Accessory Current

Some of the early TMCC control boards were designed for 10 amps or less.  Unfortunately dead short derails tended to be more destructive.  I reduced track power with 8 amp inline fuses to protect equipment.   My power supply is a parallel set of Lionel PH135.  The parallel thermal cut-outs put power output at 15 amps, a bit much.   Cutouts/protection has gotten better over the years, but demand for more power is still there. 

Small accessories, that don't involve track power, I fuse at 3 amps or less.  

Track power fuses.  Top center of picture, (8) circuits.  (8 amp fuses)

carl552 posted:

What is the maximum accessory operating current AC or DC that I should design circuit boards for?

Thanks, Carl

I'm confused, exactly what kind of circuit boards are you designing?

I am designing a PCB board with DipTrace to control accessories with mini relays for AC and power transistors for DC current.  I want to how wide and thick I need to make the power and ground traces and how many accessories can share a power and ground on the PCB.

It seems you may be trying to re-invent the wheel:

https://www.ebay.com/sch/i.htm...y+board&_sacat=0

Pair those with some LTV-844 (AC Activated) opto-couplers, TVS Diodes, and current limiting resistors and you have magic circuitry you are seeking!

Here you go, PCB Trace Width Calculator.