can i make detectable whlsets with resistance paintgreenspun.com : LUSENET : Wiring for DCC : One Thread
can kadee or other metalic wheelsets be painted with resistance paint or graphite type pigments to provide detection for dcc control. if so where can this type of paint be purchased or can i add powdered graphite to enamel or laquer vehicle?
anybody do this with success?
-- legief trebor (firstname.lastname@example.org), December 15, 1998
Sure, did it for years, about 30-40% pencil carbon mixed with Polly S will give you about 10K across the axles. I used to get the carbon from the old rotary drafting pencil sharpeners.
I would recommened a much easier, cleaner and absolute resistance method today. I currently use 16 watt SMT resistors, and conductive epoxy or ciruit trace pen. Just super clue the resistor to the axle, then run the traces out from each end to the inside wheel hubs. With KaDee, make sure you clean the black off the areas of the insides of the wheels where the conductive material will make contact. I use a 20K resistor on the outside axle of each car, this will give a effective resistance across the rails of 10k.
Digikey is a good source for 1/16 watt SMT resistors. And Circuit Works makes conductive circuit trace pens and epoxy both.
Remember Always Have Fun and Enjoy!, Don Crano Akron, Oh NMRA #096211 mailto:email@example.com Visit Model Railroading with DCC at: http://pages.sssnet.com/donc/
-- Don Crano (firstname.lastname@example.org), December 15, 1998.
If I may piggyback a few questions at this point!
1. Why 2 10K instead of 1 20K?
2. How many cars can have this mod within a consist?
-- Jaime M. Valdez (email@example.com), June 10, 2003.
Why use two resistors instead of one? What if the car is straddling a block? Worse, what if that block being straddled happens to be a turnout? You could have a car fouling a turnout and not know it. That's probably the worst scenario and the reason two instead of one. Also note that the resistors go on the outside wheels to minimize car being somewhere it shouldn't be and you not know it.
Before I answer your second question, let me address a technical issue to make sure no one is confused. The resistors on the car are in parallel. Two 10k in parallel would be 5k. Two in series would be 20k.
Various block detection systems require different maximum values. Note that if a manufacturer says that their maximum value is say 10k, even if you use two resistors, it would be a good idea to use 10k. Why? If one axle is fouling a turnout, you want to trigger the block for the turnout and do no want to count on the two resistors on a given car to do so.
Your second question, how many resistors/cars can you have in a consist like this? All you want. You would have to have about 350 cars, with two resistors each, all powered BY THE SAME BOOSTER, to draw 1 amp of power. (Most boosters can supply several amps, usually about 3 or so. )
Probably the only way to have this happen is to have an absolutely huge yard powered by the same booster. If you have a single yard big enough to hold that many cars, can I come play trains at your house or club?
Bottom line: You have nothing to worry about. Put the resistors on all the cars you want.
Note: Atlas wheelsets, my favorite for soldering resistors to, have become nearly impossible to buy. Also, soldering resistors to wheels is not trivial for everyone. So, despite the cost of resistive paint, we are experimenting with using SMT resistors and resistive paint or possibly the mixture suggested by Don Crano in an earlier email. Look for a potential change in the website if we like either of these approaches better.
-- Allan Gartner (bigboy@WiringForDCC.com), June 10, 2003.