I thought this was important enough to start a new thread so here goes…
Over the last two weekends I have had the opportunity to inspect many robots that have been tripping circuit breakers. In all cases I was informed by the team members that they were tripping due to current overload. When questioned though most reports were that the breakers tripped when in shoving matches or when grabbing a goal. With a few when just running all by themselves. Additionally most teams reported never having tripped in practice, only in competition.
So this is what I observed…
The majority of robots that tripped had their breaker hard mounted to the robot frame.
If a team used the #6 wire to cushion the breaker, the breaker was mounted vertically (i.e. wires out the top and bottom.)or the wires were not flexible.
The teams had aggressive tread design or tank treads that caused a lot of vibration when running.
The team play strategy was to “bang” a goal out of position.
The robot had a high center of gravity or short wheelbase causing some bouncing while running.
Of the robots I observed, vibration or impact were involved in some form or another in every case. Some robots tripped just running from one side to the other on the second day. (This I am guessing is in relation to the carpet getting beat up over the course of a competition and causes an irregular surface.)
I still cannot point to current tripping as a possibility. It may be a contibuting factor in some robot designs made worse by vibration. One team who suspected they were tripping on overloads and were replacing breakers every few matches graciously opened one for inspection. No major defects were noted, but the design of the breaker would suggest that heat, vibration, and current could all contribute to a trip condition and very likely multiple vibrations or impacts would make tripping more likely.
One final note, in the case of one team, the wire clamp on the circuit breaker was loose. Loose connections on high current wires cause heat and the heat from that connection was transmitted to the thermal cutout in the breaker and tripped it off. Tight wires and no more trips.
Hope this helps. If you have had problems tripping breakers and are going to nationals, I’d like to see your robot. I am usually in our pit, just stop by.
Good Luck All
I don’t really think it’s the banging thats tripping the robots. Our robot is a, quite frankly, kamikazee. We ran out of weight for a claw mechanism, so all we have no is really powerful/fast drive system. Guess what we use it for - running into other robots… and hard (team 596, the Sci-Clones can attest to that - at the nyc regional, we kinda bent one of their pnumatic cylinders. But don’t worry, there are no hard feelings between us - actually we picked them as our alliance partners =D).
Anyways, at the SPBLI Long Island regional, we were tripping our main breaker like mad. During our practice rounds, we were flipping the breaker every few minutes. This was fixed by drilling some bolts into our thick wheels and actually decreasing their surface area (see what we mean here ). The wheels themselves were dragging while turning (tank-steering), and this was over-working our motors. This fixed our main breaker problems.
Even so, practically every other round during the actual competition, our main breaker flipped and we sat there. We were ramming a lot, and that probably contributed to it somewhat, but our main problem was with the drive train. We have the opportunity to go down on treads (for uber-power). Turns out this was our problem. The treads seemed to have too much friction moving. Some of our idlers didn’t spin that well, and so (I think this is how you describe it) the motors were working too hard. Bam - we lost power. Anyways, at the NYC Regional, we added some bearings to our idlers so that they spun like a dream, and presto - our breaker problems were no more.
Few robots were banging as hard as we do. Look at the scratches on the front plate in the above picture, we bent some Bosch extrusion, heck, we even chipped some lexan - who knows what we did to other robot (again, sorry 596) =D Anyways, what it comes down to is that although banging did have some effect on the breaker, I suggest that if your still having breaker problems after hanging the breaker loosely and perpendicular to the front of the robot, you look into your drive train, not your playing tactics.
Ok…I am not an electrical person and this is basically all copied and pasted from an email i recieved about our breaker problems…this may help some people…
I’ve picked two of the five breakers as being much better performers, these two
>go about 45% longer at 120 amps, compared to the worst breakers.
>
>COLD SPRAY WORKS
>Precooling the breaker provides 60% more duration on the first power cycle.
>This rises to 120% more duration on repeated power cycles at 5 minute intervals
>(to simulate the high cycle rate found in finals competition). Bottom-line: a
>10 second blast of cold spray will restore the breaker to its original
>performance even if it has just been overloaded. Where do we get more of this
>stuff. I’ve used my only can during this test?
Suspend our best circuit breaker by the 6 ga. wire and 2-4 strips of latex
tubing, directly between the battery and the power panel
Possibly move the power panel closer to the battery (or the battery closer
to the power panel) so we can cut down the length of 6 ga. wire.
Ok…it’s me again…i know our final solution to our problem was that we did some electrical work…mounted the breaker onto a flexible/bouncy kind of V shaped lexan strip…and we really use the Cold Spray…
Our breaker is mounted vertically on the piece of wood in the center of our robot where all our electronics are. We are an aggressive 2 goal grabbing robot and we’ve gotten into a lot of pushing matches and we’ve had some hard impacts (so hard that we bent our goal latch once) and our breaker has never tripped.
Maybe the wood dampens the shock, but who knows.
We haven’t actually measured the amps we pull during pushing matches, but we use a dual-motor drive train, we transfer the weight of the goals, and our treads have a high coefficient of friction and we still haven’t tripped it.
Yes, as SDM said above, we had lots of problems at our first regional. We tripped both the main breaker and the 20 and 30 amp ones. So, if our robot wasn’t moving in jerks across the field, it was dead. Anyways, we really cut down on the friction at NYC (second regional for us) and we had a huge power increase. Not only did we stop tripping breakers (any of them) we had a huge increase in the speed and power of our robot. As Dan said, if the problem is not electrical, make sure your drivetrain has as much graphite, nylon washers (to reduce friction and contact between parts), and anything else that might produce friction. You’ll be amazed at the amount of power that your robot now has. I know i was.
Also, make sure your frame is not grounded (by the light or anything else) cause that was tripping some bots i saw.
As a quick fix, we unscrewed our breaker from the frame, laid a piece of latex tubing down flat where our breaker was, and screwed the breaker back down on top of the tubing. This whole operation took less than five minutes, and we never had the breaker trip after that.
We had lots of problems with the main breaker tripping due to impact. After changing it’s orientation and cushioning it, the problem of impact was gone. We did, however, trip the breaker due to current: We were alone in the mid-field (thus, no chance of impact), with 2 drill motors, 2 chapuia, 2 seats, the light and the compressor on. Will never happen again, but it is indeed possible to trip it by current.
Anyways, we really cut down on the friction at NYC (second regional for us) and we had a huge power increase. Not only did we stop tripping breakers (any of them) we had a huge increase in the speed and power of our robot. As Dan said, if the problem is not electrical, make sure your drivetrain has as much graphite, nylon washers (to reduce friction and contact between parts), and anything else that might produce friction. You’ll be amazed at the amount of power that your robot now has. 