132 Station and 151 Semaphore, relay help needed

Are you able to create an isolated outer-rail block of the same or similar length as the isolated center-rail block?  If so, then you can use one of many readily available relays which detect occupancy when the outer-rails are shorted via wheel axles.  Cost would be between $10 to $25 for off-the-shelf products I'm thinking of.  Maybe $5 if you're willing to mess with an eBay relay module.  So let us know if cost is an issue.

If for whatever reason you can't, I'd look at concocting a circuit to sense when the "Nichrome Wire" thermostatic switch is open vs. closed.  I'm not aware of any off-the-shelf widget that can plug-and-play with the 132 to do this but maybe someone else knows of one.  A DIY sensor and relay would not be expensive (less than, say, $5) but can be tedious if you're not comfortable messing with electronic components.

I agree with Stan. Adding a relay directly to the output of the 132 (to the center rail) is not what you want to do. The additional current draw from the relay coil could affect the timing in the thermostat switch and throw off your already working station stop mechanism. It would be better to connect your semaphore in the more traditional manner and keep the two items separate.

I thought I was the only one who still uses a bimetal thermostat switch to run the furnace. Two metals that expand at different rates when heated so that the whole thing bends and adjusts the contacts to close a switch seems like a shaky way to run anything. I can't believe that Lionel hasn't updated this unit to at least use some vacuum tubes.

Stan et al. - why wouldn't just setting up a simple SPDT relay across the center rail to the outside rail do the trick?  So when the center rail is energized, the relay (I'm thinking of an automotive or similar relay that has both NO and NC outputs) is closed and wired to the 'green' semaphore position/light.  When the train triggers the 132 station relay, which in turn de-energizes the center rail, the second relay goes NO, which would be wired to the 'red' semaphore/position light.  So in this scheme the semaphore is only an indicator, it is not involved in the electrical circuitry controlling the train.

So why does Lionel use a thermostatic switch for the station relay?  Is it just to delay the firing of the relay?  I don't think Gilbert (and then Lionel) ever used these types of relays in S gauge equipment.  The Flyer semaphore, for example, has a solenoid in it - triggered by a somewhat fussy pressure-sensitive 'track trip' - that controls both the arm position and the power to the controlled section of track.

- Rich

richs09 posted:

...why wouldn't just setting up a simple SPDT relay across the center rail to the outside rail do the trick?  So when the center rail is energized, the relay (I'm thinking of an automotive or similar relay that has both NO and NC outputs) is closed and wired to the 'green' semaphore position/light.  When the train triggers the 132 station relay, which in turn de-energizes the center rail, the second relay goes NO, which would be wired to the 'red' semaphore/position light.  So in this scheme the semaphore is only an indicator, it is not involved in the electrical circuitry controlling the train.

richs09 posted:

...So why does Lionel use a thermostatic switch for the station relay?  Is it just to delay the firing of the relay? 

That's what I think.  If done today, low-cost capacitor or solid-state timing circuits would surely be more cost effective, reliable, and have more consistent/stable delays irrespective of track voltage or size of engine (i.e., the motor load).

Stan - my bad - I didn't look carefully enough at your circuit diagram.  Its an interesting - if not a wholly McGyver'd - method of stopping a train.  Gilbert included a low resistance (~40 ohms or so) resistor in the circuit so when the circuit was tripped by the aforementioned track trip, the solenoid relay wouldn't open completely, but would include the ~40 ohm resistor.  By doing so, the reversing unit (e-unit) stays engaged and doesn't trip but the track voltage is low enough to stop the engine.  The nichrome wire relay accomplishes the same task for Lionel.  At first, I thought that it might actually slow the loco as the nichrome heats up, eventually stopping it, but it looks as if the temperature coefficient for the resistivity of nichrome wire is pretty small, so even at 200 deg C the resistance is only 4% more than at room temperature (and I doubt the nichrome gets that hot in this situation...??).

When I was a (ahem) kid, I had two Flyer locos running in the same direction on the same loop of track, with a Gilbert semaphore controlling a dead block, so one train could always stay a safe distance ahead.  But I always noticed that when the trailing train entered the controlled block (and the block was dead) the engine would, of course, go from track speed to zero almost instantly - a very unprototypical behavior to my (then) young eyes - but I could never figure out how to to make the engine slow down first...

- Rich

Gentlemen, Thanks for your replies. I had looked at the insulated outside rail, as I am using it and relays for signals elsewhere on the line, but it doesn't really do what I had wanted here.  I had not really understood that the thermostatic switch still has current even when it is "off".  That explains why the relay wasn't working for me.  

Happy New Year!

Why doesn't the insulated outside rail with relay work for you?

My intent was for the semaphore to be ahead of the train, and for it to go red when the train entered the insulated block and stops with the power cut. Then when power is restored, the semaphore would go green and the train starts up. With the outside insulated rail, the semaphore would stay red until the train has gone past and left the insulated section. So while I could do it with insulated outside rail, the effect would not be what I am looking for.

Understood. 

So here's one approach.  You need to measure the voltage between 1 and 3.

When there's no train present the voltage is 0.  There is no current flowing thru the Nichrome Wire (resistor).

When the train enters the block, the voltage jumps up to some large percentage of the track voltage - I'd guess maybe 3/4 or more.  The Nichrome wire is heating up and the voltage between 1 and 3 will be easily measurable/detectable.

When the Nichrome Wire triggers the bi-metal strip, the switch shorts out the Nichrome Wire so the voltage is 0.

