Tortoise and AIU with DC power supply

We're in the same boat as you  and would like an easy way to hook up a Tortoise to the AIU. Unfortunately the Tortoise has a motor that stalls out keeping pressure on the switch points  and requires  contestant voltage rather than a momentary shot of current.

MTH suggests a latching relay and the schematic is shown on their web site. With over 50 tortoise on our layout we  have no intention of hooking up 50 additional latching relays so we just gave up on the AIU (it would have been nice for the record/playback feature.)

I don't know what the answer is?

Our Tortoise control  toggles are right close to the turnouts and not on a main control panel. All with in  an arms reach.

I am aware of latching relays and wanted to avoid the extra wiring for now so I ended up ordering a second AIU and will be using the ACC ports. 

I just want to know if I can use the AIU with a DC power supply without SPDT or DPDT switches etc. 

Gregg,

What would probably work for your club layout would be the scheme that the OP is already using. It's described on page 89 of The DCS Companion 3rd Edition, as described below:

Tortoise Switch Machines 

Previously, a method was discussed for using Tortoise switch machines with latching relay-type devices between the switch machine and the AIU's SW port. The purpose of such a device was to allow a longer activation period to throw a switch using the Tortoise switch machine. A less expensive way to activate switches using Tortoise switch machines through the AIU is to use the AIU's ACC ports rather than its SW ports. 

The Tortoise motor determines in which direction to throw the switch based upon the nature of the DC voltage with which it's supplied. If it "sees" a positive (+) voltage it will throw the switch in one direction. If it "sees" a negative (-) voltage it will throw the switch in the other direction. 

A diode is a small semiconductor device, available at Radio Shack and other electronic parts suppliers, that converts AC voltage to DC voltage. Depending upon which end of the diode the AC voltage enters, either DC + or DC - voltage comes out of the other end. Using a pair of diodes, wire the Tortoise motor to an AIU ACC port as follows: 

• Connect a transformer's AC Hot terminal (10-20 volts) to the "IN" terminal of an AIU ACC port. 
• The output of this AIU ACC port is filtered by placing a pair of diodes at its "1" and "2" terminals. The preferred diode is IN4001 or equivalent (Radio Shack part #276-1653). The diodes should be connected so that their orientation is reversed end-for-end with respect to each other. 
• Since the AIU ACC port will output through the "1" terminal when the port is turned on from the DCS Remote (by pressing soft key "ON") and will output through the "2" terminal when the port is turned off from the DCS Remote (by pressing soft key "OFF"), only a positive or negative DC voltage can be output by the port at any time. 
• Since only one or the other of ports "1" and "2" will have an output DC voltage at any time, depending upon which soft key is pressed, the other ends of the two diodes can be safely connected to each other without the fear of creating a short circuit. The connected pair of diodes is now connected to one terminal of the Tortoise switch motor. 
• Connect the transformer's AC Common terminal to the other terminal of the Tortoise switch motor. 
• Program the DCS Remote for the AIU ACC port in the usual manner as described in Part IV - Accessory and Switch Track Control, 4. Operating Accessories Using DCS, Programming Accessories Into the DCS Remote, earlier in this book. 

To operate the switch track, throw the switch one way by pressing soft key "ON" and the other way by pressing soft key "OFF." 

This and a whole lot more is all in “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 OGR’s web store!

Thanks for the reply.  Looks like I'll end up doing the AC with diodes.  Just one last thing.  Circuitron recommends a 14-16V transformer to compensate for half wave DC. Which I don't fully understand but get the fact that it reduces true output when using diodes.   Will a 12V still provide a reliable switching speed?

I downloaded the DCS companion this morning but haven't gotten around to reading with the holiday and family.

Will a 12V still provide a reliable switching speed?

I have no real first-hand knowledge of using Tortoise switch motors, however, according to what I've been told, it should.

Yes good idea Barry.. We would only have to do a few main line siding  switches to make meets on our single track layout. As of now we only run in one direction..  Using  the  record playback feature  we could make meets and run in opposite direction.   Diodes are  quite a bit cheaper than latching relays.  I like the idea. Thanks.

Was able to squeeze in a trip to Radio Shack before Easter dinner today. 

Lets us know how it  goes .   I can't remember, can you name the ACC  ports , something like "north switch siding A" ?

Well wiring is completed for 10 tortoise units.   When I receive my other AIU this week the other 3 will be done.

Gregg, yes you can name the ports.  I have names such as Outside Loop, Inside Loop and Yard followed with a number that corresponds to a particular turnout.

I set the ACC ports up so that when OFF the turnout is straight and when ON it is curved.   This required swapping the wires on some switch machines for correct orientation.  My only issue now is I tried to do a scene setup with the turnouts for backing into the yard, etc.  Unlike the route setup in which you can place turnouts curved or straight as you add them, this is not the case with scene setup.  I put the turnouts in the position I wanted them in before adding but they seem to have a mind of their own when turning the scene on and off.  Best case scenario would be reversing tortoise polarity so they all throw correctly when a scene is set to ON or OFF.  Huge problem with that is my brain will get fried trying to remember what position every turnout is in when I want to throw them individually.  Like I said my brain is set to remember OFF as straight and ON and curved.

I's sure as time goes on I will slowly switch over to latching relays.  Right now the priority is getting this track work fully secured and wired so I can run my locos and start on scenery.  I'm anxious as I'm getting back into trains since my teen years.