RELAY BOARD FOR USE WITH THE MTH AIU

The relays in the AIU are 5A relays, why do you feel they won't handle a turnout directly?

I would like something like this to turn on/off power between the track and a TPC400 with two PH180s powering it.  This could be a maximum of 20 amps, far more that the AIU or Lionel's BPC or ASC could handle.  What is in the circuits?

Ron

You can use most any relay that suits your need with the proper coil voltage. A DPDT one could switch 2 different circuits. 

Dale H

My relay board has relays rated for 40 amps. My turnouts are all powered using AUX power.

Note: MTH states that their RealTrax turnouts draw about 1.25 amperes each.

The reason I need a relay for turnout control is that I may want to operate several turnouts at the same time to set a route.  So I only need to operate 1 high current relay from my AIU SW output to select multiple turnout solenoids. Therefore I avoid any momentary high current draw from my AIU SW outputs.

Note: If I close 4 turnouts at the same time up to 5 amps would be required.

Also if a short occurs the external relay can handle a high current fault. 

I do however have individual fuses installed for each of my turnout AUX power circuits.

Whatever floats your boat.  Seems like overkill for most situations involving turnouts.  For the rare instance that I would want to switch four or more with a single control, I'd just add an aux relay. 

Another reason I use separate relays is that they are all operated by 12 volts dc. Since the relays are "DC" I can use diodes in my routing logic. For example when I want to select multiple turnouts to choose a route I can implement a "diode network" to select the route. The selected diode network then determines which relays are energized and therefore which turnouts are energized.

I also use 12 volts dc when using the AUX outputs from my AIUs. The AIU "IN" terminals are all at DC common.

Note: The 12 volt power is provided by a KW transformer and simple diode bridge. The 12 volt power is also protected by separate circuit breakers.

OK, I get your logic, but I have a question:

Why don't you just program the route into the TIU, it will throw any and all switches (wired one or one pair per AIU port) to the needed setting with no overloads.

I do it, it works VERY well. I throw up to 4 switches at once.

The only thing extra you may need is an additional AIU for more switches. I have 2 in my current layout and will be adding a third later. Cost is a bit higher than your parts list but time to assemble is minimal.

I like your solution Russell, you also don't lock yourself into hard-wired combinations.