Railroad Signal Driver

Posted on Feb 6, 2014

This circuit can be used for lighting a single (prototype) railroad signal. You could use this to drive a model railroad signal, but only if it is for a static display - for this circuit is not designed to be interfaced with anything. DCC systems, computers, or otherwise. I`ve used variations of this circuit for over 25 years to control many other things around my house,

Railroad Signal Driver
Click here to download the full size of the above Circuit.

and they never (ok, very rarely) fail me. It relies on the venerable 555 timing chip. This circuit is simple and reliable. I`ve used small microprocessor chips do to similar things in the past, but they never seem to last as long before something needs to be replaced. It also eliminates the need buy a programmer, to write a program, and then uploading that program into the microprocessor. Email me if you have any questions. 0. 2 For the purposes of this write-up, the schematic and circuit description are for a Pennsy dwarf position light that can display four aspects: slow clear, slow approach, restricting, and stop signal. The common bulb #4 stays lit for the first three aspects. For restricting, #4 goes out, and #1 and #3 light up. This is why, later on when we get to the description on the driver circuit, we wire bulb #4 to the normally closed contact of the relay. The circuit however, can be used on any signal, even a full blown B&O CPL with all four colors and six markers (you`ll just need 10 driver circuits). 0. 3 Some of the circuits used for the individual circuits descriptions will differ slightly from that of the final single circuit at the bottom of the page. 1. 1 The signal controller circuit is pretty simple. I can be broken down into three sections, as shown to the right: 1) the oscillator, 2) the counter/decoder, and 3) the driver circuits. 1. 2 As mentioned before, the oscillator (aka: clock) uses a 555...

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