Important: For a student prototype, keep the power stage low-voltage DC, for example 12 V or 24 V. Do not directly switch household AC mains unless supervised by a qualified person and using certified protection hardware.

Diagram

1. Renewable input: solar panel or current-limited bench supply.
2. Battery input: 12 V or 24 V battery with BMS.
3. Grid input: isolated AC-DC adapter or bench supply representing grid backup.

• Beginner-safe: 12 V DC
• More realistic but still manageable: 24 V DC

• High-side resistor from measured rail to ADC input
• Low-side resistor from ADC input to ground
• Small capacitor from ADC input to ground for noise filtering
• Optional Schottky or TVS clamp for ADC protection

• Rtop: 100 kOhm
• Rbottom: 27 kOhm
• ADC voltage at 15 V input: about 3.19 V
• Filter capacitor: 100 nF from ADC node to GND

• Use logic-level N-channel MOSFETs for low-side switching of DC loads.
• Use high-side switches or relays for source selection.
• Add flyback diodes across relay coils.
• Add gate resistors and pull-down resistors on MOSFET gates.
• Fuse the battery path.

• PV voltage and current
• Battery voltage and current
• Load voltage and current
• Battery temperature
• Grid adapter availability

• Battery charge/discharge enable
• Grid input enable
• Load priority switches
• Status LEDs
• Communication dashboard

Diagram

• PV power: P_pv = V_pv * I_pv
• Load power: P_load = V_bus * I_load
• Battery power: P_batt = V_batt * I_batt
• Battery state of charge estimate
• Time-of-use electricity price
• Grid availability
• Battery temperature

1. If PV power is greater than load demand:
   • Supply load from PV.
   • Charge battery if battery is not full.
   • Disconnect grid input.
2. If PV power is less than load demand and battery state of charge is healthy:
   • Use battery to support the load.
   • Keep grid disconnected unless bus voltage falls.
3. If battery state of charge is low:
   • Disable battery discharge.
   • Use grid adapter to supply load.
4. If electricity price is low:
   • Optionally charge battery from grid.
5. If electricity price is high:
   • Prefer PV and battery.
6. If bus voltage is unstable:
   • Shed noncritical loads.
   • Enable grid backup.

Text
loop every 1 second:
    read voltages, currents, temperature
    calculate PV power, load power, battery SOC

    if fault detected:
        disconnect battery discharge
        disconnect noncritical loads
        enable safe mode

    else if PV_power > load_power:
        grid_switch = OFF
        load_switch = ON
        battery_charge = ON if SOC < 95 percent

    else if SOC > 30 percent and battery_temperature_ok:
        grid_switch = OFF
        battery_discharge = ON
        load_switch = ON

    else:
        battery_discharge = OFF
        grid_switch = ON
        load_switch = ON

    log data
    update dashboard

1. Define bus voltage, battery voltage, and load power.
2. Build the controller on a breadboard or development board.
3. Use bench supplies instead of real solar and battery initially.
4. Connect voltage dividers to ADC pins.
5. Connect current sensors.
6. Add relay or MOSFET modules for switching.
7. Write firmware to read sensors and log data.
8. Implement manual switching mode.
9. Implement automatic rule-based dispatch.
10. Test with small DC loads.

1. Add solar panel or solar simulator input.
2. Add MPPT charge controller.
3. Add battery pack with BMS.
4. Add fuses and emergency disconnect.
5. Test charge and discharge separately.
6. Verify battery never charges/discharges outside safe limits.

1. Add electricity price schedule.
2. Add forecast input, such as expected PV generation or load demand.
3. Implement a cost function:
   • Minimize grid energy cost
   • Penalize battery overuse
   • Penalize bus voltage deviation
   • Keep reserve battery SOC
4. Compare rule-based control vs optimized control.

1. Convert the prototype circuit into a schematic.
2. Select exact MPNs and read datasheets for each IC/module.
3. Add footprints, protection, and connectors.
4. Set PCB stackup and design rules.
5. Place power components close together.
6. Keep high-current paths short and wide.
7. Separate noisy switching nodes from ADC sensing traces.
8. Run ERC/DRC.
9. Export Gerbers, BOM, and pick-and-place files.

1. DC bus voltage: 12 V or 24 V.
2. Maximum load power: for example 20 W, 50 W, or 100 W.
3. Battery chemistry and voltage: for example 3S Li-ion, 4S LiFePO4, or 12 V lead-acid.
4. Whether the prototype should use ready-made modules or custom IC-level circuits.
5. Communication preference: WiFi, Bluetooth, USB serial, or no wireless.
6. Whether the load output is DC only or you eventually need AC inverter integration.

• 12 V DC bus
• 20 W to 50 W load
• 12 V battery with built-in BMS
• ESP32 or Arduino-class controller
• Ready-made MPPT, buck, relay/MOSFET, and current-sensor modules
• Custom PCB only for the controller, sensing, and signal-level switching first