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LED Wiring puzzle.......

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LED Wiring puzzle.......
Posted by howmus on Tuesday, February 12, 2008 9:22 PM

OK, all you wiring ex-spurts out there.  I have decided that the toggles on my facia for my hidden staging just aren't going to be able to be used correctly by most people who may come over for operations on the SLOW (mostly because I can't seem to get it right easily myself). Therefore in the interest of smooth operations, I have decided to put in a small control board at the site of the staging for ease of use. (It also can be used for one of the requirements for the NMRA Model Engineer Electrical AP Award that I have almost done.) The control board will use bi-color LEDs to show when a route is open through staging (this staging is actually a loop with three tracks).  A hand drawn track scematic is shown below:

The turnouts inside the staging loops are shown as circles and numbered 1, 2 , 3, & 4.  The turnouts are thrown with Toroise machines controlled by standard DPDT Toggle switches. The easiest place to power the LEDs would be directly from the toggles I think.

The question is.........  How would you set up and use the LEDs to show the open route?  I'm talking how to wire them, how many, what would be the clearest way to lay the whole thing out on a small control panel.........??????

Ray Seneca Lake, Ontario, and Western R.R. (S.L.O.&W.) in HO

We'll get there sooner or later! 

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Posted by larak on Tuesday, February 12, 2008 10:50 PM

Here's one solution.

Wire the LEDS in series with the tortoise motor leads for 1 or 2. Green for the active route, red for the two others. You only need one LED per route.

1 down 2 up = green on inside red for route to middle or outer.

You can use the switch contacts of 1 to feed one end of the middle / outer LEDS through  both red or off. Feed the other end through contacts from 3 or 4. Bring lead to common for one color and reversed double voltage for other. don't forget current limiting resistors. This requires a split power supply or at least a comon ground between two supplies.

I know it's not terribly clear but it's my bed time. If no one posts a diagram I will try tomorrow.

Karl 

The mind is like a parachute. It works better when it's open.  www.stremy.net

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Posted by BlueHillsCPR on Wednesday, February 13, 2008 8:47 AM

Well, I've spent a few hours trying to wrap my head around the solution Karl suggested and I can't quite draw up a circuit diagram to illustrate the idea more clearly.  Karl, if you can draw something up for what you suggested I know I would be enlightened by it! Smile [:)]

After thinking about it I thought this might be more simply operated by using a three position rotary switch to choose between the inside, middle or outer routes and a single DPDT toggle to activate the tortise in the appropriate direction once the route is chosen by the rotary switch.  Add the LED indicators and I think that would be almost fool proof. Just my My 2 cents [2c]

Edit: Then it occurs to me that you wouldn't need a three position switch at all...and since turnouts 1 & 2 and turnouts 3 & 4 really need to operate in sync, you would only need two DPDT toggles to switch the routes. 

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Posted by howmus on Wednesday, February 13, 2008 12:59 PM
 BlueHillsCPR wrote:

Edit: Then it occurs to me that you wouldn't need a three position switch at all...and since turnouts 1 & 2 and turnouts 3 & 4 really need to operate in sync, you would only need two DPDT toggles to switch the routes. 

 

AHA!!!  You are right!  I never saw that.  I can use just 3 Bicolor LEDs to show the active route.  On one each possible route.  That would be very easy to wire and do.  I would just run the Torti #1 and #2 together, and #3 and #4 together in parallel.  It would, I believe require two LEDs on the Middle and Outer loops which are the main storage tracks  anyway.  If one is green and the other is red, the route is not active.  If both are green, the route is selected and it is safe to proceed.  The inside could get by with only one LED as the route is selected only by torti 1 & 2. 

Thanks!  I think that will work. I will try putting the LEDs in series with the torti.  I am using a 9 volt wall wart for powering the tortis.  Hopefully there will still be enough voltage to light the LEDs.  A Tortiose has about 600 ohms of resistance which would be about right for 12v.

