4) has two pins in between the resistor and capacitor that determine the time constant. In the previous section we discussed the pins. The first thing to consider before writing down equations is to understand how the 555 timer determines when to reset. We are going to get into some slightly advanced mathematics in this section to explain how we arrive at the following equation for how long the pulse will be.
Capacitor as timer circuit how to#
We will discuss how to find this charging time in the next section. However, the time is determined by how long it takes to charge a capacitor to a certain voltage. We have been saying that the monostable circuit outputs for a set amount of time. The main takeaway from both of these figures is that monostable circuit is triggered by the first spike and bounce spikes are ignored this happens because a monostable circuit outputs HIGH for a set amount of time, and thus will ignore any bounces that occur during that time frame. Figure 2 is the scoped monostable circuit using a 555 timer, showing the same action. It is this property that will make it possible to debounce the button, since once triggered, it can't be re-triggered until after it resets for the set time.įigure 1 below shows the basic behavior of the output of a monostable circuit with a bouncing input. USB Scopes, Analyzers and Signal GeneratorsĪ monostable circuit is a circuit where only one of the states is stable (doesn't change without trigger), and the other state (unstable state) changes back to the stable state after a set time.
0 kommentar(er)
