Make Electronics-Ex 17b

555 TIMER : ASTABLE MODE Variation 1: In experiment 17a, we noted that the charging and discharging time for the 22 nF capacitor were different. When charging it had to go through 2x10k ohms resistors + the pot, when discharging to Pin 7 it had to go through only the pot and 1x10k ohms resistor (on the way to the DIS Pin 7). Here we remove the pot and use a diode to make sure the charging and discharging times are the same. Here I changed the resistors to 2x 100K in order to lengthen the pulse cycle so that EveryCircuit could find a solution. EXPLANATION: When the 22 nF cap charges from the + side of the circuit, the 2nd 100K resistors is bypassed as the current goes though the diode instead. When the cap discharges, the diode blocks the flow of electricity the other way and there is only 1x100K resistor in the way between the 22 nF cap and Pin 7 (DIS). So now, whether the cap charges or discharges it faces the same amount of resistance both ways. Therefore, the ON and OFF cycles are now of equal duration compared to experiment 17a.

published 7 years ago