Using a relay to operate a magnet (question)

As to activation of an electromagnet from the output of the whistle relay, sure -- wiring and voltage details aside, a relay is a relay is a relay, and anything that has compatible power requirements can be substituted for the whistle motor.

As to crafting an alternate relay, I don't see why not. Off the top of my head, I'm not sure what exact components would be needed, but something that would block the AC from the track (some choke/capacitor combo?) while allowing the DC voltage through would be needed, but I'm not sure it would be much less bulky than the Lionel unit. Those more conversant with the DC offset circuitry may have more informed opinions!

@trainman48 posted:

Hi all,

I've had a few prewar Lionel whistling tenders, and was told when the whistle button on the transformer is pressed, it sends out a DC signal through the tracks, activating the relay coil and connecting the points.  If this is true, couldn't a magnet be wired to the relay rather than the whistle motor? And further, are there any smaller relays currently on the market that operate on the same principal as the bulkier Lionel unit? This is for a special project and would appreciate any information regarding this.

The whistle relay is a special case, it is what is called a "slugged" relay, which is one which has a couple of copper disks around its pole piece.  These shield the pole piece from the fluctuating magnetic field produced in the coil by the AC voltage but do not hinder at all the steady component produced by the DC component.  This causes the relay to operate.  It connects the whistle motor to the track voltage; and the whistle blows.

I don't know of any other relay that serves that function, but there are plenty of solid state circuits that duplicate that functionality.

Thanks Steve. But wouldn't blocking the AC power to the track stop the train from running while the 'magnet' is working? If the aforementioned whistling tender works on DC current, the AC would still need to be present to operate the locomotive right?

Thank you gunrunnerjohn. In this case, it sounds my best bet would be just to salvage a Lionel whistle relay, and somehow fit it into my project. Question answered, and thanks to all.

@trainman48 posted:

Thanks Steve. But wouldn't blocking the AC power to the track stop the train from running while the 'magnet' is working? If the aforementioned whistling tender works on DC current, the AC would still need to be present to operate the locomotive right?

Not blocking AC *to* the track, just *from* the pickup under the tender to the relay inside, so AC would continue to flow to the engine and anything else connected. As GRJ IIRC correctly notes, the OEM whistle relay has a special construction that allows it to block and ignore the regular track AC, yet react to any DC offset. My old-school electronics brain informs me that putting a choke in-line with the coil of a standard DC relay and  a high-value capacitor across the relay coil would tend to block and divert the AC, yet permit any DC offset to activate the relay. I've never attempted to do this, and as I said before the components I mentioned above would tend to be a bit bulky, and I'm sure GRJ or others can suggest some better (and more contemporary) gizmos to do the same thing. Good luck, in any event!

@trainman48 posted:

Hi all,

I've had a few prewar Lionel whistling tenders, and was told when the whistle button on the transformer is pressed, it sends out a DC signal through the tracks, activating the relay coil and connecting the points.  If this is true, couldn't a magnet be wired to the relay rather than the whistle motor? And further, are there any smaller relays currently on the market that operate on the same principal as the bulkier Lionel unit? This is for a special project and would appreciate any information regarding this.

More uses for the relay:

https://ogrforum.com/...2#175145952028797572

Here's the circuit that Lionel uses in their set whistling tenders.  Just stick a relay in where that motor is and you're set.  I suspect any generic NPN Darlington transistor would work for the switching element.