I bought some sp/st switches to turn sidings on/off. the switches have three prongs. Is the third prong a ground? Can I ignore it and simply wire hot and common to the other two? thanks.
Scrappy
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It sort of looks like that's an illuminated switch? If so, the 3rd terminal might be to light the bulb/LED.
In any event, you would NEVER want to wire both a hot and common to this type of switch(unless one may be for the bulb/LED), as you would then be connecting them together for a short circuit, right? For a sPST switch, you are connecting either the hot or ground with the switch (and it may be more complicated if you are using Legacy or DCS - see GRJ's post about DCS and sidings if you want to learn some of the challenges)
If you want to switch both hot and common, you need a double pole switch to handle both connections simultaneously.
-Dave
Since this is SP/ST and I do want to light the illuminated cap, how would I wire this?
J Daddy posted:Yes - Note the diagram below. You can actually route power to 2 different blocks with one switch if you like.
But unless he had a typo, you show a SPDT, he has SPST.
-Dave
Scrapiron Scher posted:I bought some sp/st switches to turn sidings on/off. the switches have three prongs. Is the third prong a ground? Can I ignore it and simply wire hot and common to the other two?
I think you mean wire transformer hot and siding center-rail to the other two? Otherwise flipping the switch will short hot to common which would ruin your day.
Agreed that looks like an illuminated automotive type switch. The third prong is for the internal lamp but only if you're switching 12V DC. In which case ignore it.
If this is indeed a 12V automotive-style switch (do you have a part #), and you want the switch to light up, this recent thread shows exactly what you're talking about...not expensive but does require some relays.
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I do not want complexity. ALL I want is a simple on/off sp/st switch to turn a siding off/on which lites up when power is on. Is there such a thing? I am totally ******* frustrated. Gee whiz, this seems so unnecessarily difficult.
Grrrrrrrrrrrrrrrrrrrrrrr
Are you SURE these switches are SPST (single pole, single throw) and not SPDT (single pole, DOUBLE throw)?
I ask because it would be unusual for an SPST switch to have three terminals.
Yes, Rich, it is. I do believe it is an automotive switch rated up to 120v but, admittedly, I am really not very knowledgeable about this. I ordered them from Mouser electronics and I did make sure it was sp/st. I guess I just don't know what the heck I am doing.
Elipt
Part of the problem is I assume you're switching 18V AC command voltage to the siding??
Many, if not all, illuminated automotive switches have built-in bulbs that run on 12V. I suppose if you can find such a switch where you can pop it open and swap out the 12V bulb for a 18V (or whatever) bulb then you'd be in business. I'd think though that given the nature of the automotive market, if a bulb fails in this type of switch you just replace the entire switch so you can't access the bulb?
I suppose you could add some component(s) to drop the voltage applied to the internal bulb to 12V from whatever track voltage. But that would involve making some electrical measurements to calculate a resistor value and might require soldering and component level wiring. Agreed the relay method is not simple but as shown does not require soldering though there's wiring complexity.
There are 12V illuminated automotive switch that use LEDs (vs. incandescent bulbs) for illumination. LEDs are DC powered so you can roll the dice and apply 18V AC and see if using "half" the AC voltage reliably drives the LED.
What is the Mouser part # ?
I use automotive switches with illumination in them to switch sidings. They have three terminals, one lug is labeled "Supply", one lug is labeled "Load" and the third lug is labeled "Earth". The switching occurs between Supply and Load. Connect your track voltage to Supply and your siding center rail to the lug labeled Load. Then in the case of the LED illuminated switch, which I am assuming this is, connect all the Earth terminals together and use one 1N4003 diode to supply common, the U or outside rail terminal. THE ARROW SIDE OF THE DIODE IS CONNECTED TO THE EARTH TERMINAL. 
CONNECT THE BAR OR LINE SIDE OF THE DIODE TO COMMON. That will illuminate any switch which is turned on. The track voltage of 18 VAC when applied to an LED which is a diode, is effectively now around 12 VDC. The diode action of the LED does that. Then I put all the Earth terminals together and to a diode to common to protect the LEDs from the reverse cycle of the 18 VAC.
Above is the simple wiring of the switch.
To see if the switch you have is compatible with this scheme, what are the terminals on your switch labeled? Or what is the part number? Picture of the terminals?
