{"id":2743,"date":"2017-01-30T00:00:57","date_gmt":"2017-01-30T08:00:57","guid":{"rendered":"http:\/\/192.168.3.4\/?p=2743"},"modified":"2018-01-09T06:51:28","modified_gmt":"2018-01-09T14:51:28","slug":"2743","status":"publish","type":"post","link":"https:\/\/www.cloudacm.com\/?p=2743","title":{"rendered":"Signals – Digital, Analog, and PWM"},"content":{"rendered":"

In this post I’ll be covering fundamental electronic signals.\u00a0 These will establish a foundation for us to work from as I begin to cover more advanced signaling technology.\u00a0 First, we will cover digital signals.\u00a0 These are the most basic since they are either on or off.\u00a0 Next, we cover RC Time circuits which allow us to use a digital port to read an analog condition.\u00a0 We’ll follow that up with analog signals and how we read them electronically.\u00a0 Next, I’ll cover pulse width modulation (PWM) as a way for us to create analog signals from a digital source.\u00a0 Lastly, we’ll explore conditioning circuits that work with analog signals to bring them into a working headroom for our devices.<\/p>\n

What are signals and what purpose do they serve?\u00a0 Signals are essentially voltage levels and we use them to do a whole host of things like, turn on a light, listen to music, adjust the temperature of a room, and much more.\u00a0 I won’t be going into specifics, but I will be focusing our attention of signals towards those used by devices like the raspberry pi and arduino, along with the sensors that feed them.<\/p>\n

As I mentioned, digital signals are basically voltage levels that are either on or off.\u00a0 Think of them like the light switch in a room.\u00a0 When the digital signal is low, the light in the room is off.\u00a0 When the digital signal is high, the light in the room is on.<\/p>\n

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Devices like the raspberry pi and arduino read the digital state by detecting a voltage level above or below a given threshold.\u00a0 By and large, all digital devices use logic levels<\/a> to determine the state of an input.\u00a0 They also use these logic levels when creating a digital output signal.\u00a0 The threshold voltages allow for clean operation in situations where noise, loss, and other factors would degrade the digital signal.\u00a0 The difference between the high state threshold and low state threshold is referred to as the gap voltage.\u00a0 The larger the gap, the more resilient to noise and loss the logic level is.<\/p>\n

One key benefit to using set logic levels is the accurate detection when a threshold is crossed.\u00a0 This is central to using digital inputs as a way to measure analog signals.\u00a0 To do that we use the RC time circuit<\/a>.<\/p>\n

First, lets cover what an analog signal is.\u00a0 Let’s use the room light as example again.\u00a0 Instead of the light being turned on or off with a switch, we now use a dimmer to adjust the brightness of the light.\u00a0 The varying levels of voltage is what makes it an analog signal.<\/p>\n

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Now back to detecting the analog signal on a digital input.\u00a0 As mentioned, the RC time circuit is used to make this possible.\u00a0 The RC time circuit consists of a variable resistor and a capacitor.\u00a0 The value of the resistor is changed by the analog input.\u00a0 When this occurs, the time it takes for the capacitor to discharge across the resistor changes.\u00a0 Here is the theory behind it.<\/p>\n