- I have balked at going the route of DPDT power relay + cheap SPST switch, because it requires another power source, and added complexity (I am so new to electronics). If you recommend going this route, any pointers, schematics, pictures, etc. will be welcome.
You could use a 12 volt DPDT relay with a 7812 regulator circuit and run it off track power. This would work from about 8-18 volts on the throttle maybe even a bit lower.
The lionel electro-mechanical whistle relay is for low voltage around 3volts DC and does not pass AC. It may overheat with straight DC at 18 volts. As John mentioned it would blow the whistle with either track polarity. The mechanical E unit is also an AC coil. It will have much less impedance run on DC and prolonged use at higher voltages could overheat it. The PW type motor itself will run on AC or DC. Installing a rectifier and capacitor in series to the motor will make it run smoother and give better low speed performance. This rectifier can not be fit in some steamers.
Some PC Boards can be damaged by straight DC while others are not. The K-Line external,bell/whistle controller used a bridge rectifier and capacitor so straight filtered DC was sent to the track when the button was pushed. The lionel external controller (one design anyway) uses 6 diodes in one direction and one in the other so the sine wave is unbalanced only by about 3 volts more positive than negative or negative than positive depending on which button was pushed. So Lionel did not like the simpler K-Line design perhaps fearing damage to the solid state boards.For solid state boards the whistle will sound on one polarity and the bell if equipped will sound in the other.
Here is one way to make an external bell/whistle controller. Works best with pure sine wave transformers. If relay contacts are used in place of push buttons, the whistle/bell can be automated to blow at a crossing approach for example.
http://www.jcstudiosinc.com/Bl...2&categoryId=426
Dale H
