Post War Diesel Horn Battery Eliminator

There was an article published years ago on how to make a battery eliminator.

Unfortunately, I don't recall which magazine had it, or when it appeared.

If anybody knows, or has a newer design, I'd appreciate knowing about it too.

A few years ago, there was a dealer at York who was selling a battery eliminator for post war diesels.  I don't remember who it was or much about the product but it seemed like a good idea.  I believe it was some sort of capacitor.

Wouldn't a BCR with a shape adapted to the postwar diesel do the trick?  I would think there would be a big enough market for a company like J&W Electronics to develop one.

Phil

I checked on a BCR and was told that it wont hold a charge long enough for the Pre War horn which was only a bike horn, but something that can get power from the track to trickle charge a Nicad D cell would work fine. 

Those bicycle horns really draw a lot of current. I tried to make one out of a regulator, diodes, current limit resistor and a big capacitor. I stuffed it all into a 'D Cell' sized plastic tube I made. I only had limited sucess. I couldn't fit a capacitor big enough to hold enough charge.

I read a story of someone who had sucess using a a 'fuzit' resistor. Something from old tube TV days. As far as I can tell a fuzit is only a diode and a current limit resistor in series.

Regards,

Dallee and J&W both use some kind of diode to charge there BRC's and BRC's so there must be a diode or something that can emit a trickle charge to the D cell. It would probably be popular at first like the BCR and I would think the 9 volt BCR sales are slowing down since everyone that wanted then have them. I installed BCR's in my MTH and BRC's in all my TMCC locomotives and will purchase if I buy a locomotive in ebay I'll upgrade it unless the previous owner hasn't already done so. One word of advise if you upgrade the 3.6 Volt Proto 2 save at least one of the original packs in case you need to reprogram as it won't recognize the bcr, and if returning to the manufacture for repair you might want to remove the BCR and replace the battery since I had a friend that didn't and later found his Proto 2 Locomotives BCR was replaced with a new battery.

Why not just put a voltage regulator and bridge rectifier in the battery compartment to power the horn?

What do I need to buy?

You need a bridge rectifier, a fairly large electrotyic cap, say 4700uF 50V, and a LM317T regulator.  Add a resistor to set the regulator voltage and you're all set.

I'm nowhere near my main computer (at the beach), or I'd post a schematic.  Here's the resistor values for an LM317 to generate the 1.5V.  I'm suggesting a bridge rectifier instead of the transformer and diodes.  I'm also suggesting a larger cap.

Great and Thank you John, I'll get the parts and try one out. There is still a month before school opens so It will keep me occupied. 

Normally the body of the horn is grounded to the locomotive frame, and acts as part of the circuit. Would one need to insulate the horn from the frame to use the circuit drawn by John?

Good point, you may have to either isolate the horn or include an isolation transformer.  I forget this is a project that wants no modification of the locomotive.

Isn't one side of the battery to frame ground?  If so, that's all you need.

quote:

Isn't one side of the battery to frame ground?  If so, that's all you need.

Yes, but the battery is an isolated source.

With the eliminator circuit, I think the bridge rectifier will provide a path from the center rail to horn body.

I guess the bridge is out.  OTOH, for 1.5V output, we don't really need a bridge, all we need is one diode in a half-wave rectification circuit, that will not present the same issue.

I always think bridge for conventional because I don't want to lose half the voltage, but in this particular case, that's not an issue.