There are very small Adjustable Voltage Regulator modules readily available on ebay that will allow you to use a 1.5v bulb with a DCC decoder without using a resistor in series with the bulb. The benefit is that the bulb will always benefit from a stable 1.5v source that does not vary based upon track power. An example of one of these regulators is like in the picture. I have attached a diagram that shows how to connect one of these regulators. Do not connect one of these regulators directly to DCC track power. http://www.ebay.com/itm/Mini-MP1584...Than-LM2596-/191095423493?hash=item2c7e2cc205
