This chapter provides a complete list of components required for the MIDI Interface build.
The parts are organized into three categories:
- Voltage Regulation — components for generating and stabilizing the 5 V supply
- Logic and Signal Components — the optocoupler, Schmitt trigger, transistor, and supporting resistors
- Connectors and Indicators — MIDI jacks, LED, switch, and wiring harnesses
Use the subchapters below to view the detailed lists for each category.
Parts List (Grouped by Component Type)
🧩 Integrated Circuits
- 6N138 optocoupler
- Quantity: 1
- 74HC14 hex Schmitt‑trigger inverter
- Quantity: 1
- 78L05 voltage regulator (TO‑92 package)
- Quantity: 1
- Function: 5 V linear regulator, ~100 mA output
- Pinout (flat face toward you, leads downward):
- Pin 1: VIN
- Pin 2: GND
- Pin 3: VOUT (+5 V)
🔩 Transistors
- NPN transistor (2N3904, 2N2222, or equivalent)
- Quantity: 1
🛠️ Resistors
- 220 Ω resistors
- Quantity: 4
- Use: MIDI THRU current limiting
- 470 Ω resistor
- Quantity: 1
- Use: 6N138 VO → NPN base
- 10 kΩ resistor
- Quantity: 1
- Use: NPN collector pull‑up
- 1 kΩ resistor
- Quantity: 1
- Use: LED series resistor
🔋 Capacitors
Decoupling
- 0.33 µF capacitor (VIN → GND)
- Quantity: 1
- Type: Ceramic or electrolytic
- 0.1 µF capacitor (VOUT → GND)
- Quantity: 1
- Type: Ceramic
Bulk (Recommended)
- 10 µF electrolytic (input smoothing, VIN → GND)
- Quantity: 1
- Voltage rating: 16 V or higher
- 10 µF electrolytic (output smoothing, +5 V → GND)
- Quantity: 1
- Voltage rating: 10 V or higher
🔌 Connectors
- DC input connector (2‑pin or barrel jack)
- Quantity: 1
- MIDI IN connector (5‑pin DIN or harness)
- Quantity: 1
- MIDI THRU connectors
- Quantity: 4
💡 Indicators
- Standard LED (3 mm or 5 mm)
- Quantity: 1
🔧 Switches
- SPST power switch
- Quantity: 1
- Function: DC+ → VIN
🪛 Wiring and Headers
- Panel wiring for:
- MIDI IN
- 4× MIDI THRU
- LED
- Power switch
- DC input
- Optional: pin headers for removable harnesses
Bill of materials
| Category | Role | Component | Qty | Notes |
|---|---|---|---|---|
| Integrated Circuits | Logic and signal | 6N138 Optocoupler | 1 | MIDI IN isolation |
| Integrated Circuits | Logic and signal | 74HC14 Hex Schmitt Trigger | 1 | Signal conditioning (6 inverters) |
| Integrated Circuits | Power | 78L05 Voltage Regulator (TO‑92) | 1 | 5 V regulator, ~100 mA output,
|
| Transistors | Logic and signal | NPN Transistor (2N3904, 2N2222, MPS6514 or similar) | 1 | General‑purpose NPN transistor used for buffering and driving the LED indicator, MIDI out/thru driver |
| Resistors | Logic and signal | 220 Ω | 4 | MIDI THRU current limiting |
| Resistors | Logic and signal | 470 Ω | 1 | 6N138 VO → NPN base |
| Resistors | Logic and signal | 10 kΩ | 1 | NPN collector pull‑up |
| Resistors | Logic and signal | 1 kΩ | 1 | LED series resistor |
| Capacitors | Power | 0.33 µF (ceramic or electrolytic) | 1 | Regulator input decoupling |
| Capacitors | Power | 0.1 µF (ceramic) | 1 | Regulator output decoupling |
| Capacitors | Power | 10 µF electrolytic (16 V+) | 2 | Input and output smoothing |
| Connectors | Power | DC Input Connector (2‑pin or barrel jack) | 1 | Power input |
| Connectors | Logic and signal | MIDI Connector (5‑pin DIN or harness) | 5 | Input port, parallel thru outputs |
| Indicators | Power | LED (3 mm or 5 mm) | 1 | Power or activity indicator |
| Switches | Power | SPST Power Switch | 1 | DC+ → VIN |
| Wiring & Headers | Wiring | Panel Wiring | As needed | MIDI IN, 4× THRU, LED, switch, DC input |
| Wiring & Headers | Wiring | Optional Pin Headers | As needed | For removable harnesses |
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