Custom Firmware, Electronics Design, and PCB Layout

Circuit Building Blocks

The following are links to useful circuits, which can be used to build larger designs.

• 49MHz Toy AM Transmitter - Simple 2 transistor AM transmitter. 
• Gyrator - Telephone DC holding circuit.
• DAA - Data access arrangement circuit.
• Energy Harvester Circuit - Harvests energy from a small source such as a piezo buzzer, and boosts the voltage to 3.3V 
• Flyback SMPS - Uses an off the shelf flyback transformer to create a 40V boosting power supply, with a non-dissipative snubber.
• High Side Current Monitor - Monitor a load with a high side sensing resistor.
• HV MOSFET Driver - Drive a complementary pair of MOSFETs with a high voltage supply 
• Inverse Voltage Control - Create a voltage inversely proportional to a variable resistor. 
• Joule Thief - Drive LEDs with 1.5V using a transformer based oscillator. 
• Latching Momentary Switch - Turn any momentary switch into a latching switch with just a few components. 
• LED Indictor for Relay - Two LEDs show the NO/NC status of a relay. 
• Non-Inverting Op-Amp Level Shifter - Converts a positive and negative signal into a range suitable for a single supply ADC.
• Pulse Circuits -  Creating, delaying or stretching pulses is a common electrical engineering task.
  
• Saw Transmitter - Simple 433.92MHz transmitter often used in key fobs.
• SDI-12 Bus Interface - Hardware interface for connecting a microcontroller with a 1200 baud UART to an SDI-12 bus.
• Selectable Voltage Source - Allow a microcontroller to select between two different voltage levels from a standard voltage linear voltage regulator.
• Short-Circuit Protection Circuit - Protect the output of a power amp or power supply from shorts across the output leads. 
• Level Translators: 3V and 5V - Interface 3V and 5V logic signals. 
• Transformerless Power Supplies - Power circuits from wall current, without the use of a transformer. 
• Transistor AC OpAmp - A 3 transistor AC OpAmp Circuit.
• Transistor Schmitt Trigger - Schmitt trigger circuit uses two transistors.
• Variable PIN Diode Based RF Attenuator - A great RF Volume Control
• Variable Zener - Voltage programmable zener diode
• Voltage Controlled Current Source - Current Servo - Create a current proportional to a control voltage.
• Voltage Controlled Voltage Source- Create a voltage output proportional to a control voltage. 
• Voltage Controlled Voltage Source (Inverse)- Create a voltage output proportional to a negative control voltage.