Circuit diagrams and schematics - Electronic projects

The LM555 timer can achieve a 50 percent duty cycle as shown in the next diagram. The duty cycle adjustment range of the give components values is from 42 to 55 percent. Resistors R1 and R2 were selected first and then resistor R3 was selected to give the best control range based on measurements at [...]

The next section shows how the LM555 timer could be used as a voltage comparator or a wide offset Scmitt Trigger. Applications for which it is not particularly well suited but one that is in wide use with model railroaders. Shown on the schematic is a secondary output that uses the open collector at the [...]

These circuits show methods of changing the operating frequency of astable LM555 timers electronically. Any source that can drive the base of transistor Q1 can control these circuits. The advantage of using this type of frequency control is that the duty cycle of the timer is not affected when the frequency is changed. [...] Read [...]