View Single Post
  #36   Spotlight this post!  
Unread 18-02-2012, 16:16
iambujo iambujo is offline
Mentor
FRC #2729 (Storm)
Team Role: Mentor
 
Join Date: Feb 2008
Rookie Year: 2008
Location: NJ
Posts: 86
iambujo is a name known to alliambujo is a name known to alliambujo is a name known to alliambujo is a name known to alliambujo is a name known to alliambujo is a name known to all
Re: Gear ratios for launcher

Quote:
Originally Posted by iambujo View Post
So we just rechecked wheel speed, and it maxes out at about 3500 RPMs, or 12,991 RPMs motor speed. We measured the voltage across a .01 ohm power resistor and it was about 210 mv. So at max speed it looks like we are drawing about 21 Amps. In-rush current when the wheel starts up peaks out at about 50 Amps for a brief moment.

Now we need to check the motor voltage, maybe that is where the flaw in the applied math is. SW is sending a "1" to the Jaguar, but I guess there is more voltage drop that I expected.

Thanks again for the insight. Everything is working ok, at this point it's just a study of the real world numbers we are collecting compared to the expected data based on the motor curves.
Ok here is a good reason it is good to compare real world measurements to the expected/theoretical numbers. After scratching our heads we asked SW one last time if they were sending '1' to the Jaguar. They said 'Yes. Wait - It's a Jaguar? We have it coded as a Victor'. Opps! Since Jaguars have a larger band of PWM Full/Reverse signal input, that means they really were not sending it a '1'. They changed to Jaguar and now it runs a good amount faster at hight input values and is much closer to the curve.

Thanks for sticking with me on this one Ether!