Control Hub and Power Management

[Tom Eng]

Hi Folks - The new Control Hub is not powered independently by a separate battery like a smartphone Robot Controller is. As a result, for teams who will be pilot testing the Control Hub this season, power management of the main battery will be especially important. Teams will have to be careful to avoid dips in voltage that could have an adverse effect on the operation of the Control Hub. Theoretically, if the voltage dips low enough (for example, if a couple or more motors stall during a match), the voltage dip could brown out the Android Controller and cause unknown behavior.

Also, the Control Hub's Android controller constantly draws power from the 12V battery, so teams will have to account for this additional draw when figuring out what their consumption rate is and how frequently they should recharge their batteries.

Teams should monitor their robot voltage during an event, and swap out or recharge a battery that has discharged to the lower end of the acceptable voltage range. Fortunately, the new Control Hub boots very quickly (between 15 to 18 seconds) so swapping out a battery shouldn't be too disruptive.

Tom

[4634 Programmer]

Does the power regulator circuitry on the new Control Hub have a few large capacitors or anything on it to at least help with extremely short (a few ms) voltage drop spikes?

[Alec]

Hi Folks - The new Control Hub is not powered independently by a separate battery like a smartphone Robot Controller is ...

Sounds like the Control Hub needs to be powered independently by a separate battery like a smartphone RC is, especially for pilot testing purposes. Reducing the number variables or complications should make for a more effective pilot test.

[Alec]

Sounds like the Control Hub needs to be powered independently by a separate battery like a smartphone RC is, especially for pilot testing purposes. Reducing the number variables or complications should make for a more effective pilot test.

I just realized the SBC and the Lynx module cannot be powered separately, so scratch that idea.

[Tom Eng]

Does the power regulator circuitry on the new Control Hub have a few large capacitors or anything on it to at least help with extremely short (a few ms) voltage drop spikes?

I believe the CH's voltage regulator can tolerate a pretty wide (and low) input voltage range.

Note that in our testing we've (inadvertently) run the battery low (so it was in the orange-ish zone on the Driver Station... < 10V) and it seemed to work properly in spite of the lower input voltage. However, we did not test the scenario where the input voltage experienced a brief (on the order of a few ms) but significant voltage dip.

I'll reach out to REV Robotics and see what they say. I think as a general rule, however, if teams keep their battery charged and avoid stalling multiple motors simultaneously (which is bad for a number of reasons) they should be OK based on what we've observed during our previous rounds of testing.

[4634 Programmer]

I believe the CH's voltage regulator can tolerate a pretty wide (and low) input voltage range.

Note that in our testing we've (inadvertently) run the battery low (so it was in the orange-ish zone on the Driver Station... < 10V) and it seemed to work properly in spite of the lower input voltage. However, we did not test the scenario where the input voltage experienced a brief (on the order of a few ms) but significant voltage dip.

I'll reach out to REV Robotics and see what they say. I think as a general rule, however, if teams keep their battery charged and avoid stalling multiple motors simultaneously (which is bad for a number of reasons) they should be OK based on what we've observed during our previous rounds of testing.

So in the majority of cases it sounds like it will be a non-issue. Another thing that worries me though is when stalling multiple motors simultaneously is unavoidable in the heat of a match. For instance, my team went to an off-season tournament about a month ago, and during the semi-finals one of our opponents was attempting to shove us around as we were lining up to score. (Yes they came very close to getting a yellow card but that's beside the point). The point is that as all 4 of our drivetrain motors were fighting to keep our robot in place while our dumper arm was simultaneously extending, and the voltage on our freshly-charged, competition-only battery (that was bought new at the start of the season) actually dropped to around 8 volts for more than a second. My fear is that the voltage regulator in the SBC on the CH might dropout in that scenario.

[Tom Eng]

So in the majority of cases it sounds like it will be a non-issue. Another thing that worries me though is when stalling multiple motors simultaneously is unavoidable in the heat of a match. For instance, my team went to an off-season tournament about a month ago, and during the semi-finals one of our opponents was attempting to shove us around as we were lining up to score. (Yes they came very close to getting a yellow card but that's beside the point). The point is that as all 4 of our drivetrain motors were fighting to keep our robot in place while our dumper arm was simultaneously extending, and the voltage on our freshly-charged, competition-only battery (that was bought new at the start of the season) actually dropped to around 8 volts for more than a second. My fear is that the voltage regulator in the SBC on the CH might dropout in that scenario.

I spoke to REV yesterday. They said the suggested input voltage to the CH ranges from 8 to 15V DC.

We also talked about the power surge scenario. They said they have done a fair amount of testing where they momentarily dropped the input voltage very low (less than 5V) to see if a brownout condition would occur. The brownout voltage that they saw was very low and they feel confident that provided the teams have a reasonably fresh battery, the CH should be fine in most scenarios (including the scenario you described).

I think teams will be good to go for most reasonable situations. This is consistent with what we have observed with the current and also past incarnations of the Control Hub.

For more details about their voltage regulator specs, please reach out to REV's support team.