cRio Constantly Rebooting

[Al Skierkiewicz]

Dale,
So we all get on the same page here...
Only four CIMs are allowed on the robot. CIM stall is 133 amps. Battery can supply 500 amps for a few seconds, although I would guess closer to 600 on newer batteries. (also the spec on MK batteries is 750 amps) Battery internal impedance is 11 mohms (.011 ohms), #6 is .0005 ohms per foot. Figure the same loss the Anderson connector, main breaker, and terminals on the battery and PD and you are likely pretty accurate on the total losses. I would guess that .015-.02 ohms would be pretty close.
The battery connection on the analog breakout in Crio slot 1 monitors battery voltage and inhibits Crio output when the supply voltage falls below 5.5 volts. The internal power supplies on the PD (+24, +12, and +5) drop out around 4.5 volts. If the voltage droop is sufficiently low and sustained, the Crio and radio are likely to reboot. The Crio will take about 30 seconds or more (typical) while the radio takes 52 seconds minimum. The power supplies are independent. The Crio is speced to work down to 19 volts and the +24 volt load will affect this power. This includes +24 volt solenoid valves and sensors. Please remember that battery temperature also affects the amount of available current as well as internal impedance.
While a second battery would help, most teams do not need it and play fine without brownouts.

Jared, after watching the videos I believe the Crio and in one case the radio as well are rebooting. I commented in my reply but if you would like to tell here what drive train you are using, I can reply here as well.
AL

[The Lucas]

Originally Posted by Jared341

Other teams have used successfully 6-motor drive setups geared for similar speeds in the past, but as you pointed out, this was in the IFI era when we often had backup batteries (even before backup batteries, does anyone have data on how low the main battery has to go before the RC reset?).

I have anecdotal data about the pre backup battery from 2002. MOEhawk our 2002 bot was geared for in my estimation well over 20fps (seriously it was the fastest top speed FIRST Bot I've seen including '08 lap bots) with 2 drill motors and 2 CIM (traction wheels in back, homemade omnis in front in the days before Andymark ). It employed a 3 goal grabber strategy similar to 71's legendary bot, so the fast drive train was only intended to be used in the first couple seconds. After that we would anchor down (didn't have shuffle drive like 71) for the rest of the match.

At VCU, we noticed the 4 motors would drop the battery votage to <5 and the IFI controller would reboot into some sort of Safe Mode where the latency between joystick commands and actions was very long (again this what I remember about a weird problem many years based paritailly on driver observations so take it with a grain of salt). It also blew fuses on the IFI controller. At VCU, We re-geared the drive a bit slower to fix this problem (and also because our 14 ft wingspan had not fully deployed in the time we could hit the goals so we had to slow down). On ship day, we just finished the massive bot (including deburring hundreds of lightning holes), drove it with the moto "Don't break it" and stuck it in the crate. Let this be a lesson to drive your bot hard before shipping to find problems (or as we call it Break Robot. Re-engineer. Repeat! ).

[Jared Russell]

Originally Posted by The Lucas

Let this be a lesson to drive your bot hard before shipping to find problems (or as we call it Break Robot. Re-engineer. Repeat! ).

That is the only part that doesn't make sense to me about the "simply too much power" theory.

We drove this thing HARD for 10 days prior to ship. For far longer than 2 minutes at a time. With brand-new, not run-in gearboxes. With brand new treads, and with an even faster gearing on our arm (I remember the FP getting HOT to the touch during practice - we increased the reduction in our competition bot so that it barely gets warm to the touch now).

All the math, intuition, and experience says that the problem is drawing too much current. But I can't figure out why, for the life of me, we didn't have any problems until midway through the regional.

[Alan Anderson]

Originally Posted by Jared341

All the math, intuition, and experience says that the problem is drawing too much current. But I can't figure out why, for the life of me, we didn't have any problems until midway through the regional.

Maybe one (or more) of your electrical connections has degraded and is dropping more voltage than it used to.

[Al Skierkiewicz]

Jared,
Your carpet and the new playing field carpet are likely much different as far as friction goes.
Brian,
Pre-backup battery IFI controllers would drop out at 7.5-8 volts due to the need at the 5 volt regulator for a minimum 2.5 volts of differential input to output specs as I remember.

[The Lucas]

Originally Posted by Jared341

That is the only part that doesn't make sense to me about the "simply too much power" theory.

We drove this thing HARD for 10 days prior to ship. For far longer than 2 minutes at a time. With brand-new, not run-in gearboxes. With brand new treads, and with an even faster gearing on our arm (I remember the FP getting HOT to the touch during practice - we increased the reduction in our competition bot so that it barely gets warm to the touch now).

All the math, intuition, and experience says that the problem is drawing too much current. But I can't figure out why, for the life of me, we didn't have any problems until midway through the regional.

I was really putting MOEhawk up as the lesson for extreme testing before ship, not your current bot. We finally got MOEhawk all together (we tested components before), ran it at half speed into the 3 goals and said "Ship It" (it was getting late). Question on your testing, are you simulating defense with an old bot (high speed collisions and pushing matches)? If I remember FL well enough you were seeing your share of D and tended to fail later in matches after everything got hot.

I am always amazed how Team 25 has so few over current issues with their drive train (they had a few notable ones early like on Einstien '03). They have mastered the 4 CIM fast single speed with 6-8 Bead-LOK wheels on the floor. It has to be some combination of good driving, gear box efficiency, and good use of the brake pin.