๐ The Scroll
"Ancient Reference Knowledge, Preserved Forever"
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๐ Sensei's Reference Scroll Index
These scrolls contain the accumulated knowledge of SensorSensei over many moons.
Print them out and keep them near your workbench!
| ๐ Scroll Number |
๐ Reference Topic |
๐
Date Added |
| Scroll #001 |
Sensor Pinout Reference Chart |
04/01/2026 |
| Scroll #002 |
Analog-to-Digital Converter (ADC) Guide |
04/03/2026 |
| Scroll #003 |
I2C Address Reference Table |
04/05/2026 |
| Scroll #004 |
Resistor Color Code Reference |
04/08/2026 |
| Scroll #005 |
Common Sensor Voltage Requirements |
04/10/2026 |
| Scroll #006 |
Arduino Pin Mapping (All Boards) |
04/15/2026 |
* . * . * . * . * . * . * . *
๐ Scroll #001: Sensor Pinout Reference
"A wrong pin connection burns both sensor and programmer." โ SensorSensei
๐ก๏ธ LM35 Temperature Sensor Pinout
| Pin |
Name |
Description |
Connection |
| 1 |
Vout |
Analog voltage output (10mV/ยฐC) |
Arduino A0 |
| 2 |
Vcc |
Power supply (4V-30V) |
Arduino 5V |
| 3 |
GND |
Ground |
Arduino GND |
๐ง DHT11 Humidity Sensor Pinout
| Pin |
Name |
Description |
Connection |
| 1 |
Vcc |
Power (3.5V-5.5V) |
Arduino 5V |
| 2 |
Data |
Single-wire digital output |
Arduino D2 (+ 10K pull-up) |
| 3 |
NC |
No connection |
Leave unconnected! |
| 4 |
GND |
Ground |
Arduino GND |
๐ณ MPU6050 Accelerometer/Gyro Pinout
| Pin |
Name |
Description |
Connection |
| 1 |
Vcc |
Power (3.3V ONLY!) |
Arduino 3.3V |
| 2 |
GND |
Ground |
Arduino GND |
| 3 |
SCL |
I2C Clock |
Arduino A5 (UNO) |
| 4 |
SDA |
I2C Data |
Arduino A4 (UNO) |
| 5 |
XDA |
Extended I2C (unused) |
Leave unconnected |
| 6 |
XCL |
Extended I2C (unused) |
Leave unconnected |
| 7 |
AUX_CL |
Sensor auxiliary clock |
Leave unconnected |
| 8 |
AUX_DA |
Sensor auxiliary data |
Leave unconnected |
| 9 |
INT |
Interrupt pin |
Arduino D2 (optional) |
+ ~ + ~ + ~ + ~ + ~ + ~ + ~ +
๐ Scroll #002: ADC (Analog-to-Digital) Guide
๐ What is ADC?
ADC stands for Analog-to-Digital Converter.
It is the bridge between the analog world (real-world signals) and the digital world (your microcontroller).
๐ Arduino ADC Reference
| Specification |
Value |
| Resolution |
10 bits (1024 levels) |
| Reference Voltage |
5V (default) or 3.3V (3.3V boards) |
| Formula |
Voltage = (readValue / 1024) ร Vref |
| Sample Rate |
~15 kHz maximum |
๐งฎ Sensei's ADC Conversion Table (5V Reference)
| Analog Value (0-1023) |
Voltage |
What It Means |
| 0 | 0.00V | Ground / Nothing detected |
| 205 | 1.00V | Low signal |
| 410 | 2.00V | Medium-low signal |
| 512 | 2.50V | Half reference voltage |
| 614 | 3.00V | Medium-high signal |
| 819 | 4.00V | Strong signal |
| 1023 | 5.00V | Maximum (full reference) |
"Remember, grasshopper: 1024 levels of truth. Each step of 4.88mV at 5V reference.
