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Unread 09-03-2003, 22:28
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 1996
Location: Wheeling, IL
Posts: 10,792
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Wow, you guys posted a lot in a short period of time. So here goes...
1. These batteries hold up pretty well even after being subjected to low temps. As long as the gell hasn't frozen so badly that the case is warped then I wouldn't really worry about the cold. (The battery heats up pretty quick when in the robot driving around!)
2. Batteries will read in 13-13.5 volt range immediately after coming off the charger but will drop after removed. The definitive test is to put the OI into battery monitor and watch the battery voltage while you drive around. (i.e. press the "select" button on the OI until the display shows something that looks like voltage, like 12.5.) This is a recommended practice whenever on the playing field and have your driver or human player monitor during matches. If the battery voltage gets low, determine what conditions causes it and avoid them. Tight turns, particularly with four wheel or tank tread designs, draw immense amounts of current. When the battery voltage falls below 8 volts for longer than a moment, the robot controller will reset. During reset you will be out of commission for at least two seconds and the rotating light will be off until the controller has reinitialized.
3. The "chalupa" motors are very powerful when used at their design speed and torques. Unfortunately running them at speeds slower than their peak power output will stall the motors in many cases or will not give enough power to climb the hill. Teams should be very careful when comparing practice at home to official fields at competitions. An inch or two in length or height errors can vastly affect the angle of the ramp. The official FIRST structures are the only one that matter.
4. To Team 190, even if nothing is running on the robot except the light and the controller, other systems are drawing current. The light is much lower current draw than last year but the motor and light do draw current. So do the speed controllers, fans, light sensors, and if you are tethered, the OI and operator controls as well.
4. "Slowly fading power, light remains on and speed controllers still on but no function" This sounds like a really bad one. I would at first ask if the radio modems were showing any fault lights. If they were OK, I would check on your primary wiring, i.e. the connections between the main circuit breaker and the circuit breaker panels. If you loop power from one to another, try to isolate which parts of the robot are failing and see if that points to one panel. Check all return wiring (i.e. the wires that go back to the negative terminal of the battery.)they are as important as the positive wiring. The slow fading may be due to electronics heating up with time so check for warm components. Finally, I would take a look at the OI controller and/or power supply.
Lastly, just as an observation and to repeat from the Robot docs
The motors supplied with the Kit of Parts have various power and speed capabilities. Some are quite
powerful and draw very high current when loaded to their limits. Others have very high-speed
capability. Some have integral transmissions that magnify their torque output. Some are equipped
with selectable two-speed transmissions. Before choosing a motor for a particular use, be sure you
thoroughly understand the characteristics of the motor.
Drill motors have an internal cooling fan that is not effective at low motor speeds. Do not operate
the Drill motors at the stall condition because they will quickly overheat and fail.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.

Last edited by Al Skierkiewicz : 09-03-2003 at 22:34.
 


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