Ray Seneca Lake, Ontario, and Western R.R. (S.L.O.&W.) in HO

We'll get there sooner or later! 

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Posted by BlueHillsCPR on Wednesday, February 13, 2008 3:10 PM
 howmus wrote:
 BlueHillsCPR wrote:

Edit: Then it occurs to me that you wouldn't need a three position switch at all...and since turnouts 1 & 2 and turnouts 3 & 4 really need to operate in sync, you would only need two DPDT toggles to switch the routes. 

 

AHA!!!  You are right!  I never saw that.  I can use just 3 Bicolor LEDs to show the active route.  On one each possible route.  That would be very easy to wire and do.  I would just run the Torti #1 and #2 together, and #3 and #4 together in parallel.  It would, I believe require two LEDs on the Middle and Outer loops which are the main storage tracks  anyway.  If one is green and the other is red, the route is not active.  If both are green, the route is selected and it is safe to proceed.  The inside could get by with only one LED as the route is selected only by torti 1 & 2. 

Thanks!  I think that will work. I will try putting the LEDs in series with the torti.  I am using a 9 volt wall wart for powering the tortis.  Hopefully there will still be enough voltage to light the LEDs.  A Tortiose has about 600 ohms of resistance which would be about right for 12v.

Yes, I think you can simplify the whole thing quite a bit.  I think the LED drop down resistance for 9 volts would be aprox. 350 OHMs.  The two tortises in parallel would be 300 OHMs.  Seems like it should be just about right if you wire the LED's in series with the two tortise motors acting as the resistor wired in parallel...maybe someone else can verify this?

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Posted by howmus on Wednesday, February 13, 2008 6:39 PM
 BlueHillsCPR wrote:

Yes, I think you can simplify the whole thing quite a bit.  I think the LED drop down resistance for 9 volts would be aprox. 350 OHMs.  The two tortises in parallel would be 300 OHMs.  Seems like it should be just about right if you wire the LED's in series with the two tortise motors acting as the resistor wired in parallel...maybe someone else can verify this?

If my figuring is correct (and the Ohm's Law online calculator works), the LEDs I am getting can have a maximum Voltage of 2.8v and would be using 30mA of current.  That makes them 93 Ohms.  So if the Torti running in Parallel have 300 Ohms plus the 93 Ohms of the LED placed in series with the Torti, that should balance out a 9v curcuit with 22.9 mA of current and .2 watts of power....????  Am I correct?  If I am the curcuit should be a wire and play.

Ray Seneca Lake, Ontario, and Western R.R. (S.L.O.&W.) in HO

We'll get there sooner or later! 

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Posted by BlueHillsCPR on Wednesday, February 13, 2008 8:29 PM
 howmus wrote:
 BlueHillsCPR wrote:

Yes, I think you can simplify the whole thing quite a bit.  I think the LED drop down resistance for 9 volts would be aprox. 350 OHMs.  The two tortises in parallel would be 300 OHMs.  Seems like it should be just about right if you wire the LED's in series with the two tortise motors acting as the resistor wired in parallel...maybe someone else can verify this?

If my figuring is correct (and the Ohm's Law online calculator works), the LEDs I am getting can have a maximum Voltage of 2.8v and would be using 30mA of current.  That makes them 93 Ohms.  So if the Torti running in Parallel have 300 Ohms plus the 93 Ohms of the LED placed in series with the Torti, that should balance out a 9v curcuit with 22.9 mA of current and .2 watts of power....????  Am I correct?  If I am the curcuit should be a wire and play.

It sounds dead on to me but I am no engineer.  If one of the guys here who I know are E.E.'s come along I'm sure they can shed more light on this.  Guys? 

