LEDs/Spring Wire/Application Notes for Tortoise

You can fabricate it from 0.039" music wire. Made by K&S -- most hobby shops stock it -- in the Walthers catalog:

Circuitron has a "catalog & application book" for $6.00. My copy is only 40 pages long; I see that the latest is up to 52 pages. Besides describing their products, part of the book shows how some of their products can be combined to solve specific problems. Among the applications in my copy of the book are: - Single track grade crossing - Single track, 3 grade crossings - High rail (Lionel) grade crossing - Multiple track grade crossing - mainline - Multiple track grade crossing - sidings - Crossing gates using the Tortoise - Rolling stock detector - Manual override of optical detectors - 2 color block signals - High rail (Lionel) 2 color block signals - Block signals with automatic train control - 3 color block signals - Automatic reversing - point to point - Automatic reversing - point to point with siding - Automatic reversing - with delay and intermediate stops - Automatic reverse loop switching - Non-derailing turnout control - Automatic stop and delay with slowdown - Automatic train stop on a blind siding - Trolley, mine line or switching layout - Crossover control - Accessory lamp sequencer

I got the book to help me with non-derailing turnout control to set up some optical sensors to control a tortoise machine so that tthe turnout is correctly aligned for trains departing either of my staging tracks. (Despite the fact that I am an engineer by profession, electrical circuits are my weak point in this hobby and I found the book and their products very helpful.)

The book is $6 -- currently out of stock at Walthers but expected at the end of this month.

I wish they just offered the "applications" part of their book as an on-line reference. Making the material easily available would spur a lot of new products sales by encouraging people to use their products in ways not thought of before.

The other set could be used to power indicator lamps on a control panel.

Chris wrote:

"Music wire" is available at a good hobby shop. It is a very springy steel wire. It should be possible to make a new spring wire from a piece of music wire of the proper diameter.

LED's are pretty much all the same. They differ only in color, physical size, and maximum rated current. Used to be all LED's required 20 milliAmperes (mA) to light to full brilliance. Now a days a lot of LEDs out there are "hi efficiency" types that only need 10 mA. All Light Emitting Diodes are rectifiers. Biased forward (DC applied plus to minus) they light up, and conduct like a closed switch. They have NO internal resistance to limit the current thru them. You have to supply an external resistor of the right value otherwise they blow out. Instantaneously. Which converts them into Darkness Emitting Diodes (DED). For 12 volts DC, 470 ohms is good for the 20 mA types, 1K is about right for the 10 mA types. Biased in reverse (minus to plus) LEDs are dark. If the reverse bias exceeds 6 volts many LEDs blow out and become DEDs. So you want to be careful to install the LED the right way round. This is easier said than done because most LED's do not bear polarity markings. I use an ohm meter to determine which polarity makes a LED conduct. Bi colored LED's are actually two LEDs in the same package, wired in opposite directions. Biased one way shows one color, reverse the bias and you get the other color. I haven't wired tortoises my self, but they have a permanent magnet motor. Apply DC of one polarity and it turns one way, reverse the polarity of the current and it runs the other way. The motor draws so little current that the power is left on the motor all the time, it doesn't mind being powered up even when the turnout has reached end of travel and stalled. There are several ways the wire the LED.

1. You can put a bi colored LED in series with the tortoise motor IF and ONLY IF the it draws less than 20 mA. I seem to remember they draw

50 mA but I'd have to check a data sheet to be sure. This circuit has the benefit of indicating good wire all the way out the the tortoise and back. If the tortoise fails or the wire breaks, the LED doesn't light in either direction. A useful trouble shooting aid.

1. Put a bi colored LED with a current limiting resistor across the tortoise motor. This works, but the LED will stay lit even if there is a broken wire running out to the tortoise.

Try the circuitron web site. They must have one.

in article UPGwc.84591$ snipped-for-privacy@twister.rdc-kc.rr.com, Mark Mathu at snipped-for-privacy@mathu.com wrote on 6/6/04 8:34 AM:

All the app notes you likely need are packaged with each tortoise machine. I installed my tortoise system using the two DC power pack scheme (#2 on the app notes). I installed two wire 5mm bi-color (red/green) leds in series with the center SPDT switch with no resistor and it works perfectly.