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The above scheme will also work for a switch which has a 12 VDC bulb instead of an LED. The diode used to protect the LED will lower the effective voltage to around 12 VDC for bulbs.
CJack,
Many thanks. I wish I better understood how you wired this. I ordered from Mouser Electronics. Tjhe part number is below. I cannot see anything on the switch terminals labels like "supply/earth/load" As a result, I cannot tell which is which. When you say, "connect all the Earth terminals together and use one 1N4003 diode to supply common, the U or outside rail terminal." Do you mean all the commons from all of the various track circuits all together? I just don't understand how I would do that and where the diode would go and so on . . . .
Mouser Part #:
540-RRA22H3BBRLN
Manufacturer Part #:
RRA22H3BBRLN
Manufacturer:
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Cjack, I assume you specifically selected an SPST automotive switch? From the other thread, I was led to believe these switches might actually be SPDT switches thereby shorting LOAD and EARTH when off.
PLCProf posted:...
1. Many of these switches (photo attached) are actually SPDT switches. The lamp is connected between the ACC and GROUND terminals. When the switch is in the OFF position, the ACC and GROUND terminals are connected.
I don't know if there is an equivalent scenario in automotive applications, but in our quirky O-gauge block powering we can get this situation (albeit rare and should not happen): An engine or lighted caboose momentarily straddles (because of the two center-rail rollers) the powered track and the un-powered siding. In other words someone drove an engine into, or backed up a consist with lighted caboose into an unpowered siding (the toggle switch is OFF). If the toggle switch is indeed of the SPDT style, this would apply full track power across the poor diode. This behavior was part of the discussion in the other thread of potential issues when re-purposing a 12V illuminated automotive switch to switching AC track voltage.
RRA22H3BBRLN
If I'm reading their datasheet correctly, the "L" in your part number specifies a 120VAC lamp...whereas I think you want the 12VDC bulb.... so part number ending ...BBRHN
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Sorry, fellas. ALL Greek to me. I assume from all of this there is NO sp/st switch anyone knows of that lights when power is on to the track. Really?
We went to the moon fifty years ago and we cannot get a switch to light without changing bulbs, diodes, friodes, transistors, transformers, reformers, performers, and the like?
In that case, since I don't know ****, I think I can wire a switch to turn power on and off and I will just wear my glass to see what ******* position its in.
Over and out.
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Scrapiron Scher posted:CJack,
Many thanks. I wish I better understood how you wired this. I ordered from Mouser Electronics. Tjhe part number is below. I cannot see anything on the switch terminals labels like "supply/earth/load" As a result, I cannot tell which is which. When you say, "connect all the Earth terminals together and use one 1N4003 diode to supply common, the U or outside rail terminal." Do you mean all the commons from all of the various track circuits all together? I just don't understand how I would do that and where the diode would go and so on . . . .
Mouser Part #:540-RRA22H3BBRLNManufacturer Part #:RRA22H3BBRLN
Manufacturer:
Ok. First of all, if you had bought LED lighted switches, I meant that you only needed to connect all the lamp pins of the switch together, then to the diode 1N4003 anode side (the arrow) and then the cathode side (the bar or line) of that diode to track common. Only one connection to the track common from that diode, the other side of which goes to all the switch tabs labeled Earth. But that is for automotive switches.
BUT...you bought non-automotive spst switches with a 125 VAC bulb circuit in it. So the track voltage of 18 VAC is not enough to light that bulb.
If you still want to pursue the Mouser switches that you bought, you could buy the part #
540-RRA22H3BBRHN
The H as the second to last character is for the switch with the 12 VDC bulb. In that case, with this different switch, you connect all the #2 lug of all the switches together and connect that to the 18 VAC track power (A on the transformer). You connect the #1 lug of each switch to the block power load you want to power with the switch (the center rail of each block to its appropriate switch). Then for the lighting, you connect all the #3 switch lug to a single diode anode. Then connect the other side of the diode, the cathode, to track common (the outside rail or U of the transformer). Since you are using bulbs, and they consume more power, each switch should probably have it's own 1N4003 diode to common.
These switches are, or should be, labeled as to which lug is what. It's probably embossed in the plastic next to the lug. I do not see the pin numbers spelled out on the datasheet.
