I was reading this thread and was wondering if anyone has ever measured the current draw of the IFI Operator Interface? The AC adapter can deliver 1500 mA max, but I’m interested in the average draw. It will vary depending on how many joysticks are hooked up; a ball-park number is all I need.
I’m at robotics right now and just checked it on our 08’ controller. It was pulling 1/20th of an AMP (0.05) average. I’m sure it could fluctuate a little depending on how many potentiometers and LED’s you have attached, but not that much.
Thanks!
Ryan,
Were you measuring that number with the OI on the power supply, radio connected on OI and Robot and generally everything working? I can’t imagine even our dinky short range radio modems drawing less than 50 mA when transmitting. And it should be transmitting almost constantly while the robot is running, provided you’re talking over radio and not tether. So really, I was expecting at least 200 mA or so while everything’s running.
Also, how did you measure the current anyways? I mean… I’d willingly cut and strip one of the power supply leads to discover this, but only because we’ve got half a dozen now and really need less of them at this point.
EDIT: Per Joe below, my expectations above are that you’re measuring on the output (9V) side of the power supply.
Is that on the AC side, or the output of the power supply? I’m assuming it’s probably the input, so that would be 6W input. If we assume 50% efficiency (no idea how accurate that is), you’d have 330ma 9vdc.
That was on the DC side with everything connected. It may be the meter though… I don’t like the ones at the school. But I can take a picture if you like…
I measured it very carefully too (Going to Kevin). It wasn’t the most ideal solution, but something quick, easy, and cheap. I stuck the probe of the multimeter into the center hole of the adapter (don’t take that the wrong way either :P). Then I used some wire that was around the classroom and hooked it straight from the outside of the adapter plug and touched the exposed metal on the OI end. I touched the other probe to the back of the plug on the OI. Hopefully that all makes sense.
Again, I believe the meter is giving bad readings (it’s some off brand one that the state gives the school for their techapp classes.)
I’m going to bring my trusty old RadioShack multimeter tomorrow to see what the actual consumption is. 50mA does seem very little now that I really think of it. Considering that the LEDs alone pull probably 5mA or more each, and there being like 20 of them… then the radio, and the CPU, the joysticks, and everything else.
Well I rechecked it with my RadioShack multimeter and it said .001AMP… so I know that’s not right. Then I checked it with my Craftsman multimeter and had a more likable reading. Here is what it said: -0.41AMP.
That sounds like a much more realistic reading. Hopefully dyanoshak is still keeping up with this thread, as an order of magnitude difference might be a bit important to his plans. Kind of the difference between getting 3 hours of run time out of a dinky 9.6V 200 mAh NiMH vs. less than 20 minutes.
Given your readings, I’d probably budget for the OI drawing 1A if I had the space and weight in my project to be that conservative. Otherwise, I’d budget for 500mA just to give myself a little wiggle room in case you’re still a bit off.
I have been keeping up. 50 mA seemed low to me too; I was going to split the difference. Thanks to everyone for your measurements. 
I wanted a ball-park number so I could pick out a reasonably priced NiMH battery to use during demos.
I would also look into getting a higher voltage battery and a voltage regulator to step it down. Analog values have been goofy with me before while using two nine volt batteries in parallel. I hope you have better luck than I did.
Even though the AC adapter provides 9V, our team has used 12V batteries without any issues before (without a 9V regulator).
On a side note, using a battery to power the OI will void the warranty, but it is definitely nice not to have to plug in the OI all the time while testing the robot and getting everything working at a demo.
I mean, what does not void the IFI warranty…
I believe a few years ago the controllers had 12V adapters, then last year they moved to 9V ones, but don’t quote me on it.