I have a variety of Tomar Industries Signals, dwarfs and searchlights, that are 3-wire signals with separate red and green LEDs. The white wire is connected to the positive (+) side of a DC power pack, and the red and green wires are resistored and connected to the #6 and #7 tabs on the Tortoise. A black wire from the #5 tab on the Tortoise is connected to the negative (-) side of the DC power pack.
Recently, I installed some additional Tortoises. I am using some 3-leg bi-polar (red/green) LEDs on a control panel. The center leg of the LED is resistored and connected to the negative (-) side of the same DC power pack. The other two legs of the LED are wired to the #6 and #7 tabs on the Tortoise. A wire from the #5 tab on the Tortoise is connected to the positive (+) side of the DC power pack.
So, all of this raises a question in my electronically illiterate mind. With my Tomar signals, the wiring to and from the Tortoise is positive (+). With the 3-leg bi-polar LED, the wiring to and from the Tortoise is negative (-). If I understand this correctly, the LED determines the polarity of the internal switches on the Tortoise.
I believe the right side of the following figure matches both of these description except the polarity is reversed – in the former, the common (#5 tab) is (-) and in the later it’s (+).
Switches typically aren’t polarized, they make a connection and pass current in either direction. I wouldn’t say the polarity of the switches.
But as you described above, you have two 3-terminal LED devices. Both are effectively two LEDs with one leg from each LED
Thanks, greg. So, polarity of the supply is the correct terminology.
I drew a diagram of my setup. Another question. If I want to wire another dwarf signal, this time to the Tortoise on the right side of the diagram, I assume that I need to use the other set of switches on the Tortoise since the polarity of the dwarf LEDs will be the reverse of the 3-leg LED. Is this correct?
that’s what I would think because you have to deal with two different LED devices that have different (+/-) commons.
it might be worth considereing replacing the panel LEDs with ones that have the same polarity as the signals to avoid the extra wiring. On the other hand, it may be possible to rewire the signals to have the same polarity as the panel LEDs (without replacing any LEDs).
With what you have that is correct. The Tomar signals are called common anode and the three legged LEDs you have are common cathode. With the signals, you probably don’t have a choice, but you could replace the control panel LEDs with common anode LEDs and you could wite the signals and panel LEDs in parallel using only one set of the tortoise contacts.
One minor point - three-legged LEDs are not bi-polar. Bi-polar LEDs have only two legs and you pass the current through them in one direction to light one LED and the other direction to light the other LED.
I agree with Robert. They are probably refered to as Bi-COLOR LEDs. I use bi-polar LEDs in series with the Tortoise power leads. Nice and easy, two legs of the LED, if the color is wrong just switch the wires. Look at the Tortoise info sheet for several methods of using indicator lights.
Miniatronics maybe lost something in the translation.
