position;
- EMG electrode connector position;
- servo connector positions;
- and maximum component heights.
Once these dimensions are sufficiently stable, I can continue designing and manufacturing the surrounding forearm structure while the PCB engineering is completed.
I therefore care more about an early mechanical milestone and thorough final validation than an unusually fast final delivery.
Budget
I am currently obtaining several professional quotations before selecting the designer/manufacturer.
For independent PCB-design services I have received offers around $200–$450 USD, depending on the exact scope, revisions, engineering support and deliverables.
However, I would prefer not to artificially constrain CADworks to those quotations. I would like you to evaluate the actual engineering requirements and provide your own itemized quotation.
Please separate, where applicable:
- schematic/electrical engineering;
- PCB layout;
- EMG analog-front-end development;
- power-system engineering;
- mechanical/STEP integration;
- design reviews and revisions;
- prototype fabrication;
- component procurement;
- PCB assembly;
- first-board testing/bring-up;
- and post-delivery engineering support.
I am willing to pay more for a technically stronger solution if the additional cost corresponds to meaningful engineering, validation, reliability, documentation, and support.
My priority is not simply obtaining the cheapest PCB. The board controls a prosthetic system containing multiple servos and a sensitive myoelectric interface, so I want the first design to be approached carefully enough that the power system, analog sensing, programming architecture, and mechanical integration are all properly engineered.
For the initial stage, I would like a complete quotation before committing, including the expected milestones, revision policy, deliverables and any costs that would be separate from the quoted engineering fee. read less