Diodes for PTP

In 2006 I co-wrote an article on how to "soften up" the Aristo-Craft Auto Reverse Unit. I have been enjoying this feature on my point to point track where I set up diodes to slow down the loco as it enters the station at either end of the track. I run 4 axle locos and RDC cars on my point to point and they are run well with the set up. To see the loco slow down to a crawl as it enters the station looks realistic and saves on gear damage.

A few friends were over a little while back and were asking how I did it. I resurrected the article but decided to draw it up using PowerPoint to make it a little clearer and add it to my site.

For the original article in the Aristo-craft Insider magazine, click here November/December 2006 Insider

Diodes are neat as they only allow current to flow in one direction and they have an internal voltage drop of .7 volts. (some do have different voltage drops but I am not sure which ones)

I used groups of 1N54004 diodes which are rated at 3 amps. I purchase these from AllElectronics.com As you can see the following diagram and photos, I grouped 4 diodes together for a total of 2.8v drop at the first slow down point and 5.6v drop at the second slow down point. You can have as many slow down points as you want.

For the return I used 2 diodes for a 1.4v increase at the two speed up points. This helps to ensure the loco has enough oomph to get started.

Here is the diagram I drew showing the placement of the diodes.

	The below photo shows the group of diodes soldered together and connected to the track with Split Jaw Insulated rail clamp.

	This photo shows how diodes can be buried in the track ballast

	Here is the end of the track diode, again connected to the track using a Split Jaw Insulated rail clamp

	As I say in the article, diodes are cheap so here is a cheap way to give more realistic stopping and starting on your point to point. Enjoy!