NTU-BEM-Lab Homework-A PCB

Todoist

• Replace Power Connector
• Replace all SMT to 0603
• Digital Vcc Decoupling Capacitor
• Buck Converter LM2576 LM2596 LM1117
• Analog Avcc Decoupling Capacitor
• Light Sensor
• Add PhotoCell
• Add Border on PCB
• Change DHT22 to Header
• Add Screw Hole
• Add Test LED

Componenet

• ATmega328P

  • Datasheet

• XBee

  • Datasheet

• DS18B20

  • Datasheet
  • 1-Wire Hub

• DHT22

  • Datasheet

• Common Light Sensors

  • VT90N1 (Light Dependent Resistor)
    • Datasheet
  • TSL235R
    • Datasheet
  • PDV-P8103
    • Datasheet

• Power Supply

  • AMS1117-3.3 over-heating and blow up way below max current
  • 5V Voltage Regulator, LM7805 vs LM2940 vs LM1117 vs AMS1117
  • LM2576
    • Datasheet
    • ELECTRICAL CHARACTERISTICS LM2576-3.3 - 6V ≤ VIN ≤ 40V, 0.5A ≤ ILOAD ≤ 3A
  • LM2596
    • Datasheet
    • Diode is too big (1N5820) (Can use 2N4001 instead of)
    • Overkill
    • 4.75 V ≤ VIN ≤ 40 V, 0.2 A ≤ ILOAD ≤ 3 A
    • 
  • AMS1117
    • Datasheet
    • Out of Stock
  • LM1117
    • Datasheet

Reference

Libraries

• Celestial Altium Library
• SamacSys

Component Considerations

ATmega328P

• Electrical Engineering - What is the minimal set of parts for a circut with this AVR microcontroller?

• AVR® Microcontroller Hardware Design Considerations

  • 2.1 Ditital Supply
    • Put decoupling capacitors near IC
    • For devices with multiple pairs of power and ground pins, it is essential that there is a decoupling capacitor for every pair of pins.
  • 2.2 Analog Supply
    • Avcc ensures the analog circuits are less prone to the digital noise
    • AREF must also be decoupled. The typical value is 100 nF
    • If a separate AGND is present, the ground should be separated from digital ground. (analog & digital grounds are connected only at power supply GND)
  • 3 Connection of RESET Pin on AVR Devices
    • The recommended pull-up resistor value is 4.7 kΩ (For DebugWIRE to function properly, the pull-up must not be less than 10 kΩ)
    • Using an extra capacitor is an additional protection. (cannot be used when DebugWIRE or PDI is used)
    • Recommend add an ESD protection diode (cannot work with HVPP). Alternatively, a Zener diode can be used to limit the Reset voltage relative to GND (highly recommended in noisy environments).
  • 3.1 External RESET Switch
    • It is important to add a series resistance (330R)
  • 4.1 SPI Programming Interface
    • A few ISP programmers are powered by the target power supply. In this way they easily adapt to the correct voltage level of the target board.
    • Other ISP programmers, such as STK600, can alternatively power the target board via the VTG line. In such a case, it is important that the power supply on the target is not switched on.

• Crystal Oscaillator 16MHz

  • Table 8.3 - 12-22 pF

• debugWIRE

• Serial Interface

Others Considerations

SMD / SMT

• Difference between 1206, 0805 and 0603 SMD resistor

  • If you need to hand solder them, I suggest not going too small,e specially if you do not have any experience. 0603 should be fine for almost everyone, 0805 even more so, 1206 is a huge beast you can solder with your hands tied and your eyes closed.

• 0603(0.06 inch * 0.03 inch) == 1608 (1.6 mm * 0.8 mm)

Trace Rules

• PICKING THE RIGHT TRACE WIDTH FOR YOUR NEXT PCB DESIGN