The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
Thanks, Randy, this is all very interesting.
It never crossed my mind that the two different signals would be in conflict with one another until I tried it today.
Rich
Alton Junction
To flip a 2 lead bicolor LED with a SPDT set of contacts you'd need AC and a pair of extra regular diodes - pretty much the same sort of thing you do to run a Tortoise itself with a SPDT switch shown in the instructions. Or a bi-polar DC supply, in which case you could probbaly use the same common for both types of LEDs - just that one power supply will have extra load because in addition to powering all the bi-color LEDs set for that indication, it would also be powering ALL of the dual LED signals. Not a showstopper, but it needs to be accounted for.
Like this crude ms paint picture I drew:
I drew it as if the 2 LED signals are common cathode, if they are common anode just flip the two power supplies around at the bottom. 4 resistors because Tortoise contacts have a tendency to sometimes make before break so both could be active at once. As you can see, the right hand power supply will run ALL the 2 LED signals, plus whichever of the bicolor signals are set for theat indication, so worst case would be all signals driven from that one supply. Resistor size is based on voltage of one supply, so if you use for example a pair of 12V supplies, and the LEDs are 2.1 volts 30ma max, you'd want about a 680 ohn resistor which is 15ma, or maybe down to 470 if they aren't very bright LEDs.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thanks, Randy, I was afraid of that.
Could I use the other set of three terminals on the Tortoise for the other Tomar signal or would the white (common) wires still cause a conflict?
Let me think about that one. I think they will conflict. If it was a 3 lead bi-color LED, it would be essentially the same as two discrete LEDs with a single common, but since it's a 2 wire bi-color, it needs to be wired differently. The 2 lead bicolor LEDs need a simple polarity reversal,DPDT switch type. 3-wire configurations, either 2 LEDs or a 3 lead bicolor LED, need a SPST type swutch to direct power to one or the other outside lead. The two-lead signals could be wired across the motor terminals of the Tortoise, with a resistor, while one set of contacts could control the 2 LED signals.
I have a fair number of Tomar Industries signals, both searchlights and dwarfs, on my layout, and each is connected to a Tortoise with the green and red wires from the signal.
The Tortoise is controlled by a DPDT toggle switch which receives its power from a 12 volt power pack.
The electrical circuit for the signal consists of a Tortoise wire connected to one terminal on the DC power pack, while the white wire from the Tomar signal is connected to the other terminal on the DC power pack.
The Tomar searchlight signal is a 2-leg bi-polar red/green LED. The Tomar dwarf signal is a pair of 2-leg LEDs, one red and one green.
Is it possible to power both types of signals from the same terminals on the Tortoise?
Or, will the bi-polar LED conflict with the single color LED?