"David J. Starr" , In a message on Sun, 06 Jun 2004 12:51:45 -0400, wrote :

"JS> "JS> "JS> "JS> Chris wrote: "JS> > "JS> > A few questions regarding Tortoise Switch Machines: "JS> > "JS> > 1. I have lost the spring wire for a Tortoise Switch machine. What would "JS> > make a suitable replacement? Where can I find it? "JS> "JS> "Music wire" is available at a good hobby shop. It is a very springy "JS> steel wire. It should be possible to make a new spring wire from a "JS> piece of music wire of the proper diameter. "JS> "JS> > "JS> > 2. I'm considering using Red/Green LED's or bicolor LEDs to indicate switch "JS> > position on control panel. As an electrical newbie, what is a good LED "JS> > to use for this purpose? (Manufacturer/Model number)? Thanks. "JS> "JS> LED's are pretty much all the same. They differ only in color, physical "JS> size, and maximum rated current. Used to be all LED's required 20 "JS> milliAmperes (mA) to light to full brilliance. Now a days a lot of LEDs "JS> out there are "hi efficiency" types that only need 10 mA. All Light "JS> Emitting Diodes are rectifiers. Biased forward (DC applied plus to "JS> minus) they light up, and conduct like a closed switch. They have NO "JS> internal resistance to limit the current thru them. You have to supply "JS> an external resistor of the right value otherwise they blow out. "JS> Instantaneously. Which converts them into Darkness Emitting Diodes "JS> (DED). For 12 volts DC, 470 ohms is good for the 20 mA types, 1K is "JS> about right for the 10 mA types. "JS> Biased in reverse (minus to plus) LEDs are dark. If the reverse bias "JS> exceeds 6 volts many LEDs blow out and become DEDs. So you want to be "JS> careful to install the LED the right way round. This is easier said "JS> than done because most LED's do not bear polarity markings. I use an

Commonly, one lead is a little longer than the other. Some LEDs may also have one side 'flattened' to indicate polarity.

Have a look at this PDF file (a page out of the Mouser Catalog) for details on LED polarity markings:

The Cathode gets wired to a "-" side of of the supply. The Cathode is the shorter lead and the lead next to the flattened side of the LED (some of the larger LEDs have a flattened side).

"JS> ohm meter to determine which polarity makes a LED conduct. "JS> Bi colored LED's are actually two LEDs in the same package, wired in "JS> opposite directions. Biased one way shows one color, reverse the bias "JS> and you get the other color. "JS> I haven't wired tortoises my self, but they have a permanent magnet "JS> motor. Apply DC of one polarity and it turns one way, reverse the "JS> polarity of the current and it runs the other way. The motor draws so "JS> little current that the power is left on the motor all the time, it "JS> doesn't mind being powered up even when the turnout has reached end of "JS> travel and stalled. "JS> There are several ways the wire the LED. "JS> 1. You can put a bi colored LED in series with the tortoise motor IF "JS> and ONLY IF the it draws less than 20 mA. I seem to remember they draw "JS> 50 mA but I'd have to check a data sheet to be sure. This circuit has "JS> the benefit of indicating good wire all the way out the the tortoise and "JS> back. If the tortoise fails or the wire breaks, the LED doesn't light "JS> in either direction. A useful trouble shooting aid. "JS> 2. Put a bi colored LED with a current limiting resistor across the "JS> tortoise motor. "JS> This works, but the LED will stay lit even if there is a broken wire "JS> running out to the tortoise. "JS> "JS> "JS> > "JS> > 3. Does Circuitron provide "application notes" as an addendum to their "JS> > printed instructions? How does one go about attaining them? Just write "JS> > to them and ask? Any payment/SASE required? "JS> "JS> Try the circuitron web site. They must have one. "JS> > "JS> > 4. I'm new to wiring these but I think I know what to do. I see that the "JS> > machine has 2 SPDT switches on it. I was going to use one set to power "JS> > the frog. What sorts of applications do people use the other set for? "JS> > "JS> "JS> > Thanks in advance. "JS>

\/ Robert Heller ||InterNet: snipped-for-privacy@cs.umass.edu

|| snipped-for-privacy@deepsoft.com /\FidoNet: 1:321/153

This is true, but the difference in length can be extremely small to the point that it's hard to see. Experienced folk can detect LED polarity this way, but for the casual LED user, who has difficulty remembering which lead is the long lead and whether Cathode or Anode goes to the plus side of the circuit, an ohm meter check before soldering and before applying power will save much confusion.

David J. Starr