HELP: Voltage Drop

[pujan824]

When testing our robot, we were getting a voltage drop to 6V when going over the obstacles. When going over the carpet we have been dropping voltage to 9V.
Our robot has 6 8" pneumatic wheels powered by 2 cims in a toughbox mini each controlled by a talon srx
It has 2 window motors for lifting our arms each controlled by victors
2 mini cims for shooting each controlled by talon srx. (we are planning to swap these out for banebots RS-775 or 775pros )
We also have noticed the front CIMs on our drivetrain getting really hot.
Our drivetrain does not have the center wheel dropped.
Currently we do not have the time to create a center wheel drop.

[MrTechCenter]

What's your battery voltage when you're not moving (idle)?

[techhelpbb]

With all these topics on power draw I am really surprised to not see any current readings from the PDB. With voltage and current it would be more clear what is drawing all that power.

[pujan824]

Originally Posted by MrTechCenter

What's your battery voltage when you're not moving (idle)?

It's at 12.5 V

[pujan824]

Originally Posted by techhelpbb

With all these topics on power draw I am really surprised to not see any current readings from the PDB. With voltage and current it would be more clear what is drawing all that power.

We just checked and its from the drivetrain cims. But the front cims are drawing the most power while the back cims aren't anywhere near that

[techhelpbb]

Originally Posted by pujan824

We just checked and its from the drivetrain cims. But the front cims are drawing the most power while the back cims aren't anywhere near that

So by 'front CIMs' you mean that in if you look at the top of the robot with 2 CIMs in the ToughBox Mini you see this issue only on the CIMs closest to the front of your robot?

Are the wires to the 'rear CIMs' much longer than the 'front CIMs'?

[kdavidson]

Are both SIMs in each Toughbox pair being driven in the same direction? If they are fighting each other, I wouldn't be surprised to see this. We always run one at a time as a first test to make sure they are going the right way.

Ken

[Ether]

Originally Posted by pujan824

Our robot has 6 8" pneumatic wheels powered by 2 cims in a toughbox mini

With what gear ratio?

Our drivetrain does not have the center wheel dropped.

We also have noticed the front CIMs on our drivetrain getting really hot.

We just checked and its from the drivetrain cims. But the front cims are drawing the most power while the back cims aren't anywhere near that

Please post the actual numbers, and include what command was being given to the CIMs.

Did you guys do any calculations before selecting wheel diameter and gear ratio?

[Jon Stratis]

I would say the most likely issue is using 6 pneumatic wheels without a drop center. That's a whole lot of scrub when you try to turn, and that will eat your battery like you wouldn't believe.

[techhelpbb]

Is there a troubleshooting flow chart for this?

I mean I can easily find 6 topics on related issues.
Maybe it's time someone makes a troubleshooting flow.

[Ether]

This happens almost every year right toward the end of build season.

Maybe the kit of parts should contain a big warning notice on day-glo orange card stock about improper drivetrain gear ratios and oversquare skidsteer bots.

[techhelpbb]

Originally Posted by Ether

This happens almost every year right toward the end of build season.

Maybe the kit of parts should contain a big warning notice on day-glo orange card stock about improper drivetrain gear ratios and oversquare skidsteer bots.

Maybe if GDC says those are the only types of robots allowed in a team update enough people will read that joke enough to get the idea not to do it Reverse design psychology.

In fairness since it happens over and over probably time to crack out Draw.io and make a flow chart.
At least to save myself the CSA size migraine March 4th.

[pujan824]

Originally Posted by techhelpbb

So by 'front CIMs' you mean that in if you look at the top of the robot with 2 CIMs in the ToughBox Mini you see this issue only on the CIMs closest to the front of your robot?

Are the wires to the 'rear CIMs' much longer than the 'front CIMs'?

Yes. That's the issue. And the wires to the rear cim is about the same length as the front cims

[pujan824]

Originally Posted by kdavidson

Are both SIMs in each Toughbox pair being driven in the same direction? If they are fighting each other, I wouldn't be surprised to see this. We always run one at a time as a first test to make sure they are going the right way.

Ken

We have tried that and found that they aren't fighting each other.

[pujan824]

Originally Posted by Ether

With what gear ratio?



Please post the actual numbers, and include what command was being given to the CIMs.

Did you guys do any calculations before selecting wheel diameter and gear ratio?

No we haven't done any calculations but the lead member for team 1241 told us this should be fine for our purposes.