3 Microcortex Controllers for sale....

Hello guys im selling 3 microcortex controllers.2 are used and 1 is brand new in box.Message me at fatalisim@yahoo.com if you are interested.I also have pics if you request them.Thank You.

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Pm me with a price.

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Used Cortexes could have worn-down circuit breakers, meaning they trip easier. Just a warning to anyone actually considering buying these.

EDIT: I was wrong. See below for more accurate information.

There is no evidence to support this, see post #12 in this thread.

https://vexforum.com/t/ptc-performance-measurements/20872/1

I was talking with the VEX Technicians at Worlds yesterday, and they specifically told me that both the circuit breakers within the Cortex and the Power Expander can become worn-down if tripped too many times. We were having trouble with ours tripping much before they should have during shoving matches, and they indicated the weakened breakers to be the problem. It was fixed by replacing the hardware, so I assume they were correct.

I just read the thread you posted, and it was WAY over my head. I know nothing about how the Cortex Breakers work other than what I was told yesterday. I understand my information is wrong based on your lab testing, but based on what we were told by the VEX Engineer and the results we achieved by replacing the hardware, I am fairly confident that there is something that can go wrong within the breakers after repeated tripping.

Yes but it’s only temporary. Read about the device here: http://en.wikipedia.org/wiki/Resettable_fuse

This quote in particular is what the refs were referring to:

In other words, it will trip more quickly for the next few hours as the device cools down but once it fully resets it’s just like new.

Really? I guess that saves us $400 in not needing to replace a Cortex and Power Expander. I’ll amend and correct my original post with this information.

Thanks for letting us know. I was unaware they would repair themselves. Do you know the exact time-frame? Or just after you trip the breakers 12-15 times to use a different Cortex until the next day?

Depends on the breaker but it’s on the order of a few hours to return to their very original state.

I would suggest not replacing the cortex but rather prevent them from tripping in the first place. Some tips:

  1. Spread out the motors. So, put half your drivechain on one breaker, half on another. Then put half your arm on one, half on another. This keeps your from putting a sudden power draw all on 1 breaker.
  2. Use smart software like jpearman’s: https://vexforum.com/t/smart-motor-library/22282/1&highlight=jpearman . Scroll to the end to find the latest version.

Yeah, the splitting of our second drive train across three circuit breakers apparently caused what we have termed a cascade effect, which basically caused our breakers to trip over and over in sequence if we drove wrong, sometimes 6-8 times a match. I did something dumb, apparently, and no one on our team had realized I had come up with another of my bad ideas. Oh well. It didn’t hinder the robot’s performance for more than one match.

I’ll take a look at the code you posted. It sounds intriguing.

I had expected the PTC devices I tested to degrade even though I could not find anything supporting this idea in the literature or datasheets I had read. I gave up testing after 500 trip cycles because the device seemed to be stable. I’m not sure what you were told at worlds but I would add the following.

I found large differences between different devices in the time taken to trip when operated near the trip point. The first post in the thread I linked had data that showed one device tripping in 48 seconds while another took 123 seconds, almost three times longer. Before replacing your cortex perhaps try some tests of your own, build a heavy pushbot with four motors running on one breaker (say ports 2 through 5), don’t stall the motors but simulate a pushing match and time how long before all motors lose power, try and keep the internal motor PTC from tripping, as this will probably confuse the results, by keeping the motors moving at perhaps half speed, this should use enough current to trip the internal cortex PTC. Try both your units and see if there is a significant difference, make sure they have “rested” for several minutes between tests to allow all the PTCs to recover.

If you find a big difference, VEX can (I assume) replace the PTCs for you for less than the cost of a new cortex. Alternatively, if you have a mentor with the necessary skills it will cost you about $1 in parts to replace them yourself (technically not legal but we have to assume you have the integrity to use identical parts to the ones currently used by VEX).