{const container =document.getElementById('kc-proto-6');if (container &&typeof InlineKnowledgeCheck !=='undefined') { container.innerHTML=''; container.appendChild(InlineKnowledgeCheck.create({question:"You're selecting a temperature sensor for an outdoor weather station. Requirements: +/-0.3C accuracy, -40C to +85C range, waterproof, and I2C interface. Which sensor is MOST appropriate?",options: [ {text:"DHT22 - popular, affordable, includes humidity",correct:false,feedback:"DHT22 has +/-0.5C accuracy (not meeting requirement), uses proprietary one-wire protocol (not I2C), and the exposed sensor element is not waterproof without additional encapsulation."}, {text:"SHT31-DIS - high accuracy, I2C, available in waterproof housing",correct:true,feedback:"Correct! SHT31-DIS offers +/-0.2C accuracy (exceeds requirement), I2C interface, -40C to +125C range, and is available in waterproof probe housings (IP67). It's the professional choice for outdoor monitoring."}, {text:"LM35 - analog output for simple interfacing",correct:false,feedback:"LM35 has +/-0.5C accuracy and outputs analog voltage (not I2C). While it has good temperature range, analog signals are susceptible to noise over long cable runs in outdoor installations."}, {text:"DS18B20 - one-wire protocol allows long cable runs",correct:false,feedback:"DS18B20 uses one-wire protocol (not I2C as required) and has +/-0.5C accuracy. While waterproof versions exist and it handles long cables well, it doesn't meet the accuracy or interface requirements."} ],difficulty:"medium",topic:"prototyping" })); }}
1528.3 Actuators
1528.3.1 Motion Actuators
Type
Examples
Driver
Use Cases
Servo Motor
SG90, MG996R
Direct PWM
Precise angle control
DC Motor
Various
L298N, TB6612
Continuous rotation
Stepper Motor
28BYJ-48, NEMA17
DRV8825
Precise positioning
1528.3.2 Switching Actuators
Relays: Electromechanical (5V/12V coil) or solid-state for high-current loads
Transistors: BJT (2N2222) or MOSFET (IRF520) for smaller loads
{const container =document.getElementById('kc-proto-7');if (container &&typeof InlineKnowledgeCheck !=='undefined') { container.innerHTML=''; container.appendChild(InlineKnowledgeCheck.create({question:"Your battery-powered sensor needs to convert 12V from a solar panel to 3.3V for the MCU. The sensor draws 50mA average but 300mA peaks during transmission. Battery life is critical. Which power solution is BEST?",options: [ {text:"LM7805 linear regulator - simple and reliable",correct:false,feedback:"LM7805 outputs 5V (not 3.3V) and would waste (12V-5V) x 0.05A = 0.35W as heat. Linear regulators are inefficient for large voltage drops, reducing battery life significantly."}, {text:"AMS1117-3.3 LDO - low dropout voltage for efficiency",correct:false,feedback:"While AMS1117-3.3 outputs 3.3V, it's still a linear regulator. Efficiency = 3.3V/12V = 27.5%. Most energy would be wasted as heat, poor for battery applications."}, {text:"LM2596 switching buck converter - high efficiency for large voltage drops",correct:true,feedback:"Correct! Switching buck converters achieve 85-95% efficiency even with large input-output voltage differences. LM2596 handles up to 3A output, easily managing 300mA peaks. Much better battery life than linear regulators."}, {text:"Voltage divider with resistors - simplest and cheapest solution",correct:false,feedback:"Voltage dividers cannot provide current - they're only for signal level shifting. At 50mA load, a divider would need massive resistors dissipating watts of heat and the output voltage would collapse."} ],difficulty:"medium",topic:"prototyping" })); }}
1528.5.4 Logic Level Conversion
3.3V to 5V Conversion: - Bi-directional level shifters: TXS0108E, BSS138-based modules - Voltage dividers: Resistive (5V to 3.3V only, not bidirectional) - MOSFET logic level shifters: Low-cost, reliable
WarningCritical: Never Connect 5V to 3.3V Directly
Connecting a 5V output directly to a 3.3V input can damage the 3.3V device. ESP32, Raspberry Pi, and most modern MCUs use 3.3V logic and can be damaged by 5V signals. Always use level shifters or voltage dividers.
1528.6 Prototyping Tools
1528.6.1 Essential Equipment
Tool
Purpose
Recommended
Soldering Iron
Permanent connections
Temperature-controlled, 60W+
Multimeter
Measure V/I/R, continuity
Auto-ranging, True RMS
Power Supply
Provide power during testing
Adjustable 0-30V, current limiting
Oscilloscope
Visualize signals
USB scope or benchtop 50MHz+
Logic Analyzer
Debug digital protocols
8+ channels, I2C/SPI decode
1528.6.2 Additional Useful Tools
Wire strippers and cutters - prepare wires for connections
Helping hands - hold boards during soldering
Heat gun - SMD rework, heat shrink tubing
3D printer - custom enclosures and mounts
ESD protection - anti-static mat and wrist strap
1528.6.3 PCB Prototyping Options
Method
Cost
Time
Best For
Breadboard
$5-15
Minutes
Initial testing
Perfboard
$1-3
Hours
Semi-permanent
Fab service (JLCPCB)
$2-10
1-2 weeks
Production-intent
CNC mill
$200+
Hours
Rapid custom PCBs
1528.7 Whatβs Next
Continue to PCB Design and Fabrication to learn about designing and manufacturing custom printed circuit boards for production-ready prototypes.