What is an Input Voltage Brownout?

What is an Input Voltage Brownout. In one of my test drives on the robot from yesterday I got 721 of them… Is this normal to get and if not what should I do?

Input voltage Brown out means that the Rio has detected the battery voltage dropping below 6.8V. Basically means your battery is either dead flat, or your bot is pulling some serious current.
Check out WPILib for more info.



would this cause the symptoms I have described in

Yes, if the Rio enters a stage 3 brownout (4.5V), the Rio will blackout and communication will be lost until it reboots.


How should I approach the issue?

Post a screenshot of the driver station log viewer from one of your test drives.
Also do you observe the battery indicator flashing red?


where is this indicator? do you mean the rsl? also, I will post the screenshot and the log files as soon as I have a chance… Thanks

On the driverstation battery readout, the background will go red when the Rio enters a stage 1 brown out (6.8V).

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I would expect to see something like this in the DS log. This specific log recorded 54 brownout events.


How long was your test drive? Was the battery fully charged before you started?

On a previous team, we installed DC panel meters like this on our robots so we knew when we had run the battery down and should change it before practicing more.

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sorry I will not be able to access our driver station computer for another couple of hours… I will send it to you as soon as I can get to the computer. Thanks again for the help!

No problem!

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here are examples of four graphs. The first graph is the one that has 721 brownouts (it is 1,792 seconds in length):

Here is the screenshot of the message telling me about the amount of brownouts… It is the last event in this pic:

To me, it does not appear in the graphs that I am losing voltage, but in the events it does appear that I am having brownouts… Is there anything else that could cause brownouts?

I will attach the riolog files for my four most recent test runs with the robot. Bear in mind anytime it says one of the following in the riolog, it is just me printing out a string every iteration of every command for debugging purposes:

1 ramp
2 ramp
y demogorgon claw
a demogorgon claw
b demogorgon lift
x demogorgon lift

^^ These are the debugging string outputs ^^

Here are the riolog files:

2019_02_16 11_57_06 Sat.dsevents (712.2 KB)
2019_02_16 11_57_06 Sat.dslog (3.0 MB)
2019_02_16 12_27_50 Sat.dsevents (49.3 KB)
2019_02_16 12_27_50 Sat.dslog (927.4 KB)
2019_02_16 13_20_23 Sat.dsevents (149.0 KB)
2019_02_16 13_20_23 Sat.dslog (4.4 MB)
2019_02_16 14_08_38 Sat.dsevents (120.8 KB)
2019_02_16 14_08_38 Sat.dslog (337.7 KB)

Thanks again!


Also, I don’t think this happens in the drivers station. I do not have the robot right now to test it on, but I do not remember this happening…


the test drive with 721 brownouts was 1,792 seconds long

The battery had been charged not long before and we had only already used it for around 3-5 minutes. However, other times it has happened in fully charged and also running low batteries.

And thanks, I will look into this

I’m not sure whether the Rio or the PDP measures the voltage, if it’s the PDP, it may be a loose power wire in the Rio, causing it to brown out but not measure a voltage drop.

This said, I’m not entirely sure what is causing the issue, or if it’s related to your other thread, as a level 1 or 2 brown out shouldn’t drop communication, and a level 3 would take a couple seconds to reboot (And not still be enabled after).

Were you driving your robot around during these tests, if so how hard (ie drawing lots of current)?

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The log doesn’t show input brownouts, it shows communication timeouts.

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  1. Loose battery connections. If your battery terminals move they drop voltage.
  2. Loose main breaker connections. Same as above.
  3. Improperly crimped #6 wire terminal. Same as above.
  4. Loose connections to PDP. Same as above.
  5. Loose SB50 contacts. Most often due to a person bending the spring steel behind the contact to make mating easier. Same as above.
  6. Dirty, pitted or corroded SB50 contacts. Same as above. Inspect the mating surface of the SB50 contacts. If there are scratches then replace with pristine contacts.
  7. If none of the above are #6 gauge minimum wire size, replace as required.
  8. Be sure you have reduced to an absolute minimum any friction in the drive train. Test robot with wheels off the ground and see if you are still experiencing brownouts. Do not expect to turn a wide or long robot with six wheels on the ground. The center wheels must be “drop center” to prevent the drive motors from going into stall every time the robot turns.
  9. If you do not already use ramping commands in your drive software (or some other form of feedback to reduce current) then research and add it.
  10. Be sure you battery charger is fully charging the battery. A simple multimeter voltage test will not determine battery charged state.


so, what would cause communication timeouts?

I was driving, but only running the motors at half speed. And it was definitely not intensive driving…