Wiring lionel switches to aiu

[Anonymous]

I am using track power for the switches and I have them wired to MTHs aiu. I would like to use separate power for the switches and need to know if I have to wire the switches to the aiu differently?

[AlanRail]

No

if I understand your question correctly; Typically, the AIU provides ground to the switches; Power the switch any way you want so long as the ground that is connected to the AIU is also connected to the ground of the power source for the switch ( mutiple power sources if used, each must have matched polarity)

Alan

[daan]

If polarity isn't matched the power sinks away on your track and the safety will click in. you can measure the polarity if you have a voltmeter for AC, before connecting to anything, measure between the earth connections on both transformers, it should have a zero reading. Also the field connections should be measured, should also have a zero outcome (or an outcome of the difference in voltages. P.e. trafo1 20 volts ac, trafo 2 15volts ac, earth should measure 0, field should measure 5 volts.)
best is to power the switches from a light output from the trafo you use for the trains.

[Anonymous]

The AIU should be, as stated above, set up so that when its relays close, the closure is on the common (ground) side of the circuit. This is the same way that the non-derailing feature of the Lionel switches work. This is also the way that the regular switch controllers work.

I think what Daan is saying is to make sure, when using an external power supply, that the transformer for the track and the transformer for the switches is properly phased.

By the way, it is highly desireable to use the external power supply with DCS anyway, as the switch machines occasionally interfere with the DCS signal. This is an issue with the 027 switches, as they are track powered only (unless one modifies them).

[lionelsoni]

Why would the switch supply voltage have to be in phase with the track voltage? It doesn't even have to be AC.

[AlanRail]

The term "in phase" is a bit confusing, that's why I stated the "in phase" condition as instead matched polarity of the AC house voltage.

If the grounds( or power souces) are separate then by all means as lionelsoni says you dont need to "phase" the transformers as they would not be connected.

threerailguy's question was not clear in that I took the situtation where he was trying to minimize changes to the wiring to the AIU and the switches. In that case just connect the new power source directly to the switches and after phasing connect the ground of the new power source to the ground line of the track power source;

If the new power source for the switches is not the same type (AC or DC) as the track power source then of course you cannot phase an DC power source for the switches with a AC power souce for the track.

In THAT case you need to remove the old ground line coming into the AIU and replace it with the Switch power source ground as well as the power line coming into the switch.

Alan

[lionelsoni]

I'm actually not familiar with this AIU thing; but I infer from the discussion that it provides a relay contact to throw the switch. If that is correct, it is in principle no different from a traditional switch controller, which is a normally-open momentary switch.

All the switches on my layout are separately powered, from a DC supply. Most of them use the isolated running rail built into the switch or one that I isolated near the switch, to implement the non-derailing feature. The isolated rail operates the switch machine by connecting the isolated rail to the other running rail, which in turn is connected to the common return ("ground") for the track voltage and for the DC switch-throwing supply.

This all works fine; and I see no reason why it should not, since there is no interaction between the two power supplies. If my assumption about the AIU's providing relay contacts is wrong, then, as Emily Litella would say, never mind.