# Talk to me about new locos and ZW (or other old) transformers



## Nathan Plemons (Jun 24, 2011)

A few weeks back I was at a train shop and the gentleman had a very nice looking MTH locomotive with all the fancy new bells and whistles. I asked the gentleman if I could even run such a locomotive with just my old ZW transformer or if I would need a whole new type of system.

The man was very nice and told me that I could in fact run new locomotives on a ZW, just with limited features. This makes sense to me as the ZW has no way to trigger all the new sounds, etc. He also recommended that I buy (which he had in stock) an instant trip circuit breaker to protect the electronics in the new locomotives in case of a derailment. He claimed that the breaker in the ZW is designed to protect the transformer, not the train. Again this makes sense as I know for a fact that the circuit breaker on the ZW can be fairly slow to respond.

So, for the questions:

1. Can anybody verify that what he told me is correct? Can I indeed run a new protosound (1/2) or lionel legacy, or any other style new locomotive off of my ZW? 

2. If yes, what features will I have? Obviously I couldn't control everything, but would the ZW whistle and direction controls still work?

Thanks a bunch!


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## gunrunnerjohn (Nov 10, 2010)

Yes, you can indeed, I've done it here. You can "roll your own" bell button with some diodes and a push-button in a small box, and you already have a whistle button.

Note that for PS/2 or TMCC/Legacy locomotives, having either the MTH DCS or Lionel TMCC or Legacy systems are obviously necessary to realize the full scope of capabilities of the locomotives.

It's actually not that expensive to get into TMCC, I picked up two sets of CAB-1/Command Base combinations for Lionel for just over $100 on eBay, you just have to setup a search and wait for them to come by. The Legacy controller of the setup for MTH DCS will set you back around $300 nowadays.

To recap, you can do basic train operations, operate the whistle and bell, etc. However, you won't be able to use the electrocouplers on PS/2 or TMCC/Legacy locomotives without the proper control system.


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## Nathan Plemons (Jun 24, 2011)

My layout isn't really advanced enough to need any of the other stuff anyway. I would just hate to spend money on a locomotive only to not be able to use it at all.


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## gunrunnerjohn (Nov 10, 2010)

Here's a simple Whistle/Bell controller that I built to use for a conventional train, you just connect it between the track and the transformer. One button is for the whistle, the other for the bell. All it consists of is some diodes, push buttons, and terminal connections.


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## Nathan Plemons (Jun 24, 2011)

Certainly looks simple enough. If I end up with one of these loco's I'll give it a shot. A few weeks ago he had a 2-6-6-6 and he only wanted $300 for it.


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## gunrunnerjohn (Nov 10, 2010)

You don't need that much complexity to run TMCC/Legacy, here's my test track, there are currently four locomotives that can be independently run. I'm working out the issues with locomotives, switches, and TMCC controls. I keep changing this to work on other pieces.


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## Nathan Plemons (Jun 24, 2011)

Let me make sure I understand your wiring correctly on that control box.

It looks like you have 10 diodes, 5 facing either way. When no buttons are pressed, the current will flow across all 10 diodes. It looks like when you press either button it bypasses 4 of the 5 diodes on either side. This in effect would create a DC bias, either positive or negative on the rail to operate the control.

If that's how it works, that's all well and good, I just have one question. Does this not effectively lower the total voltage to your track just by having it connected? I'm concerned because I basically just used the exact same trick to lower the voltage to the motor on my Berhsire while keeping the light and smoke unit at a higher voltage. I'm afraid that if I introduced this box as well, that I would lower the voltage too far for that locomotive to run.

I did have another thought, however, tell me why this wouldn't work:

Currently on my ZW I have terminals BU running direct power to my switches and DU providing power to my track. This leaves AU and CU disconnected. I'm thinking though that if I connected AU through the horn / whistle box and also connected it to the track that I could effectively use the DU handle when running my Berkshire and use the AU handle for any newer locomotives. In theory anyway it seems like it should work. The million dollar question, however, becomes as follows... What happens if I accidentally engage both handles at the same time? I wouldn't intentionally do this but sometimes the controls might get bumped. Would it harm the transformer / train?


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## gunrunnerjohn (Nov 10, 2010)

You understand the box just fine. I guess the real question is, when you're running the Berkshire at maximum speed, are you at full throttle on the ZW?