So you want a relay that triggers whenever there's voltage present between contacts 1 and 3.

When the Nichrome Wire is shorted, the full track voltage is available to the engine and it takes off.  The bi-metal strip cools down in a matter of seconds and the voltage between 1 and 3 drops to 0.  Of course if you have lighted passenger cars those will draw current and also create a voltage between 1 and 3.  But this voltage would be smaller (less current) than an engine so the voltage sensor could be calibrated to only detect engines.

If this makes sense we can talk about specific implementation options.

Stan, Thanks for your help. I just finished measuring the voltage. Yes, zero when no train is present, around 12 volts when train has entered and stopped.

Do you have a meter that measures Resistance (Ohms)?  If so, with the track unpowered and nothing sitting in the station block, can you measure the Resistance between 1 and 3?

Could you elaborate on whether you want a plug-and-play (no soldering, no fussing with components, minimal wiring, etc.) no matter the cost?  It's just that I can imagine solutions ranging from less than $5 to more than $20 depending on how much DIY you want to put in.  For some of us, tinkering with ways to make the railroad run better is part of the fun of the hobby...for others it's just frustrating and annoying. 

What an interesting possibility for an IR proximity sensor. I published three proximity sensor based animations controlling lights, track power, servos, etc.  Eliminates all those track based issues.         Will look further into this.

Stan,

Here is what I measured for resistance. Plug and play not necessary, this is for home, not my modular sections. I am okay with soldering and wiring as long as I am following directions in terms of what components to use, etc.

Could you confirm a good battery in the meter?

When touching the meter leads together in the Resistance mode, the needle should swing to the "0" on the top green scale...or be adjusted with the dial to do so.

The measurement in your photo suggests the resistance is about 2.4 x 1K = 2400 Ohms.  This seems somewhat large...I would have expected a somewhat lower resistance (meaning needle more clockwise).

Separately, about how long does the engine sit stopped before power is restored to the controlled block?

After adjusting the meter, the resistance measurement midway between the green 0 and the first tick to the left. (.1?)

With the current setting on the 132, the train stops for about 10 seconds.

OK - I think the stars are starting to align!  If the Resistance is 0.1 (x1K), that's 100 Ohms.

So when engine enters block , there's ~12V AC across the 100 Ohm Nichrome Wire (heater).  That's a heating power of about 1.4 Watts.  (Watts = Volts x Volts / Ohms).  1.4 Watts seems like a reasonable power level to warm up a bi-metal switch.  And 10 sec seems like a reasonable warm up interval.

This is why the original Resistance measurement of 2400 Ohms seemed odd.  That would be a heating power of only 0.06 Watts which is hard to imagine warming anything up!

Since there's 12V AC available when the engine is stopped (and the Nichrome Wire "heater" is active), the obvious solution is just hook up a 12V AC relay.

But, while 12V AC relays are certainly available, they tend to be expensive and can consume coil power on par with the Nichrome heater.  This can upset the apple cart in terms of station delay timing and such depending on how much power the relay coil steals from the Nichrome heater. 

So my suggestion is the Azatrax MRAPR-12V AC/DC relay.  This is actually a DC relay with some components to make it function as an AC relay.  The coil resistance is 360 Ohms which is several times the Nichrome Wire resistance.  It will "steal" some power but I don't think you will see a material change in behavior.

The coil inputs to the relay module would connect to terminals 1 & 3 on the 132 station.  The relay contacts of the module would go to the Accessory using the "standard" Common, Normal Open (NO), and Normal Closed (NC) connections. 

I realize some signal accessories (possibly including the Semaphore) might only need the Common and NO contacts.  So one could ponder whether a simpler (less expensive?) relay module could be used.  But in general, for signaling widgets that power red/green or up/down, you need all 3 contacts.  So with shipping, I figure about $15-$20.  Note the convenient screw-terminal connectors on the Azatrax module.

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Now all that said, one could roll-their-own equivalent to the Azatrax module for half or less out-of-pocket cost but requires soldering and gathering and assembling at the component level.   A bridge-rectifier (for AC-to-DC conversion), a capacitor to smooth possible coil chatter, and a 12V DC relay should do the trick.  Would require a dozen plus solder connections.  So less than $3 in parts cost and you'll pay more for shipping.  For example, from DigiKey.com.  Links purposely NOT provided as this was hastily searched.

What a DIY approach does provide is ability to tailor the parameters to the application at hand.  For example, the relay above has a coil resistance of 1000 Ohms...or roughly 10 times that of the ~100 Ohm Nichrome Wire heater - hence a neglible burden.

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Separately, for the sake of completeness, I was searching OGR and there have been several threads about the 132 station.  Apparently, if the Nichrome Wire / thermostatic bi-metal switch fails, a "genuine" replacement can run $25 or more and it would be re-furbished at that.  So there have been occasional discussions about how to duplicate the 132 station stop performance.  To that end it seems the direction others have taken is to use timer modules and relay modules.   For maybe $5-10 on eBay with little or no soldering, one could cobble together some modules to kill track power for some settable time delay ... and then re-apply power for some different time delay (to let engine leave the controlled block) before re-arming to stop the next pass thru.  Actually, this would be a DIY'ers playground; I was imagining how to sense the engine was approaching the station at high speed (high track voltage) which would disable the stopping and let the "express train" go thru.  Only the "local" trains approaching at slower speeds would stop.  And so on.