IME questions ???

[e-LEMON-ators_5119z]

Hi everyone, i wanna get some IME’s for our drive as fitting quad encoders is gonna b very hard

now from people i know they said that IME’s gave them alot of trouble (especially with their cortexs, all 3 of them)

please if you have IME’s, can you post with your experiences

Thanks In Advance

[Ephemeral_Being]

I’m curious what you mean “with their cortexes, all 3 of them.” That doesn’t even make sense.

We like the idea and ease of programming with IMEs, but had problems with the static problems that everyone read about before Worlds. It was about 1/20 times that the routine would fail, the IMEs would lock up, and we would need to do a power cycle to get everything working again.

I heard that RobotC has some sort of safeguard to prevent the problems we had in EasyC. I’ll go pull up the information from some earlier topics if I can find them.

[e-LEMON-ators_5119z]

to clarify … whenever they had IME’s plugged in, it would make there cortex’s not work … all 3 of them … they ended up scrapping them

and thanks !

[Ephemeral_Being]

to clarify … whenever they had IME’s plugged in, it would make there cortex’s not work … all 3 of them … they ended up scrapping them

and thanks !

No, that didn’t happen to us. None of our Cortexes have been ruined by using IMEs.

Alright, here’s the information that I was looking for. jpearman explained this way better than I ever could. You should have very few problems if you follow his advice below.

What can I do to reduce the static problem?

The fields at worlds will be treated with anti-static spray, I think static will be a non issue, however, for the ROBOTC users…

Upgrade to V3.60, spurious I2C communication issues have been reduced by a factor of 10.

Again, upgrade to V3.60.

For the EasyC users, switch to ROBOTC

V3.60 will also help with condition 1 above as it contains a watchdog timer set to 750mS, if the cortex crashes the code will be reset and control may be regained, however, note the warning here.

In addition, write software that can tolerate imperfect IME operation, always use a timeout when driving based on encoders, monitor the encoder values if you see a large negative (or positive) jump when there should not be one then take some alternative action. Some of these types of things I covered in this post, although that was not specifically aimed at IMEs.

And here’s some more links.

https://vexforum.com/t/esd-my-thoughts/23332/1

https://vexforum.com/t/ime-technical-description-and-software-workarounds/23218/1

[e-LEMON-ators_5119z]

thanks ! <10characters>

[Ephemeral_Being]

thanks ! <10characters>

Sure. I think we’re going to be using the full ten this year. Hopefully a bunch of people will be, too. They’re really handy. Just keep in mind, the 4-wire extension cables and 393 IMEs are more expensive than the sensors that you would have otherwise used. It does free up more slots on the Cortex’s sensor ports, though.

Just for reference,

http://www.vexrobotics.com/vex/products/accessories/sensors/276-1321.html

http://www.vexrobotics.com/276-1949.html

[jpearman]

Sure. I think we’re going to be using the full ten this year. Hopefully a bunch of people will be, too. They’re really handy. Just keep in mind, the 4-wire extension cables and 393 IMEs are more expensive than the sensors that you would have otherwise used. It does free up more slots on the Cortex’s sensor ports, though.

Just for reference,

http://www.vexrobotics.com/vex/products/accessories/sensors/276-1321.html

http://www.vexrobotics.com/276-1949.html

Bear in mind that ROBOTC only allows 8 IMEs, not sure about EasyC. As more IMEs are added the update rate for each one will be reduced, not so much of a problem for ROBOTC as it polls them around 1000 times every second, more so for EasyC as it polls them much less often.

If you have multiple motors on a lift system then I would only encode one of them with the assumption that all motors should move together.

[Ephemeral_Being]

Bear in mind that ROBOTC only allows 8 IMEs, not sure about EasyC. As more IMEs are added the update rate for each one will be reduced, not so much of a problem for ROBOTC as it polls them around 1000 times every second, more so for EasyC as it polls them much less often.

If you have multiple motors on a lift system then I would only encode one of them with the assumption that all motors should move together.

I… did not know that…

Thanks.

[ajo518]

We had lots of problems with them under RobotC, but I believe that was before the update. I believe that we had a problem with static mainly because of our robot design that greatly increased the number of problems that we had. After 2 days of attempting to get them to work we switched to quad encoders, so we didn’t give them too much of a chance. We hade consistent failures when using them. I did not write the code so it could have been that as well. If you want it to just work then I would stick with quad encoders. If you want and are able to put in the time to get them to work, then I would use the integrated encoders. I believe that most of the problems have been greatly reduced if not eliminated from the integrated encoders.

hope this helos:D

~Andrew