noisy Power Distribution boards

The buck/boost power converters on our power distibution board make a very annoying whine. Moreover, simply illuminating an led is enough to significantly change the pitch of the whine.

For instance, with only the cRIO and one Digital Sidecar powered by the PD board, simply the flashing of the Digital Sidecar’s status led makes the PD board sound like a European police siren.

In a noisy room it’s not so bad, but in the quiet confines of my dining room it is very irksome.

I should say that in this case I am powering it with a 12 V, 7 Amp hour SLA and not a car battery.

Should I expect this? Is there something I can do about it?

We had the same problem too. Once in a while it would go away but we gave up on figuring it out. We think its normal.

Sorry! The boost converters tend to whine when they get bored. It is completely normal, and there isn’t a whole lot to do about it.

The boosts are significantly over-sized for running on the dining room table, because they are sized for running during a match with a low battery*. The downside of this beefiness is that the minimum load for continuous operation is a tad higher than what you are demanding of them. Therefore, they periodically shutdown and wait for the voltage to droop a bit before they turn back on and fill up the caps again. This on / off happens to fall exactly in the painful range of audio. For added fun, the actual frequency depends heavily on the load - erego the police siren effect! During normal (hard) operation, it runs at ~600kHz, well above human hearing. However, during normal (hard) operation, the sound would be drowned out by the noise of the motors and the crowd.

Gen2 is supposed to be slightly less screechy, but honestly it still isn’t perfect. You could try drooping your battery or attaching a dummy load, but I won’t make any promises.

  • They are actually capable of supporting the cRIO and the router at about 3V in on the battery - a fourth of typical.

We like to call it the quantum tea kettle

If you’re just running a programming testbed, with no significant high-current loads, the “high” voltage of a fully-charged battery is going to be an issue. A 12 volt power supply capable of a few amps might work better. (Unless you really know what you’re doing, use a linear supply and not a switching one.)

Interesting you should say that.
Usually when I get that noise loudly, it means my battery is low (I think it starts at 12v, but it may start a little higher.)

I have in fact used a switching power supply. (14v, 9A max continuous) If I have the Robot Radio plugged in when I start the robot up, it hangs around 3v. If I disconnect power to the robot radio, the power supply jumps up to 14v, and I can plug the robot radio in again with no problems.

As a general rule, the more switcher power supplies you have, the noisier it will become. I can sometimes reduce the noise by disconnecting the analog breakout and digital sidecar. (Except for my Black Jaguars, my hardware is 2009, so the Analog Breakout does not have a linear regulator).
Wouldn’t it be nice to be able to disconnect power to the camera and robot radio power supplies when you didn’t need them? I would think a 1A ATC fuse and holder would do that wonderfully.

I also get interesting results with the 14v switcher power supply when I have 9 Jaguars attached; several of them have a delayed startup from brownout.