Vines Garden Railroad Workshop Articles

       

Slow Down Circuit For Reversing Unit

One of the problems associated with many of the inexpensive reversing units available on the market today is they do not have circuitry built in to automatically slow down the locomotive or trolley when it reaches the end of track.
The possibility exists, when suddenly removing or reapplying the voltage to the motor block, this may place undue strain on the gears and other parts of the drive train. Premature failure may result.
This certainly appears to be true of the trolley cars operating at the Vines Garden Railroad especially when operating at higher voltages and the faster speeds. Without going into elaborate and sometimes expensive solutions a very simple slow down circuit can be installed with just a few low cost power diodes.

The diodes can be built into a housing situated at the side of the track or installed on the underside of the Aristo-Craft ART-11350. (Remove the screws securing one rail and cut the rail in half. The cut itself will act as insulation between the rail.) Note the position of the slow down circuit in relation to the power feed and the stop section for the reversing unit.

The slow down circuit itself consists of a number of diodes wired in the form of a bridge with a series of diodes across the output. While this is not a perfect solution the voltage drop over diodes is sufficient to reduce the sudden torque applied to the motor. It should be noted the actual voltage drop and hence the speed of the vehicle will vary depending upon the current drawn by the motor. For most G scale motor blocks, three diodes (D5, D6 and D7) will reduce the speed by about one half.





All diodes shown in the circuit diagram above are 50V 3.0A 1N5400 (RS 276-1411)

In most cases power diodes are marked with a single band at the cathode end. Observe correct polarity when assembling.
A 50V 4.0A full wave bridge rectifier (RS 276-1146) may be used in place of diodes D1 - D4 as this may not only save some space but a couple of dimes as well!

Insulate all of the wiring and seal with a silicon sealant for both weather and bug proofing

Norman Allum - 6/24/2010