However, if you check the specs of a voltage regulator onboard your Arduino (it’s a variation of a 1117 5v regulator) you’ll see that it is perfectly capable of dealing with 12 volts. Considering that a LED strip power supply usually provides a bit more than nominal 12 volts (something like 12.3 in fact), you may be tempted to avoid connecting it to Arduino. Most Arduinos have a Vin pin that can be connected to bigger voltages, with 9 volts recommended and 12 volts a safe maximum that, according to some, should be generally avoided. LED strip is usually run off 12 volts, Arduino works on 5 volts. *** All circuits were done in the new MultiSim BLUE from Mouser and NI.Before we start connecting the Arduino to a LED strip, let’s deal with the power source. We will also discuss button debouncing techniques to combat this problem in a future blog post as well.ĭo you have troubleshooting horror stories you want to share? Let us know if floating pins have ever caused you design problems in the comments down below. That is when a microcontroller registers multiple button presses even if the user only pushes the button once due to the mechanical oscillation of the button. We will discuss I2C and open drain circuits further in a future blog post.Īnother issue with reading button presses is called “bounce”. There are other applications such as analog comparators or communication protocols such as I2C that are “open drain” based and thus require a pull-up resistor to raise the voltage on the communications lines. Both will work, you just need to remember how to handle the button press in the firmware. In our button example, use of a pull-up versus a pull-down resistor is rather subjective. This is referred to as “active high” logic. ![]() Alternatively with a pull-down resistor, the I/O pin will normally see a logic low and when the button is pressed it will see a logic high. This is sometimes referred to as “active low” logic. ![]() Using a pull-up resistor the I/O pin will normally see a logic high and when the button is pressed it will see a low. So our solution, as shown in Figure 3, is to insert a pull-up resistor between Vcc and the I/O pin or a pull-down resistor between ground and the I/O. Or at the very least cause power supply voltage to drop to ground potential resulting in a non-functioning device. The short circuit could generate enough heat to damage your circuit. The problem with simply connecting the input to Vcc occurs when you press the button and create a short circuit between Vcc and GND. You might be tempted to solve the problem with a solution seen in Figure 2. Such sources include thermal noise and electromagnetic interference (EMI) since the leads of the chip act like tiny antennas when they are floating. By not being connect to a source, Vcc, or GND, the I/O pin is susceptible to electrical noise that makes the I/O randomly fluctuate between low and high. The microcontroller may register a low, but it might just as well register a high. ![]() But this is not the case because the gate is not connected to ground rather, it is floating. ![]() Now, what happens when the button is released? If you were like me you would assume the microcontroller, now that it is no longer connected to Vcc, would register a logic low. When the momentary button is pressed it connects the I/O pin to Vcc and the microcontroller would register the input as a high. To best explain a floating input and how it can negatively affect your project consider the circuit in Figure 1: One of the most basic of the faults is the infamous “floating pin” or “floating input” that can affect the I/O pins of digital integrated circuits. Many times these faults are fixed with a very simple tweak to the circuit design or component selection. I highlighted the importance of troubleshooting in this earlier blog post regarding my work on the automated energy harvester. When you are just starting off in electronics, there are many design pitfalls that can lead to hours of frustrating troubleshooting.
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