Free electronic circuit design and schematic diagram
This charger circuit is suitable for lead-acid battery, including flooded, gel, and AGM types. The automatic term means that this charger will stop charging automatically when the battery voltage reach a certain pint, indicating that the battery has been fully charged, and charging will be restarted if the battery voltage falls below that threshold. A LED indicator is provided to […]
Read more
This audio frequency meter uses 555 IC as a monostable multivibrator (one-shoot trigger). A monostable multivibrator can act as a frequency-to-voltage converter because it produce a fixed pulse width, with the repetition rate/density is proportional to the triggering input frequency. Here is the circuit’s schematic diagram: For resistor R1, because it set the measurement range, it’s better to use a […]
Read more
The circuit’s schematic diagram shown in the figure below is a flicker noise generator, an implementation of flicker noise analog modeling presented in NBS technical note #604, “Efficient Numerical and Analog Modeling of Flicker Noise Processes” by J.A. Barnes and Stephen Jarvis, Jr. With the component values shown the schematic diagram, the circuit will give a 1/f noise slope from […]
Read more
Voltage-Current curve tracer is very important tools for components ant circuits troubleshooting. This circuit need an oscilloscope with X-Y inputs to display the curve. This circuit provide adjustment for both peak-to-peak voltage and the current limiter. The peak-to-peak voltage selected using different voltage taps of the transformer, and the current limiter is selected by different series resistor. An optional diode […]
Read more
Zero crossing detector is used to convert sine wave or other signal into square-wave, the output should be low if the input is negative and high if the input if positive. Many zero crossing detector use split supply (symmetric supply), but this zero crossing detector circuit only need a single supply, thus suitable for battery-operated circuits. Here is the schematic […]
Read more
Using a single supply quad comparator LM339, LM239, LM2901, LM2901V, NCV2901, or MC3302, we can build a square-wave oscillator with simple circuit and formula. Here is the schematic diagram: This circuit is suitable if you need many square-wave oscillators in one circuit, since the quad packaged comparator provide four comparators in one single integrated chip. [circuit’s schematic diagram source: Motorola […]
Read more
This circuit has similar function with inverting comparator with hysteresis, but the output is not inverted. The output will be high if the input is higher than the upper threshold point, and the output will be low if the input is below the lower threshold point. Here is the circuit’s schematic diagram: What will happen if the input is between […]
Read more