Spot the Mistakes - Index
Colin Mitchell
Colin Mitchell
December 15, 2015
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These pages have become a valuable source for learning and understanding electronics.
You will find answers that have never been covered in any text book.
For this reason we have decided to produce an index so you can quickly locate some of the things we have covered.

  • Adjustable Regulator - how NOT to adjust a regulator Never leave the Common pin floating.
  • Adjustable Voltage - more advice on how NOT to adjust the voltage on a 3-terminal regulator
  • Biasing Resistors - notes on Biasing Resistors
  • Car Interior Light
  • Coupling
  • Current - showing the direction of CURRENT-FLOW
  • Current - how to measure current
  • Diode - Measuring a diode
  • Faulty Design - how to design a circuit correctly and see faults in a circuit.
  • Flip Flop using CD4011 IC
  • Hearing Aid - A Hearing Aid circuit with a number of faults.
  • A Joule Thief Circuit - designing a Joule Thief Circuit
  • Key Hole Light - the circuit flattened the batteries in 2 months!
  • [LED Current](/blog/spot-the-mistakes-7#LED Current) - the current through a LED
  • [LED Dice](/blog/spot-the-mistakes-5#LED Dice) - A badly-designed circuit is discussed.
  • LED Flasher - an emitter-follower is not a good idea.
  • [LED Flashers](/blog/spot-the-mistakes-4#LED Flashers) - designing a LED Flasher circuit
  • LEDs in Series -
  • LED Voltage Indicator - resistor values to turn on LEDs in a “staircase.”
  • [Mat Switch](/blog/spot-the-mistakes-5#Mat Switch) - Don’t use a 555 - It wastes 10mA!!
  • Motor Driver
  • Music Chip - the need for a current-limiting resistor
  • Night Light - improving the circuit
  • Oscillator Circuit - how the feedback osc works - it uses a 2-transistor high-gain amplifier.
  • Oscillator Circuit -
  • Oscillator - How NOT to design an oscillator circuit.
  • Power Failure Alarm - see the circuit for the fault.
  • Push Pull - helpful advice on designing a PUSH PULL output.
  • Sawtooth Waveform
  • Sound Meter - faults with a microcontroller circuit
  • Stop Resistor - the important of a Stop Resistor
  • Stress Meter - Learn about unnecessary components in a circuit.
  • Thermal Conduction - a very good article to show how to design tracks on a PC board.
  • Touch Switch - How to design a Touch Switch circuit.
  • Tracking Transmitter - designing a tracking Transmitter circuit
  • Turn ON - designing a Turn ON circuit
  • Voltage Doubler - using a 555 and how to reduce the number of components.
  • Water Detector -
  • Wind Turbine Water Heating -
  • UM 3561 4-Sound IC -
  • 1k Load Resistor - designing a circuit correctly
  • 2 Digit Display - how to drive 7-segment displays
  • 12v Adapter - the need to show component values
  • 56R - a badly designed circuit with a 56R wasting current ALL THE TIME.
  • 500mA - the circuit states 800mA but the transistor will only deliver 100mA.


Colin Mitchell

Colin Mitchell



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