KrakenKodersLights/VOLTAGE_DIVIDER_ALTERNATIVES.md

# Voltage Divider Alternatives - Using What You Have

## Solution 1: Using Only 2.2kΩ Resistors (RECOMMENDED)

### Option A: Two 2.2kΩ in Series for Bottom Resistor
This creates a 2.2kΩ top and 4.4kΩ bottom divider.

```
PWM (5V) ────[2.2kΩ]────┬──── To D1 Mini D2 (3.33V)
                         │
                    [2.2kΩ]
                         │
                    [2.2kΩ]
                         │
                       GND
```

**Output Voltage:** 5V × (4.4kΩ ÷ 6.6kΩ) = **3.33V** ✓ SAFE!

**How to Build:**
1. Solder white wire to first 2.2kΩ resistor
2. Connect other end to junction point
3. Solder TWO 2.2kΩ resistors in series from junction to ground
4. Take output from junction to D1 Mini D2

### Option B: Equal Divider (Simplest)
Uses just two 2.2kΩ resistors for a 50/50 divider.

```
PWM (5V) ────[2.2kΩ]────┬──── To D1 Mini D2 (2.5V)
                         │
                    [2.2kΩ]
                         │
                       GND
```

**Output Voltage:** 5V × (2.2kΩ ÷ 4.4kΩ) = **2.5V** ✓ SAFE!

**Pros:** 
- Simplest to build
- Only 2 resistors needed
- Still safe for D1 Mini

**Cons:**
- Lower voltage might miss some PWM pulses in noisy environments
- But should work fine in most cases

## Solution 2: Common Resistor Combinations

### If You Have These Resistors:

| Top Resistor | Bottom Resistor | Output | Safe? | Notes |
|--------------|-----------------|--------|-------|-------|
| 2.2kΩ | 4.7kΩ | 3.4V | ✓ Yes | Very common resistor |
| 2.2kΩ | 2.7kΩ | 2.75V | ✓ Yes | Close to ideal |
| 2.2kΩ | 3.9kΩ | 3.2V | ✓ Yes | Good alternative |
| 2.2kΩ | 2.2kΩ | 2.5V | ✓ Yes | Equal divider |
| 1kΩ | 2.2kΩ | 3.4V | ✓ Yes | If you have 1k |
| 1kΩ | 1.5kΩ | 3.0V | ✓ Yes | Perfect output |

## Solution 3: No Resistors? Emergency Options

### Use LEDs as Voltage Droppers (NOT RECOMMENDED)
```
PWM (5V) ──── Red LED ──── To D1 Mini D2 (~3.3V)
```
- Red LED drops ~1.7V
- Output: 5V - 1.7V = 3.3V
- **WARNING:** Not reliable, use only for testing!

### Use Diodes (Better than LEDs)
```
PWM (5V) ──── 1N4148 ──── 1N4148 ──── To D1 Mini D2 (~3.6V)
```
- Each silicon diode drops ~0.7V
- Two diodes: 5V - 1.4V = 3.6V
- **Borderline safe** - D1 Mini can usually handle 3.6V

## Solution 4: Find Resistors in Old Electronics

### Where to Look:
1. **Old computer power supplies** - Full of resistors
2. **Broken LED bulbs** - Often have 1kΩ-10kΩ resistors
3. **Old TVs/Monitors** - Tons of resistors
4. **Broken phone chargers** - Usually have some resistors
5. **Old Arduino/electronics kits** - Check breadboard projects

### How to Identify Values:
Use online resistor color code calculator or multimeter

## Solution 5: Make Your Own 3kΩ-ish Resistor

### Parallel/Series Combinations:
To get ~3kΩ from 2.2kΩ resistors:

**Option 1:** 2.2kΩ + 1kΩ in series = 3.2kΩ
**Option 2:** 2.2kΩ + 680Ω in series = 2.88kΩ
**Option 3:** 2.2kΩ + 820Ω in series = 3.02kΩ

## Quick Test Your Divider

### With Multimeter:
1. Connect to 5V source (USB charger works)
2. Measure voltage at junction
3. Should read between 2.5V - 3.3V

### Test Code for D1 Mini:
```cpp
void setup() {
  Serial.begin(115200);
  pinMode(D2, INPUT);
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  // Read digital state
  int state = digitalRead(D2);
  digitalWrite(LED_BUILTIN, !state);
  
  // Try to read PWM
  unsigned long pulse = pulseIn(D2, HIGH, 50000);
  if (pulse > 0) {
    Serial.print("SUCCESS! PWM: ");
    Serial.println(pulse);
  } else {
    Serial.println("Waiting for PWM...");
  }
  delay(100);
}
```

## Recommended Build with 2.2kΩ Only

### Materials:
- 3× 2.2kΩ resistors
- Servo cable
- Small piece of wire

### Steps:
1. **Cut and strip servo cable** (keep female end)
2. **Build the divider:**
   - White wire → 2.2kΩ → Junction
   - Junction → 2.2kΩ → 2.2kΩ → Black wire
   - Junction → Wire to D1 Mini D2
3. **Connect power:**
   - Red wire → D1 Mini 5V
   - Black wire → D1 Mini GND
4. **Test it!**

### Visual Build:
```
  [Servo Cable]
       |
   R━━━B━━━W━━━━━[2.2k]━━━━●━━━━> To D1 Mini D2
   |   |                    |
   |   |              [2.2k]━━[2.2k]
   |   |                    |
   |   └────────────────────┘
   |
   └──> To D1 Mini 5V
```

## Why These Work

The D1 Mini GPIO pins are rated for 3.3V but can tolerate up to 3.6V briefly. Any voltage between 2.5V and 3.3V will work reliably:

- **2.5V** - Minimum reliable HIGH signal
- **3.0V** - Ideal target
- **3.3V** - Perfect match
- **3.6V** - Maximum safe limit
- **5.0V** - WILL DAMAGE THE D1 MINI!

## Final Tips

1. **When in doubt, measure!** Use a multimeter if you have one
2. **2.5V is better than 5V** - Lower voltage is safe, too high will kill the D1 Mini
3. **Test with LED first** - The onboard LED should blink when receiving PWM
4. **Use what you have** - Many combinations work, just stay under 3.6V

## Shopping List (if you need to buy)

Minimum parts from Amazon/eBay:
- **Resistor kit** (~$5-10) - Includes hundreds of values
- **2.7kΩ resistor** (5 pack ~$1) - Makes perfect 3V with 2.2kΩ
- **3kΩ resistor** (5 pack ~$1) - Close enough to 3.3kΩ
- **4.7kΩ resistor** (5 pack ~$1) - Common value, works great

Any of these will work perfectly with your 2.2kΩ resistor!