use of RadioShack 12v 60 ma lamps on DCC for detection

[joegib]

I've been reading up on the use of LED's and lamps...but am still a little hesitant... I have many Radioshack 12v lamps (very small, red and green) and would like to use them to indicate when certain circuits are toggled on/off in my DCC HO layout... can I just wire them up directly.. ie, on a DCC "run" , hook the lamp to railA and other lead to railB wires?   and on the DCC "prog" , hook the lamp to ProgA and other lead to ProgB?   my plans are to have multiple toggles hooked up so that I can select many paths (Run, Prog, DC operation) to different sections of track...   but concerned that I"m missing something...     any help would be appreciated...    thanks joeg

[MisterBeasley]

Welcome aboard! 

If these are incandescent lights, yes, you can do that, but....

You will probably have 12-14 volts on the track.  12 volt bulbs will work, but they probably won't last very long.  You could add a resistor, or wire 2 bulbs in series so they only get 6-7 volts each.

60ma doesn't sound like much, but these things add up.  If you're connecting them to your track power, they go on the accounting books in the same column as "Trains," and you're limited by the capacity of your DCC system.  10 bulbs like that is 0.6 amps, probably more than most locomotives.  That's why it's better to use LEDs for any indicators that will be connected to your track power.  They use far less of that precious power.

joegib

and on the DCC "prog" , hook the lamp to ProgA and other lead to ProgB?

That might not work well at all.  The programming track has limited power, and putting a light bulb across it could make it impossible to program anything, and besides that, the bulb might not work.  A programming track needs to be "clean," because it has to sense proper connection of a locomotive, decoder and motor before it will do anything.

joegib

my plans are to have multiple toggles hooked up so that I can select many paths (Run, Prog, DC operation) to different sections of track..

Please, promise me you won't do that.  Do not mix DC and DCC on your layout at the same time.  It's a recipe for disaster, most likely an expensive one involving burned out decoders and DCC systems.  All it takes is a pair of wheels crossing from a live DC section to a live DCC section.

[richg1998]

A diode with a 1k, 1/4 watt resistor will require about 9ma of current. My NCE Power Cab has the same in the connection panel and works very well.

A resistor to limit voltage for a 60 ma light will be quite larger wattage.

Rich

[rrinker]

 Wiring lights of any sort to the DCC track won't provide any sort of detection It will simply tell you when that track section has power. To get actual detection of a train, you need to either check for current flowing or use some sort fo beam break detector.

 ANd do not hook anything up to the program track outputs. It's already a reduced current line and putting unexpected loads on those lines may cause you to not be able to program decoders.

  You do not want to hook up wires from the program track to multiple locations around the layout. One dead-end siding perhaps, but best of all is a completely isolated (physically as well as electrically) piece of track. Bridging the gaps between the program track and the running track can damage the command station, or cause all of your locos to be programmed. Crossing DC and DCC can also dmaage equipment. If you have a need to use both DC and DCC, the best way is to install one DPDT center off toggle feeding power to the layout, which selects between DC or DCC. Mixing them on adjacent tracks is only asking to cause damage to something because you WILL overrun the blocks and link the DC and DCC sections through the pickups on the locos and/or the decoder if it's a DCC loco. Something will let the magic smoke out when that happens.

                       --Randy

 

[richg1998]

Some years ago our club tried running DC in some blocks and DCC in others.

We wiped out a NCE 5 amp booster when a loco crossed a boundry. Never think it will not happen to you.

Rich

[DigitalGriffin]

if it were me....I would use a current based detection.

Take an iron core...pass ONE LEG of your track bus main though it
Wrap a wire around the iron core a couple times.  Measure the output...keep wrapping a couple times.  Hook each end of the wrapped wire to a full diode bridge.
Take the + side of the full rectifier bridge and hook it to a + side of a 24V capacitor and then to a the base of a transistor.
Take the - side of the full rectifier bridge and hook it to the - side of a capcitor and then to a ground.
Hook a 12V power source to the collector on the transistor.  On the emmiter of the transistor hook a resistor (2.4kOhm) and a led+.  led - side, hook to ground.

If you want to detect when the section has power (train or not) run a full bridge diode (rectifier) from one bus wire to the other.  On the rectifier +, put a resistor 1KOhm will do) and then hook the other end of the resistor to the rectifier - after putting it through the iron core center listed above.

[joegib]

Randy,, thanks for your advice... I'm actually building a test bed of two straight tracks..(not a layout).   using DPDT switches...  I was planning on using the switches to select each track as either pgm or run   and additionally have one of the run tracks selectable for DC or DCC  (the DCC end being fed by a DPDT switch for selecting run or pgm)   However,,, I do understand that the pgm wire is of a very minimal voltage and having that feed going thru possible 3 DPDT switches is not advisable..

additionally I was going to put in a DPDTswitch to select between a PR3 vs PGM.. which I'm assuming is OK as long as its tied directly to a single track and not any other switches.  

I was incorporating a PR3 unit so that I can learn about PC interfacing with the DCC system.    (I'm a retired Computer Specialist... so love to learn about new technologies)  

 

But now that I'm reading you correctly,,, the PGM leg should only have one DPDT switch to the rail... and the PR3 is similar (its like a PGM leg)  and these should not be feeding any additional DPDT switches to downgrade the voltage...

That being said..... heres my final plan based upon your comments...

Switch1  DPDT (PGM vs RUN)   to track 1

Switch 2  DPDT (DC vs RUN)  to Track2   (and now setting up a 3rd track)

Switch 3  DPDT (PR3 vs RUN)  to Track 3

Thus I can RUN on all three tracks 1,2,or 3...I PGM on only track1,,, and DC on only track2 and use PR3 on only track3. 

I'll use indicator LED's (not using 12v lamps) on only the RUN, and DC side of the DPDT switches.  and not hook up any to the PGM or PR3 sides.   

I know I'm being picky on a lot of this... but I'm trying to setup a way to learn about DCC and have a test bed on my hobby bench that gives me various ways of learning ways that DCC functions...   

any of your comments are appreciated...    Thanks   joeg

 

[mlehman]

The problem with running DC and DCC on the same layout isn't really distributing the correct signal to the track you want it on. Yes, you can do that with switches easily enough, although you would want to use a DPDT center-off to do it -- if you do.

The problem comes from running trains -- and they sometimes wiill cross the gap between your carefully separated power distribution. Instantly, the different power mix as a metal wheel even for just a second bridges that gap...POOF!

You've let the smoke out in a very expensive way.

Just saying what the others have, slighlty differently.

People sometimes do have a spur set up as a programming track. To do this the recommended way is to include a short segment of track that can be set to be dead. That way, if a wheel crosses out of the correct zone, it hits only dead rail. Unless you want to also incude such dead segments at each and every one of the potential interfaces across gaps between different forms of power, then you are taking your chances on toasting things with just a moment's inattention.

[joegib]

Mike.. your confirming what others have warned me about...and I'm going to act on it... I believe you've convinced me to just have a single dedicated DC track and not have it connected in anyway to DCC.   The three tracks I have are not physically connected in any way so they are isolated completely.  I'm heeding your warnings that if something will go wrong with the switched DCC vs DC setup.. it will go wrong.   So my third track will be a dedicated DC track for DC trains only. 

I thank everyone who put me straight on this.. and I hope to learn more about my up and coming DCC system.   Actually my DC track is going to be for bringing my old DC locos up to running well on DC (cleaning, tuning, etc)  then possibly converting them to DCC with additions of decoders..      I'll try to keep you informed with pics of my test track arrangement...    I don't have room for a full layout.. so this will be my entry into the new DCC technologies...    thanks again  joeg