D cell eliminator for PW diesels

Gunrunnerjohn is the man to ask on how to do this. You would need a charging circuit with built in rectifier of some type to put out 1.5 volts  dc from the ac track voltage and then a capacitor to store the voltage. Some time ago there was at least one thread about this and Gunrunnerjohn was mentioning ways to accomplish this. I personally have two Postwar Lionel engines that use the D cell batteries. Every time I know I will use the engine I will add the battery and after the running session remove the battery. It is really not a big deal to do this. It is only a big deal if you forget to do this and battery leakage results from leaving a bad battery in. Besides I like to try and keep all Postwar Lionel engines as original as possible (just my opinion).

Coincidentally, yesterday I was at the Dollar Tree store and bought two packs of D cell batteries (4 total batteries) to use in the PW F-3's this Christmas season.  They'll go in for horn tests and come out when the Christmas layout comes down.

Still, I'll be particularly interested in what GRJ may have to say.

thanks guys...I sent Gunrunnerjohn an email....joe

I have built a circuit board that fits in a D or C cell adapter:

https://ogrforum.com/...23#66610802182583723

I use an AC to DC buck converter set to 1.5 volts. The plus goes to the whistle relay and the minus goes to the frame of the horn which must be insulated from the frame. The horn is insulated by gasket material between the horn and the frame, and then mounted with nylon screws. The input to the buck converter is connected to the frame of the engine and the pickup rollers. The buck converter is mounted in place of the D cell.

David Nissen posted:

I use an AC to DC buck converter set to 1.5 volts. The plus goes to the whistle relay and the minus goes to the frame of the horn which must be insulated from the frame. The horn is insulated by gasket material between the horn and the frame, and then mounted with nylon screws. The input to the buck converter is connected to the frame of the engine and the pickup rollers. The buck converter is mounted in place of the D cell.

What is a "buck convertor?"

It's useful to show how the buck converter was wired.  Depending on the model, you may have to isolate the horn totally, I attempted to avoid that hassle.

gunrunnerjohn posted:

What is the 1.5V current when horn is activated?

Stan, using a sample of one, it's around 200ma.  I find that having a cap across the output helps the horn get going, doubtless a small higher current shot to kick start it.

thanks to all,especially Gunrunnerjohn.....problem solved...joe 

gunrunnerjohn posted:

Stan, using a sample of one, it's around 200ma.  I find that having a cap across the output helps the horn get going, doubtless a small higher current shot to kick start it.

Interesting.  So what I was imagining was finding one of those 99-cent DC-DC buck converters that has a reverse-polarity input protection diode.  This diode effectively makes the module a half-wave AC-DC converter.  The question about current goes to the relatively small bulk capacitance (say, only 100uF) that comes on these DC-DC modules.  But if the output current is "only" 200 mA at 1.5V and you're starting from 10V or more of AC track voltage, a half-wave converter might be good enough!  That is, with a stepdown buck converter, 200 mA of output current would require much less input current vs. a linear stepdown LM317-type design which would also require 200 mA of input current.

This would get around the isolation issue vs using a bridge-rectifier AC-to-DC module.  Would need to find a DC-DC buck converter with input protection diode that goes down to 1.5V on the output, has enough input capacitance to ride-out the half-wave rectification, etc. etc.  Just thinking out loud...

Addendum:

From a recent post, here's an example of the reverse-protection diode on a DC-DC converter module which effectively makes it a half-wave AC-DC converter module albeit severely handicapped by a small input capacitor (100 uF shown) which limits its regulated output current capability.

There are tons of ways to skin this cat Stan, I suspect the buck converter with the diode would work as well.  Considering the 1.5V at 200-250ma, the 100uf input cap at a much higher voltage would probably be sufficient.  I use 300uf on my Super-Chuffer for a 5V switcher at around 80-100ma, no problem with half-wave power there down to about 11 VAC on the track.

stan2004 posted:

From a recent post, here's an example of the reverse-protection diode on a DC-DC converter module which effectively makes it a half-wave AC-DC converter module albeit severely handicapped by a small input capacitor (100 uF shown) which limits its regulated output current capability.

Stan, I looked at one of those supplies with a reverse-protection diode, but the diode is directly across the +/- inputs.  How would that make it a half-wave AC-DC converter, my thinking is on the half cycle that the diode conducts you'd either cook the diode, the wiring, or trip the fuse/breaker.  Am I missing something?

Depends on the module.

In above DC-DC stepdown module, you can see from the copper islands under the soldermask that IN+ goes to the anode of the diode...and the cathode of the diode goes to the "+" side of the 100uF input capacitor.  Additionally, note that the SS34 is a Schottky type which is used for low forward voltage which you'd want in this configuration to reduce power loss.

As for modules that put a diode in-reverse directly across the DC input pins, I suppose that provides "some" protection but seems short-lived and ill-conceived  That is, if you hook the module up backwards (or to an AC source) it seems the diode would quickly cook and fail.  If that diode fails in the "open" state, the input source is still hooked up, but your protection is gone and "valuable" electronics would fry.

In any case, the bigger picture is even if a DC-DC module does NOT have a protection diode like the one I show above, you can always add a 5-cent diode in front of a 99-cent DC-DC module.  Then it becomes a matter of determining if there's enough capacitance to maintain 1.5V DC output during the AC half-cycle when power is not available.  That's why I was asking about the Horn current.  

Joe

Another solution to the D cell battery corrosion of regular and especially alkaline batteries to consider is using rechargeable NiMH D size cells. 

I have been using rechargeable NiMH cells for years for cameras and flashes and have not had one ever leak.  If they did leak, I do not believe they will corrode like regular and alkaline batteries.   I leave them in my cameras for months and do not bother to remove them while waiting to be used.

NiMH rechargeable batteries hold there charge for many months if not years.  They also last for years and I have several that are older than 10 years and still work fine.  They can be recharged hundreds of times.  The D size is available at eBay in the Tengery brand for D size cells at 10,000 mAH at four cells for $20 (maybe available at less than 4 cells). 

This may be a less trouble and possibly a lower cost solution to the D cell issue with older Lionel diesel engines.

Charlie