URGENT!! Need OI power brick specs for 7AM demo tomorrow!!!
 

Crisis!! We have a demo tomorrow morning at 7:00 AM to launch a new team, and we can't find the OI power brick!

Can someone look at their OI power brick REAL QUICK, and read the label for me??? I need:

1) The voltage (I assume its 12VDC, but I wish to verify it, as there may be regulators on the OI)
2) The maximum current it supplies (in mA)
3) THE POLARITY OF THE PLUG (VERY important!)

I have some power bricks here (including some 12V), and a matching plug and wiring for it now (the OI takes Radio Shack's "M" plug), but I'm NOT trying it until I know the polarity FOR SURE, and the needed current. (I am NOT risking the OI!!!)

Please reply ASAP tonight if you have access to your OI power brick. You can reply here, or email me directly at:

mailto:acti@provide.net

Thanks!

- Keith

Ahhh, geez. We have like three of em sittin at school. We somehow got two different models one with an output of 12VDC the other with an output of 9VDC. Both worked just fine as I believe the OI steps down the voltage to 5V. The minimum current that you need is 300mA as I remember. Anything over that rating should work. The polarity as I remember it is the inside was positive and the outside negative. But thats like a 51% sureness.

I really wish I could help more as I know how these demo things are but I don't have the wall transformer sitting in front of me. This is only what I remember. I make no claims, warranties, nor guarentees, expressed or implied. So, don't blame me if something smells like it's burning.

Need to be sure...
 

Thanks, but I need to be SURE... Especially of the polarity! (Center positive?? Center negative??)

BTW, we have a second demo at 11 AM, and ANOTHER in the afternoon, so even if someone reads this after 7 AM EDT, PLEASE still reply!

Thanks!

- Keith

- 12 VDC output,
- 1500 mA,
- Plug tip is positive

Note: you can get a direct replacement unit for the OI power supply from Radio Shack. Part #273-1779, it usually runs about $20.

Make sure that you use a supply with AT LEAST 1500 mA capability. While a lower level supply will power the OI, the performance of the radio modem will be significantly hampered without sufficient current. We have tried using lower level (cheaper) supplies before, and every time we had disappointing results.

Good luck!

-dave

p.s. yes, I am sure. I have the unit sitting in front of me as I type this.

Real current draw under worst case conditions
 

Thanks for the comeback, Dave!

I have a lab supply that can do more than 1500ma, but it's a variable supply. I'd rather use a power brick for safety to keep a student from diddling the voltage knob on it. (I guess Duct Tape works well, though... :D )

It sounds like you've measured the current draw. If so, what's the worst case current that you've experienced?

- Keith

I haven't had a chance to actually measure the current pulled by the OI. But I know that when we tried to use a 1 Amp supply (over the years, we have lost four of our OI and RC power supplies, so we now have a lot of experience with replacements), the OI appeared to work just fine. However, the radio link with the robot was absolute crap if we were more than 10 feet away. Moving up to a 1200 mA supply extended the range to about 15 feet, but we still had lots of drop-outs. Somewhere between there and 1500 mA you cross a threshold, and at 1500 mA it works just fine.

What I learned from all this is that I want to sit down with someone who really understands RF systems, and see if we can cobble together a really cool signal amplifier that we can run off my 100 Amp supply. Then we will sit back and drive our FIRST robot from the next state... :D

-dave

And the FCC comes a knocking...
 

OK. Based on your previous post re: the wiring, I ran a test. YES, it comes up on my lab supply. Hmmm... "At rest" with the RF connected, it's running about 400ma... OK, I believe you when you say you toased a few small bricks. <shuffles through inventory & pulls out a meter to check some bricks>

Hmmm.. OK. I've got a 1500ma 12V brick here with the right connector and polarity. <verifies it on the meter, then jacks it in> Success! We're up and running! :D Thanks!

Yea right, and pull in the FCC from the next state, too when you jam the shared airspace for a few hundred miles... <chuckle>

Thanks for the help! When we get a chance (after the next contest), I'll have to set up a lab test on the new kit to see what that EWave is pulling. (THIS copy is borrowed, and will have to go back to the original team. THAT's why I wanted to be sure about the power before tried anything!)

- Keith

You can always power the OI from your robot with a tether cable if this happens again.

<SLAPS forehead> DOH!!! How silly of me! I completely forgot about that!

However, it was nice to have it running on the radio. That's a lot more interesting than a "wired" robot. It turned out their good power brick was on it's way to Texas with this year's robot for a conference, so the one I scrounged up after getting the specs from you guys sure saved the day! THANKS!

BTW, the demo went WELL. With about 2800 students passing by Team 66's robot display yesterday, we snagged a HUGE set of leads for the new team. :D (Pioneer is MI's *largest* HS...) The school's new Robotics Class came down to see it. Team 66 even excused two drivers from classes to drive 20 miles to be at Pioneer at lunchtime to run the robot. It ran by the main cafeteria so most of the students had a chance to see it work. It made a BIG hit.

KUDOS GO TO GM/WILLOW RUN HS TEAM 66 FOR THE LOAN OF THEIR ROBOT AND PROVIDING DRIVERS!!! :D They sure get MY vote for Chairman's Award this year! This is the *second* AA team they've come all the way out to bootstrap! Those guys are GREAT! They even sent out their "FIRST Champion" banner & some photo montage boards. What a team! Go Penguins!

Thanks again to everyone here for all of your help.

- Keith