Powered OI input

[EricS-Team180]

Hi,
With the start of our Fall season, we've been doing some brainstorming on novel operator controls. Given the rules on the OI interface do not allow powered controls, in general, we've been wondering if anyone has ever gotten "special dispensation" from FIRST and would be kind enough to share the circumstances?

I recall a team mentioning that FIRST agreed to a wavier for them, in a past season, but I have searched the archives and haven't been able to dig up the thread.

Thanks,
Eric Schreffler - Team180 SPAM

[Lloyd Burns]

Several years ago, the rules declared that all devices attached to the OI dashboard had to be battery powered. This was clearly overkill, and the sensible statemant would have been "must not require a 110V outlet. They envisioned people bring up laptops needing a plug, which they hadn't planned for.

I had built an PIC + LCD dashboard reader that stole power from a joyport on the OI - a PIC and a CMOS/LCD display, which dragged perhaps 10 mA from the joystick power circuit. Oh, the weeping and wailing and gnashing of teeth, but yes, we could use it, as long as we could demonstrate that it was not controlling a joyport input.

The next year, in the insane time with Yahoo Groups, my request for the same treatment was not refused, just ignored. Guess I should have used it (tacire consentire est.). Since it made no real difference when we were on the field, but really helped when setting up, we returned the favour, ignored First, and used it only in the pit.

[KenWittlief]

the rules state you cant pull any power out of the operator interface, and I think there must be some reasons behind that.

last year we used 4 superbright LEDs on a heads up display, so the operator could see status signals on certain functions on the Bot (arm all the way up, all the way down, that type of thing)

they were connected only to the LED outputs on one of the joystick ports, and we had problems with our link kicking off during the matches, and with the OI reseting itself.

We disconnected the 4 LEDs and the problems stopped.

Might have been a coincidence - we never got to the bottom of it.

[Ian W.]

Can't you just hook up a 9 volt, or perhaps one of the bigger 12 volt latern batteries, and use that? Yeah, it'd be big and a pain to carry, but it'd get the job done, no?

[FotoPlasma]

Originally posted by KenWittlief
the rules state you cant pull any power out of the operator interface, and I think there must be some reasons behind that.

last year we used 4 superbright LEDs on a heads up display, so the operator could see status signals on certain functions on the Bot (arm all the way up, all the way down, that type of thing)

they were connected only to the LED outputs on one of the joystick ports, and we had problems with our link kicking off during the matches, and with the OI reseting itself.

We disconnected the 4 LEDs and the problems stopped.

Might have been a coincidence - we never got to the bottom of it.

Could the LEDs have been drawing too much current? The LED output pins on ports 1 and 3 of the OI are only rated to source 10mA. I just did a quick google search, and some of the superbright LEDs I saw are supposed to draw 20mA+.

Ian: If I were going to do something requiring it, I'd probably get a 9V battery enclosure, and just make sure to have a few on hand.

[Ian W.]

I'm extremely stupid.

We did this last year with a "control box" with a human/auto mode switch and a, well, big red button. We also put in three LEDs, which were unable to draw power from the OI because we either couldn't figure it out or we were drawing too much. So Dan, who built this little box, soldered a 9 volt battery in. Of course, that worked great, till the battery died.

So, lesson, 9 volts are good, just don't solder them directly into a circut .

[Lloyd Burns]

The lesson is that batteries are good, but a source of continuous power is better than even a continous source of fresh batteries. For my circuit, having assured myself that the draw would be small enough, I even got IFI's ok, before requesting the august ones' blessing.

I was drawing power from the power to the multiple 100k joypots, which was on a relatively huge fuse, for the load I was drawing. ON THE OTHER HAND, the LED outputs that appear in the joyports may be powered from an internal supply which goes to logic, so overloading them may drag down the power supply to some function required to keep the OI working.



Note: the joypots don't go to ground, so their current varies as they charge a cap, and there is another resistor to limit the current when the pot is at minimum resitance.

[EricS-Team180]

Hey thanks everyone!

This is just what I was looking for.

Over the last several years we have interpreted the rules to mean ...not just that you can't pull power from the OI... but that you can't use an external power source - even batteries.

Obviously we've been overly constraining ourselves.

Thank you for your input
Eric Schreffler