Bob
Remind me what the advantage of the capacitive discharge setup. Is it just so the switch can be thrown w/o track power or also to prevent switch burnout if a train is parked on it?
Bob
I hope you haven’t ordered anything yet. Since you’re going with the DC capacitive discharge scheme, the latching relay should be the 12-volt model, not the 5-volt. And, because it is a polarized relay, the positive side of the capacitor should be connected to the outside rails, not the negative. Although they don’t call it by that name, you can get the number-53 lamp (and sockets for it) at Radio Shack: http://www.radioshack.com/product/index.jsp?productId=2103782 Note that we are not using the lamp as an indicator, but as a resistor to charge the capacitor. I don’t see any momentary SPDT toggle switches in the Radio Shack catalog. They do carry this DPDT: http://www.radioshack.com/product/index.jsp?productId=2062530&filterName=Type&filterValue=DPDT I think a miniature switch would be a better fit for your panel; but you’ll have to order that.
Bob,
I ordered one latching relay. This is the one I ordered. Is this correct. 769-DS1E-ML2-DC12V
2A 12VDC SPDT? If not that is OK I only ordered one to try my hand at switch modification. If this all works I can do the rest. I’ll be stopping at Radio Shack for the capacitor, switch, #53 lamp and the red and green LED indicator lamps.
Bob,
I found this switch http://www.mpja.com/prodinfo.asp?number=5009+SW
What do you think of this one?
That looks perfect.
Bob, I am thinking these red and green indicator lights will work on my panel. They are 12 volt. What do you think. Sorry to keep bothering you, but once I find all the parts I can get started.
Yes, they will work fine. You could also buy naked LEDs and add your own ballast resistors, but those will save you that trouble. It looks like they will each occupy about a 1/4-inch-diameter circle on the panel. Is that small enough?
I think these will work. Since I haven’t built the control panel I can make sure they will work. Couple more things to round up then I can make my first one and see how it works.
(Submm) Bob, I see that I didn’t answer your questions. The answers are “yes” and “yes”, but they are related. You can modify an 1122 or 5121 just for constant voltage; but then you run the increased risk of burnout. The capacitive-discharge circuit protects you from that; so it’s a good idea to do both.
I say “increased risk”, because you can also burn an unmodified turnout up if you park a train on it with the track voltage turned up. It’s just less likely that you would do so.
Bob,
I am rounding up the parts I need to convert one switch.
I have
1 electrolytic capacitor about 4700 or 5000 microfarads 4700 uF 35V 20% Axial-Lead
1 14.4V 120mA Incandescent Flashlight Bulb bayonet base - I also got a socket so I can change out the bulb if it burns out and so I won’t have to solder d
You’re right about SPDT instead of SPST. I have edited that error out.
Because we’re using the capacitive discharge circuit, we must use DC to power the turnout. All it is is the electrolytic capacitor charged to about 16 volts (or whatever it takes to throw the turnout, probably more than 12) powering the turnout coils and the latching relay coils (which will be wired in parallel with the turnout coils). When you throw the turnout, you get voltage from the capacitor for a short time, until it discharges. That is what protects the turnout coils from burning out. There is no harm in giving the relay a little extra voltage for such a short time, even though it is rated at 12 volts.
You can make your own DC supply if you want from a small train transformer. This is very simple to do and would give you the ability to adjust the voltage if you need to. This requires a bridge rectifier and another electrolytic capacitor. The only thing you will need 12 volts DC for is the LEDs, which will be controlled through the relay contacts; so that can be a separate HO-type power supply.
The first step will be rewiring the turnout.
I got the LEDs today. They are wonderful. Very small. I will only need about a 3/16" hole in my panel for them. If anyone needs LEDs in red, green or yellow check out these:
Bob,
I got my SPDT momentary toggle swithces to day. I think they will work very well and are pretty small.
We have gone back and forth on the turnout modification so I just want to be sure I have it right before I start on that part of the project. Below is what I have. Let me know if this is correct.
Modifying the turnout: Take off the switch-machine cover and drill out the rivets that hold the plastic top to the steel bottom. There are two rivets on the switch machine, but only one
It’s a good thing you posted that. It should read, “The other side of the lamp is connected to a 16-volt (approximately) DC supply, whose positive side is returned to the outside rails.” I thought I had swapped all the "positive"s and "negative"s earlier; but I missed that one. By the way, do you think the Tyco will put out enough voltage? You need a good 16 volts.
You don’t need diodes for the indicators if you run them from one of the DC supplies, set to 12 volts.
Bob,
Thanks for clearing that up. Here is the listing for the transformer. It says it has an 18 V DC output. Do you think this will do the job?
Yes. It looks promising.
I just went through a bunch of 1122s and manual equivalents. All of them had bad electrical connections. Some looked like they had been wet, and some were pristine. It didn’t matter. They all had loose electrical connections. I recommend you solder all the connections before you reassemble the switches. Work quickly because the plastic does melt a little. The rivet in the center of the fat center rail needs to be soldered at both ends. I used a 4-40 screw for the frog with a pan head screw which fits nicely into the depression in the bottom cover plate. When you drill and tap the hole, use a little WD-40 for cutting oil, and it will drill and tap much easier. I also replaced the ground terminal because I am not adding Bob’s cap discharge modification. To do this, I polished the metal tab that sticks out of the motor housing and also polished the area of the stud that would be soldered. Then I soldered the stud to the metal tab. Then here is the tricky part. I put a thumb nut onto the stud and used a pair of channel locks to hold the stud tightly into the bottom cover plate. The channel lock jaws are slightly offset so I could have one jaw on the thumb nut and the other on the bottom cover without covering up the hole where I was going to solder. Then holding the channel locks in one hand and the soldering gun in the other and having the solder draped over the edge of the table, I was able to do this 3 handed operation by myself. You can check your work by making sure the cover is held tightly by the soldered terminal. I also soldered two of the tabs that hold the outside rails in place to make a good connection between the outside rails. I had one switch that had the ground terminal broken off and it was lost. I soldered a 4-36 pan head screw to the bottom cover and made a new terminal. The thumb nut holds it tight to the metal tab coming out of the switch motor. Bruce Baker
I got both the transformers for 99 cents. I’ll check them out when I get them. They also have an AC output so I might be able to power some small accessories or lights with them.
Bob,
OK I got the turnout apart with no damage. My question is: Do I need two capacitors, one for each of the two wires from the coils? Should I run the wires that I attached to the coil wires all the way to the control panel and attach them to the capacitors or should I locate the capacitors below the table at each turnout?
I should have my DC transformer in a few days and we can start working on wiring the toggle switches and latching relays. I am taking pictures of every step of the procedures so I can document the process. I’ll post them here once I have one complete working new turnout.
The two wires, one from each coil, which were connected to the center rail inside the turnout remain connected to each other after you disconnect them from the center rail and both get connected to the negative terminal of a single electrolytic capacitor associated with that turnout. I locate mine under the table at the turnout, since both its connections are handy there; but you could put it wherever is convenient for you.
Have you been able to identify the negative capacitor terminal? The minus-sign symbols are often inside circles which are themselves inside a stripe with an arrowhead pointing at the terminal.