How many 393s do you (tentatively) plan to use?

Well, the new no-restriction rule (or lack thereof) should be interesing. What does everyone plan to do?

why use less than the limit?
if you say “you’ll trip it”, then you are doing it wrong…

This is going on my favorite quote. Just sayin’

Also Im using 12. :stuck_out_tongue:

  • Andrew

Haha yeah, Our team talked to an intelitek engineer on saturday for about an hour, and learned all about “tripping” Otherwise, we would have just slapped another battery on there and said problem solved!

Sorry, not enough options:p
@murdomeek- i just lOoked and realized i wrote 8, i meant to press 9-10 cause thats what both my robots will have

I plan to use 12 :slight_smile:

Same here. Using 12 :slight_smile:

Are you planning to join the college competition, or were you just joking?

We’d definitely like to see more teams in the college competition.

It really depends on the outcome of my designs.

I will be using HS motors for the drive, and lift. Other than that, I will have to wait.

I’m planning on doing the college competition if we can get the funds together.

I like the comment but it all depends on the robot’s build too. If there’s going to be a bot going nuts with 393’s and has a lot of junk on it, cortexs will be shot, motors fried, batteries drained constantly. One of the tech guys at worlds told me my drive died because all four motors were on the power expander. It was a possibility but honestly that was a bunch of bull because it worked everywhere else, and the field tiles had as much friction as duct tape has. Our 1200a team had a dent in their field even and they shot all of their motors because they kept getting stuck on their chassis.

I plan to use 8 next year but hopefully not I’d hope to only use 6, if not, oh well. :slight_smile:

I definately Think that 6 is a good number. I will ave to do some tests, but i think any more than that will pull to many currents

and there’s always this option called don’t set all of your motors at 100% all at once…
i prefer using 10 393s but be scaling motor power accordingly

running 4 on the lift and 4 on the drive would be bad.

6 Is it for me as well as my team.

I hate to say it but the man you talked to was correct. There really should only be 2 high strength motors to any particular breaker in the cortex/power expander. That is why I would recommend only using 6 high strength next year because you can have them all spread out accross the breakers.

My team is also thinking of using 6 high-strengths. We have had our fair share of experience with tripping breakers, even with just 4 high-strengths spread out equally over the cortex and power expander. Ideally, our final robot shouldn’t have troubles with drawing too much power.

I like the idea of managing how much power is sent to your 393s when using 9 or 10, but we still need to see if it’s reasonable for our design.

if they have “a lot of junk” on their robot, they are “doing it wrong”
we have always have had 4 HS motors on drive at 1.6:1 ratio, never tripped in a competition once

by analyzing what you said above, you are:
driving too much weight “doing it wrong”
driving too fast “doing it wrong”
maybe too much friction in the drive “doing it wrong”
you are pushing DEFINITELY “doing it wrong”
mats has too much friction; your motors are on the verge of tripping on normal mats so when you drive on “new” mats, you trip “doing it wrong”

as you can see, there ARE many ways that using 10 HS motors can go incredibly wrong (worse than 4 HS problems listed above)

however; all those problems can be fixed if you “do it right”

so im still sticking with 10 HS motors :slight_smile:
(12 for college)

12, if it does in fact work

I actually don’t know for certain what makes the breakers trip on the cortex/power expanders. For example, if you have 12 HS motors, split into 4 per breaker, and ran them all with no load but full speed, would that cause problems? Would running one/two/three/etc HS motors at stalling loads be any different? If they’re limited by the amount of current the draw at any given point, and that limit won’t accommodate the number of HS + regular motors that you run at any given time, then there’s not much point, right? Still, if you, for example, had 6 HS on drive and 6 on the lift and misc. systems, and it could only handle running 6 motors at a time, then you could have them all HS, but only exclusively drive or lift.

If someone could post a tl;dr technical explanation, that’d be pretty helpful.

Our team has always had all four 393 strapped on to one power expander, we’ve never had any difficulties with this.

I thought I gave a pretty reasonable explanation yesterday in this thread.

Here are some simple rules to go by

cortex + power expander, maximum sustained current is 12A for about 30-60 seconds.

1 393 motor working at half of stall current = 1.8A.

12 / 1.8 = 6 2/3 motors

After this it gets tricky, the cortex can sustain higher current for short periods so it’s possible the all 10 motors could run for perhaps 10 seconds without causing the PTC’s to trip. Our normal drive with 2 x 269 and 2 x 393 will draw over 10A when these 4 motors stall, (2 x 2.6A + 2 x 3.6A = 12.4A), but we rarely trip any breakers as it only lasts for a second or two before power is removed by the driver.