MTH AIU Wiring Questions!!

Jeff,

Should I use 16 or 18 AWG wiring for switches?

18 or 20 gauge works well. It doesn't have to be stranded, either, for switch tracks.

Okay, does the AIU have to updated at all on the DCS loader program??  Or is it never needed to be updated?  Also, says I must use a separate transformer to power my switches using the AUX posts on the switches.  Can I use a 250 watt Z transformer from Lionel??  But, I know it cannot be connected to the DCS system.  But, does it have to be in phase with the transformers on the DCS system or it does not matter??  I figured one Lionel Z transformer should do the job for my 8 switches.  2 on each dial.  What should each dial be set at?  18 or 24 volts??  My manual for my switches does not say.  Thanks.

Jeff,

does the AIU have to updated at all on the DCS loader program??  Or is it never needed to be updated?

The AIU has no software to be updated. It simply is what it os.

Also, says I must use a separate transformer to power my switches using the AUX posts on the switches.  Can I use a 250 watt Z transformer from Lionel??  But, I know it cannot be connected to the DCS system.

You can use whatever you like that will get the job done.

 does it have to be in phase with the transformers on the DCS system or it does not matter??

It should be in phase with all of the other transformers on the layout for safety reasons. Further, if it's not in phase with your track power transformers, the switch's cannot be wired for automatic non-derailing operation.

This and a whole lot more is all in MTH’s “The DCS Companion 3rd Edition", available for purchase  from many fine OGR advertisers and forum sponsors, or as an eBook or a printed book at MTH's web store!

Got it!!  Thanks.

personally I don't even try anymore to use stranded wire for the AIU ports.  I did use stranded the very first year that I had one but it frustrated me enough that I now stick to solid.

I have a question regarding commons on transformers and TIUs.  Are all commons on TIUs connected together internally, and thus also all commons on transformers are connected together at the transformer internally (so all of the in and out commons of the TIU would also be connected to all the transformer commons automatically)?  I have seen references to jumpering between commons to connect them together but if they are truly common, that would be redundant.

Bob

Bob,  Obviously I am far from the expert on DCS stuff, but I do use it.  I have read, I'm PRETTY SURE, in teh past that they original TIUs ('G"???) did NOT have their commons tied together within the TIU.

I realize this isn't the answer to your question though but thought it might be useful.

- walt

You have it reversed, Walt.  The Rev G's had all commons connected in the case; later models do not, so should have an external jumper connecting all 4 commons.  No opinion on what's inside transformers, because there is such a variation.  Postwar ZW U-posts were all connected.

I took my ohmmeter to the TIU just now and found the following.  The various specific in and out commons are connected together (fixed voltage in common is connected to its associated fixed voltage out common).  The 4 commons on each side (in and out) are NOT connected together.  However, if one uses a transformer with all the commons connected together, or if one uses jumpers to connect all the commons on either the input side or the output side of the TIU together, all 8 commons will then be connected together.

The commons on the MTH Z4000 are all connected together, so that will carry on to the TIU for the associated inputs and outputs.  All 4 commons on the Lionel ZW are connected together, so if a ZW is used to power all 4 of the TIU inputs, all the TIU input and output commons will be connected together via the ZW.

If anyone disagrees with my finding, I would appreciate feedback.

This is particularly important when thinking of adding TMCC, which sends its signals through the outer rails.

Bob

If using DCS, I would still connect all 4 TIU outputs together, to avoid forcing return signals to go through the transformer coils.  Don't know if it really makes a difference---I'll let knowledgeable folk weigh in on that---but it can't hurt.

In fact, on my layout, no common is fed through the TIU; the black outputs are connected together, with a wire going to the layout ground buss that runs from transformers.  Nothing connected to TIU black inputs.  TIUs' internal power comes through AUX.

kbaybob posted:

I took my ohmmeter to the TIU just now and found the following.  The various specific in and out commons are connected together (fixed voltage in common is connected to its associated fixed voltage out common).  The 4 commons on each side (in and out) are NOT connected together.  However, if one uses a transformer with all the commons connected together, or if one uses jumpers to connect all the commons on either the input side or the output side of the TIU together, all 8 commons will then be connected together.

The commons on the MTH Z4000 are all connected together, so that will carry on to the TIU for the associated inputs and outputs.  All 4 commons on the Lionel ZW are connected together, so if a ZW is used to power all 4 of the TIU inputs, all the TIU input and output commons will be connected together via the ZW.

If anyone disagrees with my finding, I would appreciate feedback.

This is particularly important when thinking of adding TMCC, which sends its signals through the outer rails.

Bob

Hi Bob,

Your findings are correct.

Thanks for pointing out my 'backwards' answer RJR.  Darn, I was sure I had that right but obviously I trust your knowledge a lot more than mine when it comes to AIUs!

If you're trusting me & my memory, Walt, you're in deep trouble.