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This modular precision resistance decade provides 17 adjustable resistance stages from 10 Ω to 2 MΩ, using high-quality 25-turn Bourns trimmers mounted on a custom PCB. Ideal for analog testing, calibration workflows, and educational labs, this decade design emphasizes modularity, clarity, and reliability — perfect for engineers, experimenters, and machine logic hobbyists.
- 📄 Bill of Materials (BOM) – Complete list of components and values
- 🖼️ Circuit Schematic (PNG) – Visual overview of the circuit
- 🧪 Gerber Files – PCB production files
- 🔁 17 resistance stages from 10 Ω to 2 MΩ
- 🎚️ Bourns precision potentiometers (25-turn, 0.5 W, max 900 V)
- 📌 Summed output and single-value taps for each stage
- ⚡ Up to 100 mA load capacity per trimmer (varies by stage)
- 🧰 Direct pinheader access to each tap & screw terminal for summed output
- 📐 KiCad layout with clean ground routing and logical spacing
- 🪛 Mountable grid PCB for breadboard alignment & enclosure integration
- 🖨️ Clearly labeled silkscreen with nominal values and tap references
- 🔓 Licensed Open Hardware (CERN-OHL and CC-BY-SA)
- Sensor calibration and analog simulation
- RC circuit prototyping and pulse shaping
- OpAmp testing with predictable resistance
- PWM-based analog filter loading
- Reference resistor in microcontroller or LabVIEW experiments
- Machine logic debugging and voltage divider tuning
| Attribute | Value |
|---|---|
| Resistance Range | 3.8 Ω – ~3.93 MΩ measured (nominal 10 Ω–2 MΩ) |
| Adjustments | 25-turn linear Bourns trimmers |
| Tolerances | ±10% trimmer tolerance (nominal), plus measured deviation |
| Max Voltage | 900 V DC across stages |
| Power Dissipation | 0.5 W max per potentiometer |
| PCB Size | Grid-compatible (standard mounting) |
| Output Taps | Individual tap headers + summed terminal |
| Tap | Nominal Value | Measured Min | Measured Max |
|---|---|---|---|
| R10 | 10 Ω | 0.1 Ω | 13.8 Ω |
| R20 | 20 Ω | 0.1 Ω | 22.4 Ω |
| R50 | 50 Ω | 0.1 Ω | 53.3 Ω |
| R100 | 100 Ω | 0.1 Ω | 105 Ω |
| R200 | 200 Ω | 0.1 Ω | 197.1 Ω |
| R500 | 500 Ω | 0.1 Ω | 507.1 Ω |
| R1K | 1 kΩ | 0.3 Ω | 1.014 kΩ |
| R2K | 2 kΩ | 1.3 Ω | 1.953 kΩ |
| R5K | 5 kΩ | 0.1 Ω | 4.656 kΩ |
| R10K | 10 kΩ | 0.1 Ω | 9.830 kΩ |
| R20K | 20 kΩ | 0.1 Ω | 19.840 kΩ |
| R50K | 50 kΩ | 0.1 Ω | 49.400 kΩ |
| R100K | 100 kΩ | 0.3 Ω | 108.000 kΩ |
| R200K | 200 kΩ | 0.2 Ω | 201.500 kΩ |
| R500K | 500 kΩ | 0.1 Ω | 491.600 kΩ |
| R1M | 1 MΩ | 0.3 Ω | 960 kΩ |
| R2M | 2 MΩ | 0.3 Ω | 2.083 MΩ |
🔁 Total summed output measured: ~3.8 Ω – 3.93 MΩ
🧠 Note: Slight deviations due to trimmer tolerance, contact resistance, temperature drift. No calibration applied — raw measurement data.
- 🔍 For highest precision: use low current during measurement, and 4-wire Kelvin sensing where possible
- 📎 Tighten taps with clean leads or clipped headers for minimal contact noise
- 🔧 Use active load or microcontroller ADC for dynamic feedback calibration
- 🧪 When combining multiple stages, consider total series resistance and parasitics
- 🌡️ Keep temperature stable to avoid thermal drift in high-ohm ranges
- Grid-aligned mounting holes
- Ground plane continuity with star output topology
- Silkscreen identifiers for each trimmer + tap point
- Clear trace widths and pad spacings for easy soldering and rework
This project is licensed as Open Hardware under the
- Hardware (schematics, layouts, power) CERN-OHL-P v2 for (schematics, layouts, power)
- Documentation (Markdown, diagrams) Creative Commons Attribution ShareAlike
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