Know your numbers, and the sensors will reveal their secrets." โ SensorSensei
* . * . * . * . * . * . * . *
๐ Scroll #003: Common I2C Addresses
Save this scroll! Knowing I2C addresses saves hours of debugging!
| Sensor |
I2C Address (Hex) |
Notes |
| MPU6050 | 0x68 | May be 0x69 if AD0 pulled high |
| BMP280 / BMP180 | 0x76 | May be 0x77 if SDO pulled high |
| SHT31 | 0x44 | Default address |
| HTU21D | 0x40 | Fixed address |
| BH1750 | 0x23 | Default (light sensor) |
| TCS34725 | 0x29 | RGB color sensor |
| LCD I2C Backpack (1602) | 0x27 | May be 0x3F on some modules |
| PCF8591 (ADC/DAC) | 0x48-0x4F | Depends on A0/A1 pins |
| DS3231 (RTC) | 0x68 | Same as MPU6050! Not at same time! |
| MLX90614 (IR Temp) | 0x5A | Contactless temperature |
๐ SENSEI'S TIP: Use an I2C scanner sketch to discover addresses on your bus!
"The scanner reveals all secrets." โ SensorSensei
+ ~ + ~ + ~ + ~ + ~ + ~ + ~ +
๐ Scroll #004: Resistor Color Code Reference
The ancient art of reading resistors by eye. Master this, and you shall never need a multimeter for basic values!
| Color | Digit | Multiplier | Accuracy |
|---|
| โฌ Black | 0 | ร1 | โ |
| ๐ซ Brown | 1 | ร10 | ยฑ1% |
| ๐ฅ Red | 2 | ร100 | ยฑ2% |
| ๐ง Orange | 3 | ร1K | ยฑ3% |
| ๐จ Yellow | 4 | ร10K | ยฑ4% |
| ๐ฉ Green | 5 | ร100K | ยฑ0.5% |
| ๐ฆ Blue | 6 | ร1M | ยฑ0.25% |
| ๐ช Violet | 7 | ร10M | ยฑ0.1% |
| ๐ช Gray | 8 | โ | ยฑ0.05% |
| โฌ White | 9 | โ | โ |
๐ Common Resistors for Sensors:
- 10Kฮฉ (Brown-Black-Orange) โ Pull-up for DHT, LDR divider
- 220ฮฉ (Red-Red-Brown) โ LED current limiting
- 4.7Kฮฉ (Yellow-Violet-Red) โ I2C pull-up common value
- 1Kฮฉ (Brown-Black-Red) โ Various digital pull-ups
* . * . * . * . * . * . * . *
๐ Scroll #005: Common Sensor Voltage Requirements
โ ๏ธ WRONG VOLTAGE = DEAD SENSOR! READ THIS SCROLL TWICE! โ ๏ธ
| Sensor |
Operating Voltage |
Safe for 5V Logic? |
Safe for 3.3V Logic? |
| LM35 | 4V - 30V | โ
Yes | โ
Yes |
| DHT11 | 3.5V - 5.5V | โ
Yes | โ ๏ธ Marginal |
| DHT22 | 3.3V - 5.5V | โ
Yes | โ
Yes |
| MPU6050 | 2.3V - 3.6V | โ NO! Use level shifter! | โ
Yes |
| BMP280 | 1.7V - 3.6V | โ NO! Use level shifter! | โ
Yes |
| BH1750 | 2.4V - 3.6V | โ NO! Use level shifter! | โ
Yes |
| HC-SR04 | 5V | โ
Yes (5V output) | โ ๏ธ Needs divider! |
| MQ-2 | 5V (heater) / 3.3V (output) | โ
Yes | โ
Yes |
| HC-SR501 (PIR) | 4.5V - 20V | โ
Yes | โ
Yes |
"The MPU6050 that died was my fault, not yours. But remember: 3.3V sensors DO NOT LIKE 5V!"
โ SensorSensei, still haunted by his first burnt MPU6050
๐งโ ๏ธ๐ง
More scrolls being written by the monastery scribes! Check back soon!
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