Re: Banebots RS-775 Case Short
 

Under Voltage Lock Out. This is the generic term for a processor or device shutting itself down when it doesn't have sufficient voltage to guarantee correct behavior.

Re: Banebots RS-775 Case Short
 

Eric,
The PD is very well designed and works very well. Without any valid data I cannot tell you which trips first since the effect is the same, that is Crio reboot. With the relatively low impedance of the motor wiring back to the PD compared to the higher impedance of the Crio power wiring, it would appear that the majority of the fault current would flow back through the motor wirin when we first observed this fault, we were prototyping with a small motor that we had removed from a battery operated vacuum. The motor case was intentionally wired to one of the wires. I don't think the motor drew more that 10 amps.

Re: Banebots RS-775 Case Short
 

An update from 222. Our shooter using 2 775s has been working flawlessly. We have been periodically checking the 775s to make sure they check out ok. We've put about 60-70 shots through it between last week and this weekend. So far so good.

Re: Banebots RS-775 Case Short
 

Same here! 256 has had no problems with our 775's.

Re: Banebots RS-775 Case Short
 

On a more positive note, I received 6 RS-775-18's today from Banebots. All test out fine!

Re: Banebots RS-775 Case Short
 

2175 has had 775s chugging through some shooter tests that we "borrowed" from last year's robot, and they've had no problems so far. Haven't done any case short tests since we first got them last year. However, because there are so many other motors available, we're going with 550s on the competition shooter just to avoid the headache other teams have experienced, and keep the 775s around for other testing. The 550s are just 20W less powerful than the 775s, and we think we can get by.

Re: Banebots RS-775 Case Short
 

Although I doubt you'll be running them at max power for any length of time (at least I hope not), let's do some numbers anyway just for grins:

at max power of 251 watts, the 550-12 generates 267 watts of waste heat.

at the same power output of 251 watts, the 775-18 generates only 141 watts of waste heat.

the mass of the 550-12 is 218 grams. the mass of the 775-18 is 337 grams.

the ratio of waste heat to mass is therefore

550-12: 267/218 = 1.22

775-18: 141/337 = 0.42

Re: Banebots RS-775 Case Short
 

Yep, these are going somewhere where they're seeing mostly intermittent duty (not at max power when free wheeling, probably powering shooter down when collecting balls), so we aren't concerned about the heat. But it's interesting to see that comparison.

Re: Banebots RS-775 Case Short
 

Has anyone received any 775s recently who can comment on the condition in which the motors arrived?

Re: Banebots RS-775 Case Short
 

We received 12 RS-775-V18 motors.

Test ran unloaded for 20 min
Checked for Case Short - none

Then we started using one on the shooter.. After some testing, case shorting was detected. That motor is begining to degrade and run at a higher temperature. We plan to use it till it drops. We want to develop a replacement and reliability plan for the motors in this application.

We implemented modifcations to improve cooling of the motor based on of the other threads. These included a spacer between motor and the CIMulator to permit air flow into the motor and cooling fins on the motor case.

Re: Banebots RS-775 Case Short
 

Team 907 has just received two RS-775-18's
One has a case short.

so, 50% failure rate
:mad:

Andrew Paul
907 Mentor
EYCI

Re: Banebots RS-775 Case Short
 

re motors coming from factory shorted

Wow. Even after last years feedback, the manufacturer has still not solved the problem. Worst still they apparently are not even doing simple QA tests on them before shipping. We (or Banebots) need a new motor supplier. I have 6 of these on order and I can't see how I can risk using them.

Re: Banebots RS-775 Case Short
 

As Banebots has pointed out, they do run tests on their motors before shipping them out and advise any teams who receive bad motors to contact them asap. It's my opinion that motor defects upon receipt are the result of poor packaging (the shipment of 775s we received yesterday had pieces of broken Styrofoam, which I assume was there hold the 775s stable during transit).

We received a shipment of 4 775s yesterday, none of which had case shorts and were fully functional.

Re: Banebots RS-775 Case Short
 

This problem has been notoriously intermittent, and I don't know of a good way to know whether a particular motor doesn't have the issue. Detecting a case short is a certain way to know that there is a problem, but not detecting the short doesn't mean that there isn't a problem. Rotating or jostling the motor can hide or expose the defect.

I'm of the opinion that the "case-zap" method doesn't fix or clear anything, it just shakes things up hard enough to push the defect back into hiding for a bit. It can then pass bench testing until something else causes it to express again.

I'm willing to believe that Banebots is performing best faith QA, and that the defect is too finicky to be caught by their testing. My suggestion is to teams is to treat all of these motors as defective regardless of testing and isolate them appropriately or switch to a different motor.

Re: Banebots RS-775 Case Short
 

Team 3135 placed initial order for a pair of CIM-U-lator=>775 gearboxes recently (on Feb 1st)), along with a total of four 775 motors. Because of the internal shorting problem, we wanted to have spares.
Expecting at worst maybe one in four to test bad, our order arrived today with THREE SHORTED MOTORS (zero ohms) out of four. We are bailing out on using the 775 motors for ANYTHING EVER AGAIN. I hope we can get a replacement pair of DUAL 550 CIM-U-lator gearboxes shipped ASAP. Banebots may be testing these 775 motors, but if so, USPS is killing them in transit. Packing was adequate but not very good considering the known issues. The motors should have been rolled up with multi layer bubble pack surrounding them, and they were not.

FOLLOW-UP - GOOD NEWS
Banebots agreed to send us by overnight ship two back plates that would let us convert the CIM-U-llator gearboxes over from RS775 to RS550 (single or dual). Right now it's only for lack of the big gears and output shafts that is slowing down CIM-U-lator deliveries, but the aluminum plates are in stock. So, this lets us use dual 550 motors instead of 775s.
So, they sold us the two back plates for the price of one complete CIM-U-lator, and 3 extra mounting kits were also included.
BTW, for those waiting for 550 CIM-U-lators to ship, they would not move us to the head of the queue to swap a single 550 CIM-ulator gearbox for our one unusable 775 gearbox simply because of the three shorted 775 motors, even though we offered to overnight return the one of the 775 CIM-U-lator to get a 550 replacement. They understood that we no longer trusted using 775 motors, even free replacements, so, instead they proposed getting us the 550 backplates .
With this compromise, we are happy and feel taken care of by Banbots.

-Dick Ledford