Capacitors on sensor power rails?

Part of the perfboard I’m using for my first robot is dedicated to sensor I/O. I have a three-row-wide strip of male headers, with common ground and power rails, and discrete pins for reading or writing values.

During the mockup phase of my project, I used a 47uF capacitor to smooth out power to my Sharp IR sensor, which alleviated the noise I was seeing. Would adding a similar (perhaps larger?) capacitor between the ground and power rails perform a similar function for whatever I plug into the headers?


In general, more capacitance on your power lines will help the things attached to those power lines. One drawback to keep in mind is that more capacitors might mean more initial current when you turn things on and things staying on longer when you (try to) turn them off. However, a few hundred uF on your power lines is quite reasonable, so you can probably safely add a bunch more of the 47 uF caps. Whether that actually gets you anything will depend on your application.

- Jan

The Sharp IR sensors draw a lot of power in short bursts as they emit their IR, so this can stress the power rail and disrupt your circuit. Putting a large cap somewhere near your sensor (the closer the better) helps to protect your power rail from these disruptions and improve the performance of the sensor. Capacitors won’t be so necessary unless your other hardware causes similar power disruptions (e.g. if you’re driving a 2 mA LED from the header, you probably don’t need a large capacitor to smooth things out).

- Ben

Awesome. Thanks, guys!