LEDs on Model Railroad

You're correct Joe, you need a device known as a flip-flop to latch to lamp status. Additionally, you'll need a clean and steady source of DC to power the device and a small circuit to clean the signal(s) that moves the solenoid.

Tell us about the solenoid, does it activate a rotary mechanism that alternately moves the track? What I'm asking is if the solenoid is pulsed or whether you supply it one polarity to route the train onto the first track and then the other polarity to route the train onto the other track? I'm guessing the latter case based on the SPDT switch. If so, you can use an inverse parallel set of LEDs and a limit resistor to indicate which way the train will route.

An actual link to your Atlas track switches would be most helpful. I also have no clue what a DCC style train is although I have seen N gauge models.

This

switch

SPDT

location or

power

the

It is a *pair* of solenoids. No rotary mechanism. A momentary pulse is sent to one or the other solenoid to switch the tracks. No continuous power is sent to the switch track.

The web site I visited is

I have a couple of guides/handbooks from about 1979 which indicate that these switch tracks are just a pair of solenoids and a straight-line motion that moves the track back and forth.

DCC is what I *don't* have. It's a digital system for controlling multiple locomotives on the same tracks.

My locomotive control is apparently just a rheostat controlling about 15 volts of DC, which is probably just full-wave rectified. I doubt if it is even filtered.

I read somewhere that these switch tracks can be operated on around 15 V of either AC or DC. So maybe running them from some small DC supply would make it simplest to connect in an IC flip-flop.

--- Joe

Okay Joe, thanks for the clarifications. What you need to do is to continue to connect the solenoids the way you do currently. It is clear that the solenoids are not effected by the throttle position, that is good.

The easiest way I can think of is to tap a line off of each solenoid and condition this to be compatible with the flip-flop. The solenoids are run by an unknown voltage so you should determine if it is AC or DC first and then what voltage. Once this is known, the signal is made to operate the LED portion of an opto- isolator. The reason for the opto is so we don't have to share a ground between the train supply and the flip-flop.

You will need an SR flip-flop. The Set & Reset inputs will be driven by the receiver side of the opto. You will also need to construct a (typically) 5 volt DC power supply that will run the optos, the flip-flops and the LEDs. You may want to include a power on clear for the flip-flops but they will be okay after one cycle of the track switch.

Lets hear what your solenoids are being driven by, AC or DC and what voltage. Once this is known, then we can make it run the LED side of the opto.