If it were me, I would go to the auto store and get the lighted automotive switches with the LEDs in them instead of these with bulbs. Calterm is one brand that is popular. Oval switch but mounts in a round hole.
But either will work, you just have to have more diodes to handle the bulb current.
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CJack and everyone,
I do thank you all for your expertise. There are some roads better not taken.
eliot
stan2004 posted:... in our quirky O-gauge block powering we can get this situation (albeit rare and should not happen): An engine or lighted caboose momentarily straddles (because of the two center-rail rollers) the powered track and the un-powered siding. In other words someone drove an engine into, or backed up a consist with lighted caboose into an unpowered siding (the toggle switch is OFF). ...
Stan, this is exactly how I discovered my problem with these type of switches. The switches I have had been installed for months, maybe even a year or more, and working with absolutely no problems at all (or so I thought). Then one day I ran an engine into an un-powered siding and the breaker tripped.
Since the switches had been working for quite some time I was stumped. I checked everything but the switches. Anyway, it took a while, but turned out the switches were the problem. That's when I added the relays, which seemed like the easiest fix at the time and I already had a bunch of relays in stock.
I guess this doesn't help Scrapiron here, due to all the extra wiring, but the switches with the LEDs do work well after you add the relays. I would offer to help him wire it up if I lived nearby.
I'm not sure what y'alls issue is, but SPST LED lighed swiches work fine and now for almost 10 years. No relays are necessary and they would not help if the wiring were to include pitfalls. With an SPST switch or appropriate wiring with an SPDT switch, if a car straddles the block and mainline, it just powers the block across the open switch. I don't know how the caveat with the spdt switches would be wired for failure under certain conditions, but I would not use the NC contact if I had used them.
Chuck,
I have about 20 that, if you hook up the earth terminal to light the light, they result in a direct short when bridged by a pair of rollers on a siding that is not turned on.
If you have a schematic of how that's wired I would be interested.
Mine do the same as John H's. Mine were wired the same as shown in your drawing above. Terminals are marked Supply, Load and Earth. I got them on ebay from one of the Asian suppliers a couple of years or so ago.
With the switch in the off position, mine have continuity between 'Load' and 'Earth' causing the short when bridged by pick up rollers from main to siding when the siding is off. When the sidings are switched on everything works just fine, no shorting anywhere.
As I said above, I didn't notice the problem for somewhere around a year or so. I had a switch set wrong and the engine went into the un-powered siding and immediately shorted and power went off. The switches were the last thing I suspected since they had been in service for so long, thought something else was wrong.
To power both a light and a track, you really need DPST switches. Two poles, no shorting... 
OGR Webmaster posted:To power both a light and a track, you really need DPST switches. Two poles, no shorting...
That's ideal, dpst. But these automotive switches have the NO terminal connected to a resistor in series with an LED to common. And that NO terminal is also connected to the load (center rail) which also goes to common thru the engine or car. So it's like having a resistor plus LED (series and a 12vdc rating) in parallel with an engine from center rail to common. Remember that 18vac rectified by a diode (the LED) results in effectively 12 vdc. What I was trying to say was that having a pair of rollers short across the pole and the NO terminal or just having the switch close is the same thing.
So these auto switches are great for the block switch but you do, or should, put the LED circuit to common thru a diode to protect the LED from the reverse cycle of the 18 vac. That may be the problem that rtr had surface after it worked for so long. Mine have been working for 10 years and I've run engines across open switches routinely.
The diode was in place on the common. That was not the problem in my case. It is the switches themselves. They have continuity between the Load and Earth when the switch is in the Off position. Brand new switches right out of the box.
As rtr12 (and others) are saying, some/many 12V automotive illuminated switches behave like SPDT switches in the "OFF" position by shorting the LOAD and EARTH terminals (which of course also extinguishes the lamp/LED).
Left case: Turn switch "ON". Hot is applied to the siding center rail via the LOAD terminal. The lamp/LED (between LOAD and EARTH) lights up. All is fine.
Right case: Turn switch "OFF". LOAD and EARTH are shorted by switch. Then an engine or caboose straddles the main and siding center rails. Hot is fed into the LOAD terminal and right over to the EARTH terminal. The 1N4003 diode in your example now gets full track voltage and out comes the magic smoke.
