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Video PSX-AR Auto Throw, Turnout Gaps and Correct Polarity

Posted by on Feb 26, 2015 in Tony's TV |

Tortoise Switch Motors

Larry is at again, solving a common issue you may encounter using the PSX-AR and Auto Throw

Hi Erik and Larry, I’ve been trying to get an auto reversing loop on my layout to operate with a PSX-AR SC with Peco turnout and Peco snap coil switch motor.  Have a look at the video below to see the issue I’m having.  
Basically a lighted passenger car, moved slowly and with downward force applied to it, will cause the switch to throw every time.  But a locomotive doesn’t seem to trigger the snap coil motor, even though the AR senses the short and cuts power to protect the booster.  Any idea what could cause this or how to solve it?   Are there any CVs or settings to adjust within the AR that may affect its sensitivity or anything? Thanks for your help!    John B.  Houston, TX

John, the basic problem is the PSX-AR is not reversing with the engine. Instead, it is detecting a short and turning off. Looking at your video, there is a conflict issue between the reverse loop and the switch. It appears that the reverse loop shares rail insulators with the switch. This can cause a situation in which changing the polarity of the DCC does not fix the short, and the PSX will then trip. For this reason, we recommend that the rail insulators for the reverse loop be located at least your longest engine away from any insulators associated with the switch. It is also good practice to stagger the two rail insulators at the end of the reverse loop by about an inch. The easiest thing for you to try would be to leave the frog insulator where it is, and locate a second insulator your longest engine length (including double heading) away from this insulator (into the reverse loop). Obviously, this short length of rail has no power, so you need to run a power feed to it from the “normal” DCC. This means connect power to this rail as if it were just a normal rail out of the switch. Wired correctly, you should be able to bridge the rail insulator with a quarter and get the PSX to reverse. Then quarter test the other end, and it should go back. Make sure that the closest reverse loop to the switch direction (e.g. when the points are thrown, the first reverse loop insulators that the engine touches) has the polarity in phase. This means no voltage across the rail insulator, which you can measure with a meter or just use a light bulb to show there is no voltage.
Hope this helps.