Call this an old-school electronics problem. I'm lighting a brass steamer at the moment and realizing that while the headlight is no sweat (a bridge rectifier, a resistor and an LED and my work is done), the tender backup light poses a challenge because the tender is all one polarity. It seems like there are two possible solutions: I could either run a wire with a plug connector from the loco, or find some way to install a pickup for the right rail inside the tender. Anybody else had this problem recently, and which solution did you prefer? Or did you come up with something else?
P
How about using pieces of copper clad circuit board with pickups soldered to them. The assembly can then be glued to the trucks next to the insulated wheels. The turnout tie strips that are used to hand lay turnouts would work great, and Kadee coupler box springs are easily modified to make excellent wipers.
I would suggest using epoxy to mount the ties strips to the truck. I also suggest soldering the wipers to the circuit board material before gluing the assemblies to the trucks because the heat from soldering can damage the epoxy.
http://www.handlaidtrack.com/CopperHead-HO-Scale-PC-Board-Ties-p/ch-ho-s.htm
http://www.kadee.com/htmbord/page634.htm
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
One solution often used with DCC is to simply tap into track power by using the left rail power already on the tender and using it instead of blue wire + power from the decoder. Then you only need the yellow wire - power to the tender B/U light to control it.
You didn't say whether it's DCC or DC, though, and I can't recall which you use. If DC, then you'll need to either add a connecting wire to the loco or to add another pickup on the tender.
Mike Lehman
Urbana, IL
Sorry Mike, should have specified that-- I'm DC. But Dave, I really like the idea of the PCB tie hack! I can sort of visualize it, but do you have a photo?
I might actually go for a belt-and-suspenders job-- the backup LED I installed on my plastic bash was originally tender-pickup only, but I got a much more consistent beam (less flickering) once I ran connecting wires over to the loco as well. That would give the motor in the brass engine more pickups too, which aren't necessary but can't hurt.
P,
OK, on DC you'll have to add a pickup for the other side of the circut. You'll also need a diode to allow only forward current in the reverse direction. Not sure you need a complete bridge rectifier (4 diodes), just the right arrangement of 2 diodes IIRC. I get a bit dyslexic when it comes to electrickery, but if you Google "half-wave LED circuit" or something similar, you should come up with the right arrangment.
pt714
I have used copper plated circuit board to add power pick ups to several HO steam locomotives and tenders, but never on brass. However, the frames were metal so there shouldn't be much difference. The brass tender trucks that I have seen usually have a flat surface on the bolster (not sure if that is the right term), the cross piece between the truck sides. If yours does, then mounting the circuit board should be easy. The arms on the Kadee springs can be bent outward to make contact either on the back of the wheels or on the tread.
If you can post a picture of one of the trucks we could probably give you a better idea.
Have a look through this thread. The tender trucks are delrin in the thread so that allowed the springs to be mounted directly to them. In your case you will have to do something similar to the power pick ups mounted on the locomotive:
http://55n3.org/cars/tender_wipers/
This is a Kadee spring used as a wiper on a brass tender for motor power (DC). The circuit board material is affixed to the bolster with contact cement, but the ones I'm doing now (for brass locos) use two-sided board, whch can be soldered to the bolster:
These are used in conjunction with wipers on the drivers, too. The tender trucks are rotated to put the insulated wheels on the same side as those on the loco, resulting in all-wheel pick-up - no worries about short wheelbase locos on unpowered frogs.
To get the power from the tender to the motor (or, if you want to bring power from the motor to the back-up light) I use mini plugs available at electronic supply stores:
Wayne
I think doctorwayne's post will answer all your questions. One thing to note in Wayne's picture of the truck is that the wire leading from the truck up through the tender floor is very well insulated. Putting some shrink tubing around the wire will guarantee long term reliability.
If you can't find the sockets Wayne used, try these guys. Great source!
http://www.digikey.com/product-detail/en/310-93-164-41-001000/ED7064-ND/103571
This is golden stuff-- thanks, all of you! I did the soldering work this morning. If it works once the liquid electrical tape has dried, I'll post a photo or two soon, but I basically did exactly what Wayne showed on the tender truck.
Going back to Mike's post, I wonder why go through the trouble of a half-wave rectifier at all? So far I've had no trouble with a very simple circuit-- LEDs in parallel with the motor, with a 1K 1/2-watt resistor on one of the LED legs, and a bridge rectifier on the headlights so it lights in either direction. In the testing I've done so far, nothing has fried-- maybe due in part to the low current draw of the can motors? Are current limiting/blocking components more important in circuits with older motors?
pt714Going back to Mike's post, I wonder why go through the trouble of a half-wave rectifier at all?
It's a circuit that can save a wire between the loco and tender. For instance, you could drive the backup light from your loco in DC, having it come on when the front headlight turns off in reverse. This is particular trick is really useful with DCC installs, where you can have 6 wires or more between the loco and tender. With DC, it's typically the one wire, so more for keeping things tidy and self-contained in the tender.
The other instance when I've used it if for adding LED lighting in DCC without needing a decoder. I have a Walthers wedge plow I added lighting to, which doesn't get set out on the layout, but passes to and from staging. Thus the light being on all the time is not an issue. I could add an on-off micro-switch if I wanted lights off for some reason.