COULD SOMEONE EXPLAIN WHAT HAPPENS WHEN YOU PUSH THE WHISTLE BUTTON on a ZW or

[Anonymous]

any transformer that makes the whistle operate. I don't grasp the concept of what energy triggers the motor in the tender to cause the whistle to blow and how does that signal coexist with the track voltage. Thanks to any who responds.

[pbjwilson]

When you push the button on the transformer a little jolt of electricity wakes up the engineer in your engine and he blows the whistle. Thats the way it works on my layout anyway.

Some of the techies will give you some technical mumbo jumbo, but dont you believe it.

[chuck]

There is a special relay in the tender that responds only to a DC spike that is superimposed on the track voltage.  The relays can be made to be polarity sensitive so a positive DC spike can trigger one action and a negative spike another (e.g. horn/whistle for one and bell or the other).

[mitchelr]

I'll try.... The transformer runs trains on AC, the whistle button lays  DC voltage on top of the AC "locomotive power" that runs the whistle.

Not sure if that explanation is clear but someone else will come along with a better explanation.


Mitch

[1688torpedo]

Hello Arnie!    The simple answer to your question is that when you press the Whistle Button on your Transformer a Rectifier is activated that superimposes a DC Signal over the AC Current flowing through the rails which in turn activates the Relay in the Whistle that in turn activates the Whistle Motor (or computer chip for a Electronic Whistle) & this is how a Whistle works. Bob(Lionelsoni) is a electronics genius & will most likely offer some more info for you as well. Hope this helps. Take Care.

[ben10ben]

To add a little bit more to the accurate answers you have all ready received, three things happen when you push the whistle button.

First of all, a rectifier is switched into the circuit. This imposes a DC offset of aproximately 5 volts onto the sine wave, which activates the relay in the tender.

Second, as you continue to push the lever, a Nichrome resistor is switched in parallel with the rectifier. This reduces the DC offset to aproximately .8 volts, which is enough to hold the relay.

Finally, as you reach the end of the whistle button travel, a 5 volt winding is switched in parallel to the transformer winding, thus raising the track voltage by 5 AC volts. This is intended to compensate for the draw of the open frame motor used in postwar whistles.

[lionelsoni]

Pretty close.  But the extra 5 volts comes at the beginning, at the same time as the rectifier.  Then the rectifier is shumted by the resistor as the final step.

Some more details:  The relay doesn't care about the polarity of the superimposed DC; that's important only with electronic whistle-bell arrangements.  The relay has a copper ring at the end closest to the armature.  This acts like a shorted transformer secondary winding (the relay winding is the primary) and cancels the AC magnetic flux at that end of the relay, so it doesn't operate on AC.  However, the copper ring has no effect on the DC component of the flux; so the relay operates when DC is present.

[ADCX Rob]

.

...Finally, as you reach the end of the whistle button travel, a 5 volt winding is switched in parallel...

Should be "series"

Rob

[ben10ben]

Rob,
Of course, you're right. Putting a 5 volt winding in parallel with a winding of higher voltage would be a really bad idea.

Bob,
I was working on memory, but seem to recall that on my KW, things happened as I described. Pushing the lever slowly first caused a pretty dramatic slowdown, followed by a pick up in speed, and then the tell-tale brightening of the lights from the 5 volt winding. I could be remembering incorrectly, though. In any case, the KW whistle lever has enough resistance that it's often difficult to push it as smoothtly as one might with other transformers.

Is the KW different from the ZW with respect to how the whistle control is connected?

[ADCX Rob]

Ben,

It appears to drop first, because the rectifier is in series w/o any shunting, but this is the "pickup" DC current phase, then the shunt is cut in, with most but not all of the rectifier being cut out, or shorted/bypassed by the resistance wire, resulting in the lower "holding" DC current imposed on the wave, but higher overall voltage to the train.

It's virtually the same on all MultiControl transformers.

The old whistle controllers worked on a choke coil based system, providing almost the same result.

Rob

[Ole Timer]

 I like pbjwilson's answer better ... it made me laugh ... !