What's with all these squares with funny numbers?

As we already are in an age where most analogic components are easily replaceable with their digital counterparts, we begin to have new devices that can accomplish the same effects as old timers and pulse generators, being less than half the size of them and having twice their efficiency. In this post we'll analyze some of the most common configurations for combinational circuits, being these the Astables, Latches and One Shots.

In order to understand better what we're talking about, we'll interpret signals and their two binary states, HIGH, that represents a logical 1 and LOW, representing the logical 0, and these two states can be changed through the operation of these elements, not to mention that some need to be feeded previously with HIGH/LOW waves in order to give a value at Its output. Without more to say in this short introduction, It's time we proceed to mention them.

One Shots

What characterizes One shots is the fact that they have one stable state (Being this HIGH or LOW) and one almost-stable state for Its output. the almost-stable state receives this name because the one shot will present "resistance" to this conmutation and will quickly come back to the stable state. the almost stable output will be reached by conmuting the device via an input (That depending on the designer indications will be required to be HIGH or LOW) that will cause the output to change for a determined period of time before going back to the stable state. Also, we can separate One shots in two categories, retriggerable and non-retiggerable. For retriggerable, we mean that If we activate the input more than once when the almost-stable state hasn't finished Its period, the conmutation will reset Itself and as a consequence, the output in the almost stable state will be longer in reference to the time It lasts. For Non-Retriggerable One shots, activating the input more than once when the almost stable state of the output hasn't finished won't cause an effect. If we desire to change the time the almost stable state will last, we only have to change the arrangement of resistors and capacitors in the configuration of the device.

Latches

What differentiates these from one shots is the fact that they have not one, though two stable states, meaning that they can easily change from LOW to HIGH and keep the output at the latter state for the desired time, happening the same If we wish to change from HIGH to LOW. Another distinction between Latches and one shots is their configuration, which will vary with the device used, usually being easier, as Is the case of the 555, in which the threshold and discharge pins are not connected.

Astables or Timers:

The most common of the three, these are used for generating signals by themselves and executing events that change quickly depending on the period they have. These kind of devices don't need inputs to make their function, causing an output that is constantly varying between HIGH and LOW states. the time that the output can last in every state can be controlled by changing the values in the resistors and capacitors present in the configuration of elements of the astable. Timers can be used for alarms, stoplight circuits and all kind of processing operations, hence Its popularity.

As always, we hope that the presentation of these combinational circuits can be of use to you and your future projects, discovering powerful tools for generating signals with different characteristics and lengths depending on the arrangement these have.