Out of 40amp slots

[Brandon_L]

So I've run into quite a funky problem that I've never seen before. Heres a list of motors and what their used for on our robot:

2 Banebots (conveyor)
2 FP (shooter)
4 CIMs (drive)

4+4=8, the exact number of the 40amp slots on the P/D board.

Problem is, were missing our bridge manipulator which is most likely two window motors. And I'd like to put those in the 40amp, as they need the power. Would anyone recommend putting a victor/jag into a 30amp for something like a conveyor belt?? It seems like it should be fine, but I thought I'd check.

[Mr V]

The circuit breaker does not define how much power the device uses, it only limits the maximum that can flow through the circuit to protect the wiring. I've never seen any window motors that need more than 30 amps in their native environment so they should be fine on a 30 amp breaker.

[Isaac501]

Check motor curves, determine expected load and design around them.

You're doing it wrong.

[Al Skierkiewicz]

Brandon,
The window motors actually draw about 20 amps at stall. (one slightly higher and the other slightly lower.) Collin you were looking at max power not current I think.
It is important to remind everyone that with increased motor usage, available electrical power from the battery will become an issue. You cannot simply run all the motors at the same time. The terminal voltage on the battery will fall to the point that the Crio either disables all outputs or it reboots. Be careful to watch terminal voltage as displayed on your dashboard while practicing. Expect that transients are much worse than what is displayed on the dashboard.

[MrForbes]

We're only using 4 of the 40 amp breakers....we're running our shooter and harvester FP motors on 20 amp breakers. It seems to work just fine, too.

[bladetech932]

we have never used the 40 amp breakers for anything except Cims also we usually use 30s for window and 20s for Banebots.

[Akash Rastogi]

Originally Posted by squirrel

We're only using 4 of the 40 amp breakers....we're running our shooter and harvester FP motors on 20 amp breakers. It seems to work just fine, too.

Can you post up if you have any issues with the shooter FP motors on 20 amps? I'm just curious.

[MrForbes]

Originally Posted by Akash Rastogi

Can you post up if you have any issues with the shooter FP motors on 20 amps? I'm just curious.

I don't know for sure....you see, we have software controlling it, and the software is not bulletproof. Thinking back, we might have had the breaker snap off a couple times when the software was not working properly (ie motor running backwards, ball was forced into shooter wheel, strange things happened but no motor smoke)

We also designed our robot to use the FP motors in the sweet spot, somewhere around 80% of no-load speed. And we run 18 guage wire to them because it's easier to deal with, and use 20 amp breakers, and we really don't want to be able to give them any more current than that, since they have a way of making smoke when you do.

[Trez]

Originally Posted by Al Skierkiewicz

Brandon,
The window motors actually draw about 20 amps at stall. (one slightly higher and the other slightly lower.) Collin you were looking at max power not current I think.
It is important to remind everyone that with increased motor usage, available electrical power from the battery will become an issue. You cannot simply run all the motors at the same time. The terminal voltage on the battery will fall to the point that the Crio either disables all outputs or it reboots. Be careful to watch terminal voltage as displayed on your dashboard while practicing. Expect that transients are much worse than what is displayed on the dashboard.

What is usually the bear minimum volatge that the cRIO or the wireless router starts to reset? Is it like 10 volts?

[slijin]

Originally Posted by Trez

What is usually the bear minimum volatge that the cRIO or the wireless router starts to reset? Is it like 10 volts?

It's well below that. The reason teams are required to wire the cRIO and the bridge into the dedicated power terminals at the end of the PDB isn't because FIRST likes to make random rules. These power terminals have been designed so that your cRIO and bridge will continue functioning well after the rest of the robot is starved for power.

The cRIO-II operates down to 9V although its nominal power supply on the PDB is 24V. The original cRIO operated down to 19V, and would cut out when battery voltage dipped to 8V.

[cgmv123]

Originally Posted by Trez

What is usually the bear minimum volatge that the cRIO or the wireless router starts to reset? Is it like 10 volts?

The wireless router and the cRIO supply both have boosters designed to ensure no loss of connectivity. The supplies stop working at about 5 volts, based on what others have said. I don't know the actual specifics for the D-Link, but the 8 slot cRIO needs 19 volts to function and the 4 slot cRIO needs 9 volts to function.

[Al Skierkiewicz]

Originally Posted by Trez

What is usually the bear minimum volatge that the cRIO or the wireless router starts to reset? Is it like 10 volts?

Trez,
The power supplies in the PD which feed the Crio, the Wireless Bridge and the camera drop out at ~4.5 volts at the battery input to the PD. The Crio is programmed to disable all outputs at 5.5 volts in order to try to protect itself from reboot. Heavy motor use will pull the battery down to these critical levels for short periods of time without causing any problems, but a robot that is not designed with efficiency in mind, will cause some or all of these items to fail without warning.
A Crio disable is pretty obvious with a sudden jerky movement or response under driver control. If the battery goes down to less than 4.5 volts for more than a moment, the Crio and/or wireless bridge and/or camera will reboot. The Crio can take anywhere from 20-60 seconds to reboot depending on your software. The wireless bridge can take up to 50 seconds or more to reboot and reconnect to both FMS and the Crio. The power supplies will restart very quickly when the battery returns to more than 5-6 volts.
Please remember, the battery has some internal resistance, your wiring has some resistance, the circuit breakers have some resistance. When you pull a lot of current from the battery, the current passing through all this resistance will drop the voltage available to critical items like the Crio and wireless bridge power supplies. #6 wire has ~0.0005 ohms per foot and the battery has 0.011 ohms at full charge and room temperature. An average robot with 4' (both red and black musst be considered) of #6 with four CIMs in stall while pushing another robot will drop a minimum of ~5.2 volts in the resistance in just those components taking the available voltage to 6.8 volts at full charge.

[Mr. Lim]

I second moving the Window Motors to a 20A or 30A amp breaker. You'd have to try really darn hard to get more than 20A out of those.

You are using your FPs for your shooter, which is a free-spinning mechanism. That means it will likely only operate in the low-current regions of your torque curve. That also means it is certainly possible to put them on a smaller breaker, if you are very sure there is no chance of stalling your shooter (i.e. stuck ball).

[wireties]

All 4 of our shooter motors are on 20A breakers, no problems so far. Of course we are running them in a "sweet spot" on their power curve, they are not getting the slightest but warm.

HTH

[thefro526]

Originally Posted by Al Skierkiewicz

Brandon,
The window motors actually draw about 20 amps at stall. (one slightly higher and the other slightly lower.)

Quoted this just so it's read again.

There's no reason to run the windows on anything but a 20A breaker.