If not then rotate the varistor clockwise or anticlockwise and then you will get your result( since if the varistor was set initially at a value such that the o/p frequency is Khz range then you cannot see the led blinking). If it is all right the LED should blink for the on time period. You can use a multimeter or LED to test the output stage. Now following the above circuit, build this on breadboard. The capacitor at pin 5 is to reduce noise. 1N4007 or anything else) parallel to R2 or Rb with the N side connected to the positive terminal of C. Now the on time and off time can be calculated by the formula given in the picture so for Ra/R1 much less than Rb/R2, you can take it as a square wave.So as an optional you can replace Ra/R1=1K by 1K varistor.Or best for getting a nice clean square wave( if necessary) then add a PN diode(eg. You can use the formula given in the picture for finding that frequency. So by attaching this value of varistor we can get frequency ranging from 0.721Hz-1.443KHz at the output. So I have attached a variable resistance like 1MEG here. As always you can find more info over the net.Now we can change the resistance R2 and can change the frequency. The duty cycle of this wave cannot be less than or equal to 50%. The 555 timer is in astable mode now.At this mode it can generate rectangular/square wave output.
0 Comments
Leave a Reply. |