Instant AC Power Filtering

By Jeff Faust
Category: Arduino
Difficulty: Easy

You’ve been working hard at your Arduino-based servo project, and so far it’s working great. Time to untether it from your computer and let it run on its own, right? It works fine on USB power. It works fine on a 9-volt battery (while it lasts). You plug it into an adapter and…twitch…twitch…twitch. Suddenly it’s not functioning anymore. Damn!

If the adapter voltage is within range, and current supply is adequate, your problem is likely filtering: the adapter is not eliminating the ripple voltage, and that’s interfering with the Arduino’s ability to control the servo. Here’s a quick way to clean up your power and get your project moving again.

Steps

Project Steps All
1. Carefully bend the capacitor's leads...

Step #1:

Carefully bend the capacitor's leads as shown, so that they can be inserted into the header without fouling other wires or components.
The positive lead is inserted into V_in; the negative goes to GND. I'm using a Seeed Protoshield for my project. The capacitor may be attached to the appropriate pins of the shield, or to the Arduino itself.
Inspect your connections one more time to make sure that nothing will short out, then attach your adapter. Your project should work fine.
Note that I'm using a 2200uF capacitor here--that's probably oversized, but it's getting the job done.

2 Responses to Instant AC Power Filtering

Mateus on February 3rd, 2013 at 6:42 pm said:

Where is it?

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Mike on February 11th, 2013 at 10:26 am said:

The implementation details have been left as an exercise for the reader.

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