Another way to simply solve the voltage drop issue is to put a DPST switch across each row of diodes, you can throw it one way to bypass all the diodes and run voltage directly through the box, and the other way to have horn/bell functionality.

Don't connect multiple outputs to the track, that's a real bad idea!


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## tjcruiser (Jan 10, 2010)

John,

Refresh my memory, because I'm not sure I understand you simple circuit, even with Nathan's good description.

In my simple-mind terms ...

A whistle controller works by sending a DC signal out over the normal AC track voltage, right?

How does a bell control work? Is it simply a question of polarity? + DC for whistle, - DC for bell? (Or other way around, maybe???)

If I recall from earlier dialog here, old-school whistle controllers kick out around 3V DC initially to trip the solenoid, with a quick drop to around 1V DC to hold it in place while the button is pressed. Is the same magnitude of voltages used for bells (albeit with the opposite polarity???)

What's the difference between your yellow button and your green button? Looks like one is simple on/off, whereas the other is more complex (judging by the pinouts on the back)???

Set me straight ...

TJ


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## Badwolf & Arizona RR (Jun 17, 2011)

Based on the above, it sounds as if $300 for an MTH DCC system would be easier to master.


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## gunrunnerjohn (Nov 10, 2010)

Badwolf & Arizona RR said:


> Based on the above, it sounds as if $300 for an MTH DCC system would be easier to master.


You give up too easy. 



TJ, the bell is just the opposite polarity DC bias on the track.

The circuit simply drops a few volts through the diodes, having an even number on each side keeps the DC bias to zero until you push the button. When you push one of the buttons, it removes most of the diodes from one side of the set and injects a DC bias onto the track. Doing the same thing on the other diode string injects the opposite DC bias onto the track.


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## Badwolf & Arizona RR (Jun 17, 2011)

I used to know all this stuff back in high school (took a pre-engineering curriculum), but seem to have misplaced it. I do know more about cars and music now, so there has been a trade off.


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## tjcruiser (Jan 10, 2010)

gunrunnerjohn said:


> TJ, the bell is just the opposite polarity DC bias on the track.
> 
> The circuit simply drops a few volts through the diodes, having an even number on each side keeps the DC bias to zero until you push the button. When you push one of the buttons, it removes most of the diodes from one side of the set and injects a DC bias onto the track. Doing the same thing on the other diode string injects the opposite DC bias onto the track.


OK ... I mostly understand. What is the last pair of diodes doing for you, then? Isn't that pair dropping track voltage regardless of which buttons are pushed?

And, just so that my brain doesn't hurt too much ... I recall that the old-school Lionel whistle controllers (like a 167) had a shunt circuit that would "burn off" voltage (through heat) until the button was pressed ... such that the net AC voltage to the loco remained more-or-less the same regardless of whether a DC signal was being sent to the whistle. I.e., constant speed of the loco. Am I correct that your circuit doesn't have the effect of a shunt circuit?

Thanks for you patience in stepping me through this.

TJ


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## gunrunnerjohn (Nov 10, 2010)

The last pair of diodes are necessary to isolate the strings. If you shorted all the diodes, you're remove both strings from the picture, thereby totally removing any DC bias.

I also realized when thinking of bypassing them that you only need a SPST switch, you just want to short all the diodes for a pass-through.


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## tjcruiser (Jan 10, 2010)

Thanks. Clever.

For future search hits:

custom whistle controller
custom bell controller
diode whistle controller
diode bell controller


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## gunrunnerjohn (Nov 10, 2010)

I added a couple to the tags.


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## plandis (Oct 5, 2011)

yes. a small DC voltage superimposed on the AC track voltage. think if it as moving the "zero crassong" point of the sine wave up a few volts or down (reverse polarity) to pull in the solenoid. bell for one polarity, whistle for other. each diode prepresents about .07 volts forward biassed. two diodes would be about 1.4. so 4 doides would give you about 3 volts. offsetting that zero crossing point by 3 volts.


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## gunrunnerjohn (Nov 10, 2010)

Actually, each diode represents about .7, not .07.


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## plandis (Oct 5, 2011)

you are absolutely right!! my fingers were supposed to type 0.7!! well- that is for selenium doped diodes that is!!


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## gunrunnerjohn (Nov 10, 2010)

Well, somehow you managed to add .07 to .07 and come up with 1.4, I was going to call you on that one too.


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## plandis (Oct 5, 2011)

you got the jist!!


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