does anyone know what resistor values to use for rolling stock detection and signaling. I'm going to the Digitrax BDL168, and my track current is 15 volts.
I have 2 axles, each with a 10K resistor, on my cars. One resitor axle in each truck. Most of the others in the club have one detected axle per car with a 4.7K resistor. The detectors are sensitive enough to detect a single 10k, when it makes good contact (clean wheels, clean track) and I like having one resistor per truck, that way if a car is stopped straddling a block boundary, it's detected in both as is proper. The others think I'm nuts for making twice as many resistor wheelsets, but once you get on a roll you can crank them out pretty fast in assembly-line fashion, with different groups at various stages of production. And mine are probably more difficult since I use Proto 2000 metal wheels - the axles are plastic, slippery plastic, so I have to rough up a strip so the CA and resitor sticks and also so the conductive paint sticks. And the wheels are blacked so they need some polishing where the wheel meets the axle so the conductive paint works. Many of the others run Intermountain, which have metal axles so all you need to do is glue in a resistor at an angle on the insulated wheel and put small blobs of conductive paint bridging the contact points to the wheel and axle.
A strong magifier, and some of the thick CA are my tricks, because if any of the CA gets on the edges of the resistor where the contact points are, it will be useless. A tiny toothpick dab is all it takes, and while the thick stuff takes longer to set, it also doesn't easily flow away from where you place the tiny drop. And of course tweezers to hold the resistor.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
couldn't you just solder the resistor to the back of the wheels with a dab of CA or superglue for good measure?
I also use 10kohm resistors. One per truck same as Randy. I use rrcirkits block detectors on my personal layout but the 10 kohm seem to work on just about any layout I have run on, be it CMRI, digitrax or rrcirkits block detectors.
As Randy mentioned I am one of those who use the intermountain wheelsets with the metal axles. I model the 1980's so by that time the ribbed back wheels were being phased out.
Another thing to note is don't skimp on the conductive paint. I do not have the exact brand of what I use but the silver paint conductive pens are junk. The jar of paint I have is used for repairing damaged pcb's and was $35.00 for a one ounce jar however it was worth it since it makes a perfect connection every time. The conductive paint pens were givinge failures on 8 of 10 wheelsets.
Another thing, use a multimeter to test you wheel sets before installation. This will verify that no glue got on the resistor Co tact and that the conductive paint is doing its job.
Colorado Front Range Railroad: http://www.coloradofrontrangerr.com/
If you look at one of the resistors you might see why this would be difficult. It's probably doable, at the risk of breaking down the insualtion at the wheel hub. Certainly not doable on P2K wheelsets, the axle is plastic. Complicated by the fact that the resistor would need to sit at an angle on the Intermountain wheels. Much, much easier to glue it on with a dab of CA and then use conductive paint. It's not cheap stuff, so whatever you do, don;t accidently spill it - $30+ for a bottle of the GOOD stuff, and by 'bottle' I mean maybe 1/2 ounce. It has real silver - I got mine on ebay, it's also used for electron microsopes. However, even with having to paint a strip all the way across the P2K axles (IM wheels would use a lot less), I did 100 wheelsets and still have over half the bottle left. When using this stuff you need to contantly shake it up, the silver settles out from the backing medium VERY quickly.
There are probably cheaper alternatives, which might mean experimenting with different resistor values - there are conductive carbon pens but they have a much higher resistence so you would probably use smaller value resistors.
Slightly scary at first - the conductive paint does not conduct very well until it dries. If you attempt to check just a minute or so after painting the conductive line, it will still show as an open circuit. The stuff I used takes at least 15 minutes before it finally passes current. My test setup has my meter clipped to a piece of track, and a good resistor wheelset will show the approximate 10K calue with just the wheelset sitting on the track, not back in the truck or anything. I have one final step after they show good, I put them in a wheel painting jig and paint the faces grimy black, and spray the backs and axle with flat black to hide the shiny silver paint, and protect it. One final check of the resistence and they are ready to go back on the cars.
Does anyone sell a package of wheels with resistors on them? Sounds like it would be easy to insert in manufacturing process. I would pay $1 for a pair.
Yes, Jay Bee makes wheelsets with resistors already installed. About $30 a dozen. They seem to not be making them anymore though, some sites say they have one pack left in stock and they can;t get any more. Logic Rail Technologies has them, $8.94 for 4 wheelsets. Litchfield has their own, though their product description is copied word for word from Logic Rail, or vice-versa. $1.98 per wheelset.
The resistors are cheap. It's the paint that gets you - I think I have the 20% silver paint, but I'd get 40% I think if I need more - 30 grams of paint, $65. But, I did 100 wheelsets and used less than half my bottle.
With Intermountain metal wheels with metal axles, you can do something like this: http://www.teamdigital1.com/applications/tech_talk/resist_wheel.html More drag, and some cars might not have the clearance, but it's cheap and easy.
I use metal wheels with plastic axles. I also use 10k 1/8 watt axial resistors (for HO scale wheel sets). I wrap the leads around the axles next to the wheels and hold the resistor body in place with super glue, then use wire glue from All Electronics to form the electrical contact between the wires and wheels.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
I think I'm missing somethign here - got a pic? You say you wrap the leads around the axles, and then use the wire glue to link the lead to the wheel (obviously one on each side) - how does that work when the axle has to turn inside the wrapped lead?
This is the 'easy' way with metal axles, just put the insulated wheel on opposite sides (won't work with metal trucks though) and then simply wrap the resistor lead around the axles, no conductive anything needed. I just don;t see how this can possibly work with plastic axles, any conductive paint would be quickly scratched off via friction with the resistor leads.
I use the BDL168. I purchase one pack of the Logicrail resistor wheel sets and then made the rest using Intermountain wheels, 10K resistors, CA, and conductive paint. One per car.
Dave
Lackawanna Route of the Phoebe Snow
Randy, the resistor is glued to the axle so it turns with the wheels. Everything rotates together.
OK, now it makes sense. All other examples using a leaded resistor drape it across two axles in a truck, not parallel to the axle. I do have some cars where that would not work, a 1/8 watt resistor is too big (the SMD ones were too - I had to make some with the resistor off-center).
Randy:
As you can see from the picture I posted of an HO wheelset, I use 10K surface mount resistors. They are as good as invisible when installed on the train.
That's what I use. Your picture illustrates how much easier it is to do with Intermountain wheels as opposed to the P2K ones I have in all my cars. I don't have any handy pictures, and the site I followed appears to now be gone.
I think if I switched to IM wheelsets I'd build a jig that stand them up at a 45 degree angle to apply the resistors - I used the smaller (4 axles) of my wheel painting jigs to hold the P2K ones to glue the resistor to the center and draw the lines to each side with the conductive paint. After the first few, and getting over the initial "omg, none of these works" when I tried to test them before the paint was fully dry, I got good at the assembly line method and churned out the ones I needed in a couple of evenings.
Oh yea. I should have mentioned that the conductive paint is an insulator until it dries. I hold mine in the 4 axel wheel painting jig, too.
Here is a diagram I came up with a few years ago to illustrate how I do my resistor wheelsets with the intermountain wheels.