Voltage doubler is the circuit where we get the twice of the input voltage, like if we supply 5v voltage, we will get 10 volt at the output. Generally transformers are there to step-up or step-down the voltage, but sometimes transformers are not feasible because of their size and cost. So here is the quick, easy and practical solution to double the voltage, using 555 timer IC.

The integrator does just what the name implies. It integrates - in the calculus sense - the input signal to produce the output signal. There is a scaling factor and a minus sign again, but that's pretty much what happens.

As per the reader’s request, here is the making of the IR Sensor Module. An IR Sensor module is a sensor that transmits and receives infra-red rays when a surface or object is detected. It is a multipurpose sensor, which can be used in line following robot, obstacle avoiding robot, edge avoiding robot, etc.

This circuit creates a voltage inversely proportional to a variable resistance.

The Schmitt-trigger is a circuit which creates hystereses and which is useful in digitizing an analog signal into a digital signal of either high or low. The hystereses makes inputs more immune to noise. The input must surpass a low threshold voltage before the output goes low, and likewise the input must exceed a high level threshold before the output goes high.