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Posted by Anonymous on Thursday, February 14, 2008 4:54 PM
I wouldn't put the LED in series with the Tortoise motor at all. It's an inductive device and when powered the surger currents and reverse voltages are going to kill the LED sooner than later. I would find a way to wire them separately. I'm too lazy to study what you're doing so I'm not commenting on that. Also most LEDs are maxed at 20mA not 30mA so you may want to double check the specs on the ones you're going to use. BTW I don't have an EE degree but hold the title of Engineer. Hope I helped! - Randy
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Posted by howmus on Thursday, February 14, 2008 5:14 PM
Randy, the specs are right off the Radio Shack page for these LEDs.  That is a very good point about the Torti being an inductive device.  I may just put it in parallel in the circuit and use an appropriate resistor.  That would probably be the safest.

Ray Seneca Lake, Ontario, and Western R.R. (S.L.O.&W.) in HO

We'll get there sooner or later! 

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Posted by BlueHillsCPR on Thursday, February 14, 2008 7:00 PM

Wiring in parallel with a resistor will work too. The idea of using the tortise as the resistor comes directly from an American Hobby Distributors tip. Confused [%-)]

http://www.amhobby.com/products/tech/circuitron/wiring-leds.htm 

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Posted by jrbernier on Saturday, February 16, 2008 7:48 PM

  Wire them in series with the Tortoise motor!  The motor only draws about .015-.018 Amps at stall, and the LED will be protected.  My layout has them done this way, and our club has dozens of them wired like this.  The advantage is:

  • Less wiring
  • No need for extra toggle or Tortoise contacts
  • The LED will 'dim' when motoring over to the opposite position(positive proof it is moving) and return to full brightness when the Tortoise motor 'stalls'. 

  BTW, we only use a 15 VAC(850 ma) wall wart to power the all of these Tortoises.  The actual voltage is reduced by the LED's and we wanted the points to move slow to start with.  This kind of wiring keeps things real simple(only 2 connections to the Tortoise edge connector(and it can be flipped if the switch throws the wrong direction).

Jim Bernier(never burned out a LED or a Tortoise since 1992)

Modeling BNSF  and Milwaukee Road in SW Wisconsin

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Posted by howmus on Saturday, February 16, 2008 8:23 PM

Thanks Jim.  That's what I will do.  One of them will need two LEDs wired in parallel and then wired in series with the 2 Torti.  But that should work with no problem.

The nice thing about this little project is that it will eliminate 2 toggle switches and really simplify the movement of trains in and out of staging.  

Thank you all for your input. 

Ray Seneca Lake, Ontario, and Western R.R. (S.L.O.&W.) in HO

We'll get there sooner or later! 

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Posted by CSX Robert on Saturday, February 16, 2008 10:22 PM
Using a diode matrix you could wire up a double pole rotary switch so that when you turn the rotary switch to the route that you want the turnouts would align for that route, the green LED for that route would light, and the red LED's for the other two routes would light. This could also be expanded to as many as six routes using a single 2 pole 6 position rotary switch. The wiring would definitely be more complicated, but the operation would be about as easy as it gets - no toggles to throw, just the single rotary switch to select the route. If you are interested, I could come up with a wiring diagram for you.
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Posted by jbinkley60 on Sunday, February 17, 2008 3:55 AM

 howmus wrote:
Randy, the specs are right off the Radio Shack page for these LEDs.  That is a very good point about the Torti being an inductive device.  I may just put it in parallel in the circuit and use an appropriate resistor.  That would probably be the safest.

You would be safe wiring the LEDs in series with the Tortoise machines.  I have done this with single and dual Tortoises off of either a panel switch or a stationary DCC controller (i.e. DS64 etc).  The current limiting resiatance of the Tortoise will keep the LED current at a safe level.  No resistor should be needed.  If you wire the LEDs in parallel, you will need a resistor.  Someone mention a concern about the Tortoises being inductive.  They are but they are small enough that this shouldn't be a concern.  All LEDs and silicon rectifiers have a higher peak current than steady state current rating.  This will provide a safey margin.

Here's a document which may help.

http://www.tonystrains.com/download/man-tortoise.pdf

You may also find that the 9V supply is not enough.  I generally used 12V and with that and the LEDs in series you end up with 9-10V or so at the Tortoise.  This may or may not cause it to run slower than you would like.

