155 lines
3.7 KiB
Markdown
155 lines
3.7 KiB
Markdown
# Capacitor Symbol Types in KiCad
|
|
|
|
## For This Project: Use **UNPOLARIZED** Symbols
|
|
|
|
All capacitors in this design are **ceramic capacitors**, which are **unpolarized**.
|
|
|
|
---
|
|
|
|
## Capacitor Types in This Design
|
|
|
|
### C1, C2: 10µF Capacitors
|
|
- **Type:** Ceramic (X7R or X5R)
|
|
- **Symbol:** **Unpolarized** (non-polar)
|
|
- **KiCad Symbol:** `Device:C` (standard capacitor symbol)
|
|
- **Package:** 0805
|
|
|
|
### C3, C4, C5-C13: 100nF Capacitors
|
|
- **Type:** Ceramic (X7R)
|
|
- **Symbol:** **Unpolarized** (non-polar)
|
|
- **KiCad Symbol:** `Device:C` (standard capacitor symbol)
|
|
- **Package:** 0805
|
|
|
|
---
|
|
|
|
## Polarized vs Unpolarized Capacitors
|
|
|
|
### Unpolarized Capacitors (Ceramic)
|
|
- **Symbol:** Two parallel lines (no + or - marking)
|
|
- **KiCad Symbol:** `Device:C`
|
|
- **Types:** Ceramic, Film, Mica
|
|
- **Can be connected either way** - no polarity
|
|
- **Used in this project:** All capacitors (C1-C13)
|
|
|
|
### Polarized Capacitors (Electrolytic)
|
|
- **Symbol:** One curved line (negative) and one straight line (positive)
|
|
- **KiCad Symbol:** `Device:CP` (polarized capacitor)
|
|
- **Types:** Aluminum electrolytic, Tantalum
|
|
- **Must be connected correctly** - has + and - terminals
|
|
- **NOT used in this project**
|
|
|
|
---
|
|
|
|
## How to Add Capacitors in KiCad
|
|
|
|
### Step 1: Add Symbol
|
|
1. Press `A` (Add Symbol)
|
|
2. Search for: `Device:C` (unpolarized capacitor)
|
|
3. Place on schematic
|
|
|
|
### Step 2: Set Value
|
|
1. Press `E` (Edit) on the capacitor
|
|
2. Set **Value** field:
|
|
- C1, C2: `10µF` or `10uF`
|
|
- C3-C13: `100nF` or `0.1µF`
|
|
|
|
### Step 3: Set Reference
|
|
- KiCad will auto-assign references (C1, C2, etc.) when you annotate
|
|
|
|
---
|
|
|
|
## Visual Guide
|
|
|
|
### Unpolarized Capacitor Symbol (Use This)
|
|
```
|
|
| |
|
|
| |
|
|
| |
|
|
```
|
|
Two parallel lines - **no polarity marking**
|
|
|
|
### Polarized Capacitor Symbol (Don't Use)
|
|
```
|
|
| |
|
|
| |
|
|
+ |
|
|
```
|
|
One curved line (negative) - **has polarity**
|
|
|
|
---
|
|
|
|
## Why Ceramic Capacitors?
|
|
|
|
**Advantages:**
|
|
- ✅ Unpolarized (no orientation issues)
|
|
- ✅ Small size (0805 package)
|
|
- ✅ Low cost
|
|
- ✅ Good for decoupling and filtering
|
|
- ✅ No leakage current issues
|
|
- ✅ Long lifespan
|
|
|
|
**For 10µF capacitors:**
|
|
- Ceramic capacitors in 0805 package are available up to 22µF
|
|
- X7R or X5R dielectric provides good stability
|
|
- 16V rating is sufficient for 5V input
|
|
|
|
**For 100nF capacitors:**
|
|
- Standard ceramic capacitor value
|
|
- Excellent for high-frequency decoupling
|
|
- Very common and inexpensive
|
|
|
|
---
|
|
|
|
## KiCad Symbol Library
|
|
|
|
**Use this symbol:**
|
|
- **Library:** `Device`
|
|
- **Symbol Name:** `C` (Capacitor)
|
|
- **Footprint:** `Capacitor_SMD:C_0805_2012Metric`
|
|
|
|
**Do NOT use:**
|
|
- `Device:CP` (Polarized Capacitor) - This is for electrolytic capacitors
|
|
|
|
---
|
|
|
|
## Summary
|
|
|
|
| Capacitor | Value | Type | Symbol | KiCad Symbol |
|
|
|-----------|-------|------|--------|--------------|
|
|
| C1, C2 | 10µF | Ceramic | Unpolarized | `Device:C` |
|
|
| C3, C4 | 100nF | Ceramic | Unpolarized | `Device:C` |
|
|
| C5-C13 | 100nF | Ceramic | Unpolarized | `Device:C` |
|
|
|
|
**All capacitors use the same unpolarized symbol: `Device:C`**
|
|
|
|
---
|
|
|
|
## Common Mistakes to Avoid
|
|
|
|
❌ **Don't use:** `Device:CP` (polarized capacitor symbol)
|
|
- This is for electrolytic capacitors
|
|
- Has polarity markings (+ and -)
|
|
- Not needed for ceramic capacitors
|
|
|
|
✅ **Do use:** `Device:C` (unpolarized capacitor symbol)
|
|
- Standard capacitor symbol
|
|
- No polarity markings
|
|
- Correct for all capacitors in this design
|
|
|
|
---
|
|
|
|
## When Would You Use Polarized Capacitors?
|
|
|
|
Polarized capacitors (electrolytic) are typically used for:
|
|
- Large capacitance values (>100µF)
|
|
- Power supply filtering
|
|
- When you need very high capacitance in a small volume
|
|
|
|
**For this project:** Ceramic capacitors are sufficient and preferred because:
|
|
- They're smaller
|
|
- They're cheaper
|
|
- They don't have polarity issues
|
|
- They work well for decoupling and filtering
|
|
|
|
|