Unit 2 — Construction and Materials
TM-GEAR-006 — Open Handout TM Chapter: Chapter 3 ELOs: Identify required components and materials; understand component selection criteria Estimated time: 20 minutes
Step 1: Read the TM
Open TM-GEAR-006. Read Chapter 3 — Equipment and Materials completely.
Then come back here.
Chapter 3 Content
| Component | Spec / Part | Purpose |
|---|---|---|
| Spindle motor | NEMA 23, 2.5A, 200 steps/rev | Rotate winding former |
| Traverse motor | NEMA 17, 1.5A, 200 steps/rev | Advance wire guide |
| Spindle driver | TMC2208 or A4988 | Microstepping drive |
| Traverse driver | TMC2208 or A4988 | Microstepping drive |
| Controller | ESP32 WROOM-32 | Step generation, UI, SD logging |
| Display | SSD1306 0.96” OLED I2C | Turn counter, speed, status |
| Encoder | KY-040 rotary encoder + button | Parameter entry |
| SD card module | SPI, 3.3V | Winding program storage |
| Power supply | 24V 5A (or 12V for NEMA 17) | Stepper VMOTs |
| Limit switches | 2× microswitches on traverse | Home and end-of-travel |
Component Selection
Review the equipment and materials list in Chapter 3 carefully.
Before building, verify every item on the materials list. Key considerations: - Use the specified component types — substitutions may affect performance or frequency coverage - Non-inductive components are required in RF circuits; standard wirewound resistors are unsuitable - Toroids and ferrite cores are frequency-specific; use the specified core material (#43, #61, #67, etc.) - Connector types affect impedance — match the specified connector to avoid SWR errors - Wire gauge and insulation type affect current capacity and voltage breakdown
The quality of your materials sets the ceiling on the component's performance.
Self-Check Questions
SC2-1. List the three most critical components or materials specified in Chapter 3. Why are they critical?
SC2-2. Does Chapter 3 specify non-inductive resistors? If so, where are they used and why does it matter?
SC2-3. What connector type(s) does Chapter 3 specify, and what is the frequency/power justification?
SC2-4. Does Chapter 3 specify a particular ferrite core material or type? What is its significance?
SC2-5. What would be the consequence of substituting a standard wirewound resistor for a non-inductive type in an RF application?
Answer Key
SC2-1. See Chapter 3. Identify items with specific part numbers, special materials, or critical tolerances — these are the ones that most affect performance.
SC2-2. See Chapter 3. Non-inductive types are used wherever standard inductive wirewound resistors would add series inductance that degrades high-frequency performance.
SC2-3. See Chapter 3. SO-239, N-type, BNC, and SMA each have different frequency and power ratings.
SC2-4. See Chapter 3. Ferrite #43 is for 1–100 MHz; #61 for 10–200 MHz; #67 for 50–500 MHz. Wrong material = wrong permeability = wrong coupling or suppression.
SC2-5. A wirewound resistor has several microhenries of series inductance. At HF and VHF, this adds inductive reactance proportional to frequency, destroying the resistor's value as a termination or load.
Checkpoint
Before proceeding: - [ ] You have read Chapter 3 completely - [ ] You can name the critical components from memory - [ ] You understand why non-inductive and correct ferrite materials are required
→ Proceed to Unit 3