powering Banebots RS395
 

This is more out of curiosity than practicality.

We have an RS395 motor from Banebots this year. It's tiny. It draws 0.5A no-load, and 15A stalled. At peak power it's about 1/10 of a CIM.

So the question is, how do you power it?
If you use a Spike Relay, you can us a 5A fuse to keep the motor from burning out.

What if you use a Victor or a Jaguar? Then your protection is none whatsoever.

It seems that we don't have a variable-speed controller SMALL enough for this motor. I suppose if we could put ATC fuses in the PD board (and I mean FUSES, not auto-resetting breakers), then we could adequately protect it.


What would it be good for in the first place?

Re: powering Banebots RS395
 

What rule makes you think this is legal?

Re: powering Banebots RS395
 

<R48> All electrical loads (motors, actuators, compressors) must be supplied by an approved power regulating device (speed controller, relay module, or Digital Sidecar PWM port) that is controlled by the cRIO-FRC on the ROBOT.
A. Each CIM motor and Fisher-Price motor must be connected to one and only one approved speed controller. These motors must not be connected to relay modules.
D. Each other electrical load (motor or actuator) must be supplied by one and only one approved speed controller, or one and only one relay module.

Only CIMs and FPs have to have a speed controller. All other motors (i.e. RS-395) can be controlled by a relay.

<R39> All active PD Board branch circuits shall be protected from overload with an appropriate value auto resetting Snap Action circuit breaker (from the KOP or identical equivalent).
B. Each relay module branch circuit must be protected with one and only one 20-amp circuit breaker on the PD Board. No other electrical load can be connected to the breaker supplying this circuit.


This does say that each relay must have a 20A breaker on the PD, but nothing about on the relay itself.

Re: powering Banebots RS395
 

Marshall,

Keep in mind that the fuses used are sized to protect the wiring more than they are the motor. You can easily cook an FP or RS540 using allowable wiring setups.

The best way to protect any KOP motor from heat damage is to avoid stalling it.

Re: powering Banebots RS395
 

If connected to a Jaguar on a canbus network I believe it is possible to use the Jag's built in current sensing ability to limit output in real time. The software implementation might be a little hairy, as in currently non-existent, but probably doable. Take that with a grain of salt, because I've never seen it done and what you should be able to do with Jaguars and what you can do are sometimes different. Or it's just not documented.

Alternatively, stand alone current sensors could be used to provide feedback to the control system. The control system could then limit output of a Victor (or Jaguar I suppose) or turn off a relay to protect a motor once a predefined current limit has been passed.

All in all, the breakers and fuses are there to protect the wiring, not the motors. It's best practice to protect motors through mechanical, or controls methods.

Re: powering Banebots RS395
 

my advice, don't use the 395. IMO it would be better to use a larger bane bots just because it is harder to fry.

Re: powering Banebots RS395
 

Marshall,
The best answer comes with another question. Do you need to change speed or are you happy with just changing direction? The 395 is not required to have a speed controller but can be driven by one if you wish.

Re: powering Banebots RS395
 

Okay, that's a good overview.


What would an RS 395 be useful for?

Re: powering Banebots RS395
 

You don't have to use it. Might be useful for part of your minibot deployment device.

Re: powering Banebots RS395
 

I suppose that's possible. Would you use it for a trigger mechanism in lieu of a servo greater than 4 Watts?

Re: powering Banebots RS395
 

I was thinking ramp or slide but a trigger would also work I suppose.

Re: powering Banebots RS395
 

Don't forget <R55>

Unlike previous years, this year there is a mechanism to use other speed controllers. See <R48> and the blue box underneath it, as added by team update 6.

Re: powering Banebots RS395
 

Yeah, I noticed that exception. I don't suppose FIRST would approve a schematic.

Joe, by that logic FIRST would not permit replacing blown fuse. Auto-resetting breakers provide a different degree of protection than fuses, and so it makes sense to restrict that replacement, for a limited application where it is necessary. I see nowhere that it is their intent to prevent a smaller fuse being used. (They allow 12 gauge wire to be used with a 20A breaker, though you are only REQUIRED to use 18 gauge or larger.)

Re: powering Banebots RS395
 

Marshall,
Either the Jaguar or Victor can be used with this motor if you need variable speed. If you choose to feed the speed controller with #18 wire, then you can use a 20 amp breaker in the PD. At the low currents of this motor, I don't think the current sense on a Jaguar will give the accuracy you want through a CAN buss connection.
<R40> All active PD Board branch circuits shall be wired with appropriately sized wire:
Application Minimum wire size
40A circuit 12 AWG (2.052mm)
30A circuit 14 AWG (1.628mm)
20A circuit 18 AWG (1.024mm)

Re: powering Banebots RS395
 

I'm curious Al- what are the limitations of the Jaguars current sensing ability? I'm vaguely acquainted with standalone Hall effect current sensor IC's, and I know they can be fairly sensitive and have wicked fast response times. Do the Jaguars use something different or just operate on a different scale then the tiny applications I'm accustomed to?