How Mosquito Racket Works......%....

Hello everyone!! In this section we’ll be seeing different circuits and their applications. Has anyone seen this ?

No it’s not a tennis racket! It’s a mosquito racket. This is what happens in it: it has got an inner grid and an outer grid. These two terminals are from a voltage doubler – where the voltage has been doubled and tripled to such a level that the voltage is in thousands of volts. Now along comes an unassuming mosquito which gets caught in between the terminals. The circuit is completed and a very large voltage is applied to the mosquito which causes it to explode.

To see a quick demo of what we mean click here

There is rechargeable battery in it which stores DC charge when the. This DC is converted to an ACsignal using an inverter and that is given to a voltage multiplier which produces a high voltage. This very high voltage is given to the two terminals of the grids.

As the name suggests this circuit converts AC electrical power from a lower voltage to a higher DC voltage, typically using a network of capacitors and diodes. In principle it’s a rectifier. We can see that from the presence of the diodes.

The input is a sinusoidal AC signal. During the positive half-cycle, diode D0 conducts, D1 is cut off. The capacitor C0 will charge to the peak rectified voltage. During negative half-cycle, the diode D0 is cut off and D1 will be forward biased. Diode D1 is a short and D0 is open. So take it as a loop as shown below.

So at the point marked A the voltage will be the sum of the negative peak (Vm)and the voltage across the capacitor with the sign as shown. This is 2 times Vm Similarly C2 will be charged to 2Vm in negative half-cycle. Since diode D1 is short then, the voltage at A will charge the capacitor C1. The voltages will be as shown:

Vmeter1 will read 2Vm and Vmeter0 will read Vm plus 2Vm which is 3Vm. Thus this can be repeated with consecutive stages. Voltages taken at the top of transformer winding as shown will give odd multiple voltages and voltages taken from the bottom transformer winding will give even voltage multiples. Confused? Okay. Add another stage i.e. capacitor and diode,then think what should happen.

Friends’,analyzing a circuit is not very tough. First know what the inputs are – in thiscase a simple sinusoidal ac signal. That is half the job done. Then see how the behavior is for that particular input. If you can break down the input into further steps it’s much better. Understanding the behavior of the various components will help you further follow up the working. Well I guess it may allsound a bit weird, but we’ll be seeing more of this in the coming weeks with more interesting circuits and electronics fun. Meanwhile why don’t you tryrigging up this circuit and running it?  The capacitors are 1 nF. And an input more than 2V is better as the diode has to be forward-biased.

Let’s look at some places where this circuit is used. Voltage doublers are used in switched mode power supplies. Some power supplies require 120 V as well as 240V. So an SPDT switch will be used to select either of the voltages. Voltage tripplers are used to create high voltages in CRTs, printers and photocopiers. Note that even though very high voltage is to be generated, the individual components need not withstand the entire voltage range.