Circuits that create or shape a single pulse or a regular stream of pulses (clock). 


A clock signal is one that transmitts a steady stream of pulses, usually carefully timed and controlled. This is a master control signal typically used in synchronous systems. Many SC logic components can be run synchronously since they have a clock input. However, there is little use for synchronous systems in the vast majority of SC circuits and the clock input is either ignored or often used in an alternative fashion.

A pulse is a single 'blip' in the signal line. A pushbutton creates a pulse - it is only only on for a short time and then turns back off. A pulse can be used in synchronous systems to force all components to update their outputs at the same time. Again, this has little value in most SC circuits.

Shaping a pulse or clock means that certain attributes of the signal are modified by either eliminating, reducing, expanding or transforming them. Most shaping circuits either shorten or extend the on-time of a pulse or clock.

Square Wave is a signal that may run continuously. It regularly switches from off to on and back, etc. The signal is considered 'square' when the off-time is the same as the on-time. When the signal is displayed on a screen, it can be imagined as a tidy row of boxes precisely placed so that exactly one box will fit between each other box.


The circuits that follow are useful in clocking circuits and other pulse based circuitry.

The switches, buttons, LED or light are shown simply to let you know where to connect the inputs and outputs. They are NOT a necessary part of the circuits.


This is a simple circuit for generating a clock stream. It will output a square wave at a fairly well regulated frequency. This frequency can be decreased by adding more delay gates in series with the one included. Check out the delay gate page to understand how delays work in SC electrics.

Survivalcraft 2014-10-13 18-11-53-

This oscillator runs just over 2 Hz or 2 cycles each second. Add delay gates to decrease the frequency. If you need longer and more precise periods, you may want to use an RTC with a 4-bit counter.

Fast clock

A fast oscillator can be made without the delay gate. This will run approximately 10 Hz? (on a fast enough device).

Pulse Shaper

Pulse stretcher
This circuit takes a pulse of varied duration and outputs a pulse of a fixed duration. You can set the pulse length by the number of delay gates in the circuit. As shown, this circuit puts out a pulse approximately 1 second long. The length is independant of whether a switch or button or other signal is used to activate the circuit. It always outputs the pulse when the input goes high.

This can also be used to condition longer pulses before being sent to the pulse doubler. It will turn a steady ON signal into a pulse. You may use only 1 delay gate in that case.

Differentiator or Edge Detector

An edge detector is a circuit that recognizes both the rising and falling edges of a signal and outputs a pulse for each condition. That means that whenever the input signal changes, the circuit pulses the output. So if a switch is used as the input, it will pulse when the lever is turned on and also when it is turned off.

The output pulse is quite short and may even be difficult to see with a light or an LED, but it is long enough to activate any circuits that follow. If you need a longer pulse, feed this into a pulse shaper.

Pulse Multiplier

Pulse multiplier
This circuit will accept a pulse as an input. It will output a pulse when it gets one. It will also output a second pulse some time later (about 5 seconds in this design). This is useful to activate doors and have them close automatically once you have a chance to get inside.

This circuit also has the ability to be a differentiator if the input pulse is longer than the output pulse time. It is meant to be used with a short input pulse. You can use the pulse shaper to condition longer signals before using this circuit.

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