When you connect capacitors in parallel, you connect them alongside each other. And you can think of them as one capacitor with a higher value. You’ll find that value by adding the values of each capacitor.
For example, if you connect three 1000 µF in parallel, the combined capacitance becomes 3000 µF. This can be useful for getting a specific capacitor value that you don’t currently have in your component selection.
How to Calculate the Value of Capacitors in Parallel
Calculating capacitors in parallel is very easy. You just add the values from each capacitor.
So if you place a 470 nF capacitor and a 330 nF capacitor in parallel, you’ll end up with 800 nF. You can place as many capacitors in parallel as you want.
The formula for calculating capacitors in parallel makes sense when you think about how capacitors work: A capacitor is basically just two metallic plates, placed close to each other, with an insulating material in between.
The larger the plates, the higher the capacitance. So when you place two (or more) capacitors in parallel, it’s more or less the same as using bigger plates.
Voltage Across Capacitors in Parallel
The voltage across capacitors connected in parallel is the same for each capacitor. If you know that there is 5V across one capacitor, it means that all the other capacitors that are connected in parallel with this also have 5V across.
This isn’t specific to capacitors. Any type of component in parallel will have the same voltage for all the components. If this sounds like a mystery to you, I recommend reading up on the basics of voltage and current.
Why Connect Capacitors in Parallel?
The most common reason for connecting capacitors in parallel among hobbyists is simply that you don’t have the exact capacitor value needed.
Let’s say you want to build a blinking light circuit that blinks at some specific rate. You’ve calculated that you need a capacitor of 147 µF. In your component box, you don’t have this value, but you have 100 µF and 47 µF.
Well, just replace C1 in the circuit above with a 100 µF and a 47 µF capacitor in parallel, and you end up with a total capacitance of 147 µF.
Another typical place where you’ll see capacitors connected in parallel is with microcontroller circuits. Microcontroller chips often have several power pins. And it’s common to place a capacitor from each positive power pin to ground.
In this case, the point isn’t to get a new capacitor value, but instead to show you how many capacitors you’ll need for the circuit. Although they are connected in parallel, they’ll be distributed across the board.
Summary
To get the total value of capacitors connected in parallel, just add up the value of each. Ex five capacitors of 1 µF become 5 µF. And three capacitors of 100 nF become 300 nF.
For simple circuits, you usually only place them in parallel if you need a specific value that you don’t have available.
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