 

Engineer Jeff NS Nut
Visit my layout at: http://www.thebinks.com/trains/

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Posted by locoworks on Sunday, February 17, 2008 4:32 AM
you could buy 4PDT switches instead and use the spare contacts, or you could use the spare SPDT switches on the tortoise machine itself ( assuming you have one spare with the other used for frog polarity? ) and run wires back to the control panel to feed the LED's
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Posted by howmus on Thursday, February 21, 2008 8:03 PM

Just want to post an update.  I have started the panel and have started the wiring.  Here is the basic plan for wiring up the board.  The scematic will be repeated for each of the two DPDT Toggles controlling the routes into and out of the staging loops.

If this is not correct, someone please say somthing before i fry the LEDs.......Wink [;)]

In actual fact since the torti are already mounted in place and to make troubleshooting and repair easier, the parts will be wired through a 6 space terminal strip set up for it.  again one terminal strip for each toggle system.  Hope that makes sence to you.... 

Ray Seneca Lake, Ontario, and Western R.R. (S.L.O.&W.) in HO

We'll get there sooner or later! 

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Posted by jbinkley60 on Thursday, February 21, 2008 8:38 PM

 

Are you still planning on bicolor LEDs or are these individual color LEDs with the polarity flipped between them ?  If you are using bicolor then only one LED is needed (although you could use two just to show two track indicators).  If they are individual color (i.e. red and green) then just ensure you flip the polarity on them and then match them to the direction of the turnout throw (i.e. make sure that green lights when you have the switch flipped in the right direction etc..).  If the LEDs light but in the wrong color (i.e. red lights instead of green) then reverse the polarity of both LEDs.

 

Engineer Jeff NS Nut
Visit my layout at: http://www.thebinks.com/trains/

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Posted by howmus on Thursday, February 21, 2008 8:57 PM
Yes, they are the bi-color LEDs.  There will be one on each of the possible routes through the turnout.  If the route is OK to use the light will be green if not red.  Yep I will have to wire the LEDs one each way so that one is green and the other is red for each toggle.  I should have showed that in the diagram.  I will have to do the same thing with the torti to make sure they throw the right direction....  Thanks.

Ray Seneca Lake, Ontario, and Western R.R. (S.L.O.&W.) in HO

We'll get there sooner or later! 

JMB
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Posted by JMB on Tuesday, March 18, 2008 9:16 PM
Ray..

Jim Bernier mentioned he is using 15 VAC for his Tortoise Controls;

Are you using AC or DC in your diagram?

(I know it sounds like a stupid question but I want to be clear as I delve into the intricacies of these wiring tips!)

And what program did you use to create your diagram?

Thanks!

...John


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Posted by jrbernier on Tuesday, March 18, 2008 10:51 PM

  I use 15VAC and split it with a pair of diodes to make a polarized power source(plus, minus, & common).  The wiring is described in the bottom of the Tortoise instructions.  The advantage is that there is less panel wiring(I used sub-minature SPDT toggles from Mouser Electronics).  Either way will work fine(I have some very large panels for the club staging, and went the 'polarized' route).  here is a link to a copy of the Tortoise install doc.  I used the #3 wiring scheme:

http://www.amhobby.com/download/man-tortoise.pdf

  Just wire the '2 wire' bi-color LED in series with the center lead to the Tortoise motor like in example #4.

Jim Bernier

Modeling BNSF  and Milwaukee Road in SW Wisconsin

nof
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Posted by nof on Thursday, March 20, 2008 2:36 AM

Hello Howmus!

This is almost exactly what I did with my Inglenook Puzzle. I made a panel with three pushbuttons and three bicolor leds. I push the butten for the track I want connected to the main and the electronics (two relays and some diodes) and tortoises will fix it for me.

You find a description here look under turnouts.

If you are interested I can supply you with schematics. 

Nils-Olov Modelling the tomorrow in N-scale.

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