rodshaw Posted November 23, 2017 Share Posted November 23, 2017 I have two live frog turnouts facing each other, separated by insulating rail joiners. If the points are set in opposite directions, so that their respective frog polarities are different, a loco going over the insulated joiners from one turnout to the other obviously produces a short circuit. This isn't a real problem because my DCC system just shuts down and I can easily change the points to the right direction and re-start. But my question is - can I wire an LED into the circuit to come on as a warning if the points are incorrectly set? The way I see it, any wiring connecting the turnouts so as to turn on this light when the polarities are opposite will itself produce a short circuit. The only thing I can think of is to have four LEDs, say two red and two yellow, two each for the different polarities, so I know the loco can proceed if the two same-coloured LEDs are lit. Or am I missing something? Link to post Share on other sites More sharing options...
Griffin Road Posted November 23, 2017 Share Posted November 23, 2017 Morning , Can I please ask how you change/operate the points before we answer ? Cheers Mike b Link to post Share on other sites More sharing options...
Junctionmad Posted November 23, 2017 Share Posted November 23, 2017 I have two live frog turnouts facing each other, separated by insulating rail joiners. If the points are set in opposite directions, so that their respective frog polarities are different, a loco going over the insulated joiners from one turnout to the other obviously produces a short circuit. This isn't a real problem because my DCC system just shuts down and I can easily change the points to the right direction and re-start. But my question is - can I wire an LED into the circuit to come on as a warning if the points are incorrectly set? The way I see it, any wiring connecting the turnouts so as to turn on this light when the polarities are opposite will itself produce a short circuit. The only thing I can think of is to have four LEDs, say two red and two yellow, two each for the different polarities, so I know the loco can proceed if the two same-coloured LEDs are lit. Or am I missing something? a diode in series with a suitable Led dropping resistor and an LED wired across on of the insulators ( not across the track ) will illuminate anytime the DCC polarities are opposite Link to post Share on other sites More sharing options...
rodshaw Posted November 23, 2017 Author Share Posted November 23, 2017 Morning , Can I please ask how you change/operate the points before we answer ? Cheers Mike b Each frog is wired to a microswitch and the polarity is changed via a pushrod, as in this upside-down photo: Link to post Share on other sites More sharing options...
rodshaw Posted November 23, 2017 Author Share Posted November 23, 2017 a diode in series with a suitable Led dropping resistor and an LED wired across on of the insulators ( not across the track ) will illuminate anytime the DCC polarities are opposite Ooh, that sounds neat. I knew there had to be an electronic solution. And I think I have the necessary components to hand. Which way does the diode have to point in relation to the LED? Link to post Share on other sites More sharing options...
cliff park Posted November 23, 2017 Share Posted November 23, 2017 One other simple option would be to screw another microswitch on top of each existing one, simply longer screws, and use those to work some LEDs. Link to post Share on other sites More sharing options...
Penrhos1920 Posted November 23, 2017 Share Posted November 23, 2017 a diode in series with a suitable Led dropping resistor and an LED wired across on of the insulators ( not across the track ) will illuminate anytime the DCC polarities are opposite ..but if the system just shuts down as a loco goes over the insulators doesn't that mean there is no power to light the led? Link to post Share on other sites More sharing options...
rodshaw Posted November 23, 2017 Author Share Posted November 23, 2017 (edited) ..but if the system just shuts down as a loco goes over the insulators doesn't that mean there is no power to light the led? I need the light to come on whenever the points are set wrongly, as a warning to set them correctly before the loco gets there. Otherwise there's no point doing it. Edited November 23, 2017 by rodshaw Link to post Share on other sites More sharing options...
Junctionmad Posted November 24, 2017 Share Posted November 24, 2017 (edited) I need the light to come on whenever the points are set wrongly, as a warning to set them correctly before the loco gets there. Otherwise there's no point doing it.Yes the led will light the moment the polarity of the two sections is opposed , yes it will go out on a short , but then so what. The diode " faces " the same way as the LED. , typically you would have a series resistor , led , diode , in that order Edited November 24, 2017 by Junctionmad Link to post Share on other sites More sharing options...
cliff park Posted November 24, 2017 Share Posted November 24, 2017 Use double switches, as I said, and a totally separate power source for those LEDs, even a battery to try it out. Link to post Share on other sites More sharing options...
rodshaw Posted November 24, 2017 Author Share Posted November 24, 2017 Yes the led will light the moment the polarity of the two sections is opposed , yes it will go out on a short , but then so what. The diode " faces " the same way as the LED. , typically you would have a series resistor , led , diode , in that order So are we saying... Link to post Share on other sites More sharing options...
DCB Posted November 24, 2017 Share Posted November 24, 2017 a diode in series with a suitable Led dropping resistor and an LED wired across on of the insulators ( not across the track ) will illuminate anytime the DCC polarities are opposite This is a non DCC section and the LED solution won't work with DC as DC voltage fluctuates drops to zero as trains stop. The two switch solution will work for DC as long as long as there is room for the additional microswitches in addition to frog polarity switches and routeing switches. The short is an issue for both DC and DCC, DC as it destroys plunger pickups on the Airfix 14XX etc and damages the thin springy pickups on most current RTR, and DCC because it shuts the layout down, trains stop abruptly and like as not the trains derail. Making sure the crossover is reset is an issue, I use direct finger prodding and diode matrix and switching half a crossover back and not the other half is a regular occurrence! Link to post Share on other sites More sharing options...
RMweb Premium dhjgreen Posted November 24, 2017 RMweb Premium Share Posted November 24, 2017 This is a non DCC section and the LED solution won't work with DC as DC voltage fluctuates drops to zero as trains stop. The two switch solution will work for DC as long as long as there is room for the additional microswitches in addition to frog polarity switches and routeing switches. The short is an issue for both DC and DCC, DC as it destroys plunger pickups on the Airfix 14XX etc and damages the thin springy pickups on most current RTR, and DCC because it shuts the layout down, trains stop abruptly and like as not the trains derail. Making sure the crossover is reset is an issue, I use direct finger prodding and diode matrix and switching half a crossover back and not the other half is a regular occurrence! The OP has mistakenly posted this in non DCC but states in the first post that their system is DCC. Link to post Share on other sites More sharing options...
rodshaw Posted November 24, 2017 Author Share Posted November 24, 2017 The OP has mistakenly posted this in non DCC but states in the first post that their system is DCC. It wasn't a mistake. My system is DCC but I posted the question here because it didn't seem to be a DCC specific issue. As I can still switch to DC as backup, a solution for both would be ideal but a solution that only works for DCC is fine in practice. So for DCC, will the wiring diagram I posted above work? Link to post Share on other sites More sharing options...
RMweb Premium dhjgreen Posted November 25, 2017 RMweb Premium Share Posted November 25, 2017 (edited) So for DCC, will the wiring diagram I posted above work?Should do, just make sure both the "arrows" are pointing in the same direction. Back to back copies of the circuit would work in DC, but only with a train moving. Edit, or use a bridge rectifier. Edited November 25, 2017 by dhjgreen Link to post Share on other sites More sharing options...
Junctionmad Posted November 26, 2017 Share Posted November 26, 2017 So are we saying... LED wiring.jpg Yes the led and the diode " face " the same way. Link to post Share on other sites More sharing options...
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