We are a little confused as to which circuit breakers we are supposed to use for the digital sidecar and the analog breakout. The rules tell us that we need to use 22 AWG wire, but doesn’t say anything about what type of curcuit breaker we should use. We checked on-line, and the max load for 22 AWG wire is 7 amps. According to the wiring diagram, we are supposed to put the wires on the “max 30” amp curcuit breakers. But we found another wiring diagram (In Part 3 of the Controls System Manual) that says we should use a 5 amp circuit breaker. The problem is that this diagram comes with a disclamer “This Diagram may not comply with all FIRST rules.” Can someone please help us?
Yes, the document does imply a 22awg wire. But even in the image shown in 3.1.3, they use a 20amp self resetting breaker.
So overall, use a 20amp self resetting breaker provided in the kit. Do not use a standard 5amp breaker. The 20amp breaker is the legal breaker used for this.
Don’t confuse the control system manual with the rules. The control system manual tells you how things can be connected and used, the rules (specifically section 8) tell you how things must be connected for FRC.
<R46C> says that the digital sidecar must be protected by a 20amp breaker. <R47C> says that everything protected by a 20amp breaker must use 18awg wire or larger.
If you were doing this for fun, you could use a 5amp breaker and 22awg wire safely. As you pointed out, it isn’t safe to use a 20amp breaker and 22awg wire.
Joe is correct, look at the rulebook first. especially the sections he has quoted above. It is a good idea for your electrical person to print off the few pages with wire gauges and breaker requirements and keep them at his workstation while wiring.
Thanks everyone! We are about to wire up the board with the 20 AMP circuit breakers and get some more 18 AWG wire. We just got a little confused with the Control Systems manual. :ahh:
I have been asking the GDC to add 5 amp circuit breakers to the rules for a few years now. That may have leaked into the Control Systems doc. For now
<R46> All active Power Distribution Board branch circuits shall be protected from overload with an appropriate value auto resetting Snap Action circuit breaker (from the KOP or identical equivalent).
A. Each speed controller branch circuit must be protected by one and only one 20-amp, 30-amp, or 40-amp circuit breaker on the Power Distribution Board. No other electrical load can be connected to the breaker supplying this circuit.
And…
<R47> All active Power Distribution Board branch circuits shall be wired with appropriately sized wire:
A. 12 AWG (2.052mm) or larger diameter wire must be used for all circuits protected by a 40A circuit breaker.
B. 14 AWG (1.628mm) or larger diameter wire must be used for all circuits protected by a 30A circuit breaker.
C. 18 AWG (1.024mm) or larger diameter wire must be used for all circuits protected by a 20A circuit breaker.
D. 20 AWG (0.8128mm) or larger diameter wire must be used for the power connection between the Power Distribution Board and the cRIO-FRC .
E. 20 AWG (0.8128mm) or larger diameter wire must be used for the power connection between the Power Distribution Board and the Linksys Wireless Bridge
F. 20 AWG (0.8128mm) or larger diameter wire must be used for the power connections between the Power Distribution Board and the Analog Breakouts and/or Solenoid Breakout if individual power feeds are used. 18 AWG or larger diameter wire must be used if a common power feed is used for multiple breakouts.
G. 24 AWG (0.5106mm) or larger diameter wire must be used for providing power to pneumatic valves.
Not to confuse you even more, the rules on the breaker size relates to the wire each breaker is feeding. The breaker is a safety to prevent the wires from burning up not to protect the motors. CIM motors will still draw 129 amps at stall no matter the size of the breaker you install.
It may also be helpful for rookies to know that these breakers are thermally sensitive. They will allow current draws in excess of their rating before over heating and tripping. The higher the current draw the faster they will trip, but there is still a finite reaction time. The point is, they are only there to protect the wiring, which can handle brief current excesses, not components, which sometimes can’t survive that. Fisher-Price motors have a wonderful ability to fry before the breakers will trip.
When they do reset they are now still quite hot, and will be more apt to trip. After a couple of trips they can be considered de-rated, and should be replaced.
If you want to just protect your circuitry, like you should, you could add a 5A inline fuse to the circuit for extra protection. Of course, use the 20A breaker as you normally would, but add the fuse for the extra protection. Refer to R46 G for my suggestion.