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Too bad the magic only happens once. 
rtr12 posted:The diode was in place on the common. That was not the problem in my case. It is the switches themselves. They have continuity between the Load and Earth when the switch is in the Off position. Brand new switches right out of the box.
Oh, sorry I didn't get it at first. Didn't expect that to happen as I thought the switches all were purely spst. That shorting action makes it an spdt with an LED-resistor across the NC side. Thanks.
gunrunnerjohn posted:Too bad the magic only happens once.
In ham radio, the smoke is what makes the thing work. If the smoke escapes, the thing becomes dead...by actual observation.
Trust me Chuck, it works the same way with a vast majority of electronic devices! 
By actual observation multiple times! 
Holy smoke...(no pun intended, sort of). I just tested one of my switches and it surely is an spdt as you all said it might be. I wonder why I never smoked anything because I have run off onto the block. Maybe the engine ran until it stopped and was going at a fast enough rate that it didn't have time to heat the short.
I appreciate the patient answers and tenacity until I finally got it. Something new to worry about, or looking at it differently, something to think about.
gunrunnerjohn posted:Too bad the magic only happens once.
That's why I always order multiple quantities!
P.S. They really should give us at least one Mulligan on these things. (Or whatever those extra, do over golf shots are called?)
cjack posted:Holy smoke...(no pun intended, sort of). I just tested one of my switches and it surely is an spdt as you all said it might be. I wonder why I never smoked anything because I have run off onto the block. Maybe the engine ran until it stopped and was going at a fast enough rate that it didn't have time to heat the short.
I appreciate the patient answers and tenacity until I finally got it. Something new to worry about, or looking at it differently, something to think about.
I never smoked anything either and the switches are all still working just fine, but now there are relays added and the shorting has been eliminated. It took me a a couple of weeks, maybe longer, to figure out what the problem was. I actually don't remember how I stumbled across the switch being the problem, but glad I finally did, it was driving me nuts even though by leaving everything on there was no problem.
Stan's pictures are worth a thousand words! And I thank him for the illustrations above, that makes it all much clearer, and it helps me too. He is also very good at explaining things, much better than I am that's for sure. Wish I could have had him come over here when I first discovered the problem. If I wasn't so old I would hire on as Stan & GRJ's apprentice. 
stan2004 posted:As rtr12 (and others) are saying, some/many 12V automotive illuminated switches behave like SPDT switches in the "OFF" position by shorting the LOAD and EARTH terminals (which of course also extinguishes the lamp/LED).
Left case: Turn switch "ON". Hot is applied to the siding center rail via the LOAD terminal. The lamp/LED (between LOAD and EARTH) lights up. All is fine.
Right case: Turn switch "OFF". LOAD and EARTH are shorted by switch. Then an engine or caboose straddles the main and siding center rails. Hot is fed into the LOAD terminal and right over to the EARTH terminal. The 1N4003 diode in your example now gets full track voltage and out comes the magic smoke.
Thank You Stan!!! Your illustrations are really quite helpful.
I like the Marvel Comic red explosion. Might need a BLAM next to it.
Chuck,
Remember this thread? Seemed like everybody thought I was nuts. I'm glad to finally get the problem figured out.This forum has been responsible for a big part of my train knowledge since starting up 10 years ago. And today I learned the mechanism of magic smoke. BLAM!
You might have noticed in another thread GRJ used "silicon puddle" to describe what happens when you over-voltage an LED. Someone educate me; if you blow up a silicon diode you get magic smoke, but if you blow up a light-emitting diode and you get a silicon puddle? 
John H posted:Chuck,
Remember this thread? Seemed like everybody thought I was nuts. I'm glad to finally get the problem figured out.This forum has been responsible for a big part of my train knowledge since starting up 10 years ago. And today I learned the mechanism of magic smoke. BLAM!
My switches look just like yours, but I got them from an Asian supplier, not in the US. How did you fix yours?
The inexpensive relays fixed me right up? Well the relays and a little re-wiring that is. I do like the looks of the switches and their LEDs. The relays don't add a lot to the cost so I am planning to continue using them. Plus I have at least a dozen still unused, I really do always order extras of these things.
