FES Circuit Connection Guide

F

felix25062

Below is the updated, detailed pin-by-pin connection guide with a voltage regulator added to provide a stable 3V rail for the boost converter. This guide is designed for a beginner ECE engineer and includes all necessary steps and explanations.
Updated FES Circuit Connection with 3V Regulator Overview
This circuit consists of the following main blocks:
  1. Power Supply & 3V Voltage Regulator:
    • Provides a stable 3V rail from a higher voltage supply.
  2. Boost Converter:
    • Steps up the 3V rail to up to ~46V for stimulation.
  3. H-Bridge:
    • Converts the boosted DC voltage into biphasic pulses.
  4. Isolation Transformer & Electrodes:
    • Provides galvanic isolation for patient safety before delivering stimulation.
  5. Microcontroller (Arduino Nano):
    • Controls the circuit using PWM and digital signals.
  6. User Feedback:
    • Uses a potentiometer and an optional flex sensor.
1. Power Supply and 3V Regulator Section A. Power Supply Input
  • Input Source:
    • Use a DC power source (e.g., 5V, 7V, or 9V, depending on your design requirements).
  • Connection:
    • Connect the positive terminal of your supply to the input of the regulator.
    • Connect the negative terminal to the common ground.
B. 3V Regulator
  • Component: LM1117-3.0 or AMS1117-3.0 (3V LDO Regulator)
  • Pin Connections:
    • Input Pin: Connect to the positive terminal of the higher-voltage supply.
    • Ground Pin: Connect to common ground.
    • Output Pin: Provides a regulated 3V output.
  • Additional Components:
    • Place an input capacitor (e.g., 10 µF) between the regulator’s input pin and ground.
    • Place an output capacitor (e.g., 10 µF) between the regulator’s output pin and ground.
  • Result:
    • The regulator’s output (3V) is now available on the positive rail for the boost converter.
2. Boost Converter Section A. Key Components & Connections:
  • Inductor (4.422 mH):
    • One End: Connect to the 3V positive rail from the regulator.
    • Other End: Connect to the Drain (D) of the MOSFET.
  • MOSFET (NTD24N06L):
    • Drain (D): Connected to the inductor’s other end.
    • Source (S): Connect to ground.
    • Gate (G): Connect to Arduino Nano’s D9 (PWM output).
  • Flyback Diode (1N5819):
    • Anode: Connect to the MOSFET Drain (D) node (same as inductor output).
    • Cathode: Connect to the boosted output node (Vout).
  • Output Capacitors (2 x 100 µF, in parallel):
    • +ve Terminals: Connect to boosted output node (Vout).
    • -ve Terminals: Connect to ground.
  • Resistor (2.8 kΩ, across output):
    • Connect one end to boosted output (Vout) and the other end to ground.
This boosted voltage (up to ~46V, controlled by PWM duty cycle) will be used to power the H-Bridge.
3. H-Bridge (L298N) Section A. Powering the H-Bridge:
  • VCC of H-Bridge:
    • Connect to the boosted output (Vout, up to ~46V) from the boost converter.
  • GND of H-Bridge:
    • Connect to common ground.
B. H-Bridge Control:
  • Control Pins:
    • IN1: Connect to Arduino D5.
    • IN2: Connect to Arduino D6.
    • IN3: Connect to Arduino D10.
    • IN4: Connect to Arduino D12.
  • Enable Pins:
    • Tie both ENA and ENB to the boosted voltage (or directly to 5V if using internal logic, per your module’s datasheet) so that the outputs are always enabled.
C. H-Bridge Output:
  • Outputs (OUT1 & OUT2):
    • Connect each output through a 470 Ω resistor for current limiting.
    • The outputs then feed the primary winding of the isolation transformer.
4. Isolation Transformer & Electrode Section A. Isolation Transformer:
  • Primary Side:
    • Connect the outputs from the H-Bridge (after 470 Ω resistors) to the primary winding.
  • Secondary Side:
    • Connect the secondary winding outputs to the electrodes.
B. Electrodes:
  • Electrodes:
    • Connect one electrode to each secondary terminal.
    • These are applied to the patient’s limb.
5. Arduino Nano Control & Feedback Section A. Arduino Nano Power:
  • VCC:
    • Supply from a regulated 5V rail (if not using the same as the power source for the regulator).
  • GND:
    • Connect to the common ground.
B. PWM and Digital Control:
  • PWM for Boost Converter:
    • D9 (PWM Pin) → MOSFET Gate.
  • H-Bridge Digital Control Pins:
    • D5 → IN1 of H-Bridge.
    • D6 → IN2 of H-Bridge.
    • D10 → IN3 of H-Bridge.
    • D12 → IN4 of H-Bridge.
C. User Control Inputs:
  • Potentiometer (10 kΩ):
    • Center Pin: Connect to A0.
    • One End: Connect to 5V.
    • Other End: Connect to GND.
  • Flex Sensor (Optional):
    • One Terminal: Connect to 5V.
    • Other Terminal: Connect to A1 (with a 10 kΩ resistor from A1 to GND as a pull-down).
6. Summary of Signal and Power Flow
  1. Power Flow:
    • Higher Voltage Supply → 3V Regulator (LM1117-3.0) → Stable 3V Rail → Boost Converter (Inductor, MOSFET, Diode, Capacitors) → Boosted Output (~46V) → H-Bridge → Isolation Transformer → Electrodes.
  2. Control Flow:
    • Arduino Nano:
      • D9 (PWM) controls MOSFET in boost converter.
      • D5, D6, D10, D12 control H-Bridge to generate biphasic pulses.
      • A0 (Potentiometer) and A1 (Flex Sensor, optional) provide user input feedback.
  3. Safety:
    • 470 Ω Resistors limit output current.
    • Isolation Transformer provides galvanic isolation.
This comprehensive guide with the 3V regulator included should help you, as a beginner ECE engineer, build and develop the FES circuit. If you have any questions or need further clarification on any part of the circuit, please let me know!

flux

This is a comprehensive connection guide covering all the major blocks of your FES circuit. It’s very detailed and well organized, making it a great reference for building the schematic.
Would you like help translating this guide into schematic suggestions (such as adding components and wiring details) in your Flux project? If so, which block would you like to start with—for example, the 3V regulator section, the boost converter, or another part?
F

felix25062

Let's start with the 3V regulator block. Please add an LM1117-3.0 along with a 10 µF input and a 10 µF output capacitor, and wire them as described in the guide.

flux

Below is a summary of the schematic changes to add the 3V regulator block:
  • Regulator:
    • Add an LM1117-3.0 (designator [U1]).
    • Connections:
      • Input Pin: Wire to the positive input voltage (node "V_IN").
      • Ground Pin: Wire to the Ground.
      • Output Pin: Provides the regulated 3V output (node "3V_REG_OUT").
  • Input Decoupling Capacitor:
    • Add a 10 µF capacitor (e.g., C1) between [U1]'s input pin and Ground.
  • Output Decoupling Capacitor:
    • Add another 10 µF capacitor (e.g., C2) between [U1]'s output pin and Ground.
These connections follow the guide, providing a stable 3V rail from a higher voltage supply.
You can use the "Apply changes" button to update your schematic with these components and connections.
Add regulator block
Implement 3V rail
Configure regulator wiring
Set up 3V regulator
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