I would like to wire the loops in my 027 layout for blocks. I think I have an understanding of how to insulate the center and outer rails for this to work. I will be doing the recommended 3 blocks per loop to run two trains on each loop, so I will need three DPDT relays, 3 full wave bridge rectifiers, and 3 signals. I have the signals, but what specifications should I look for when I go to radio shack to buy the relays and bridge rectifiers? I found some that are DC. Will this work on my layout? I thought my layout is AC? (using a modern ZW) The relay I found is rated at 13.2VDC (continuous coil voltage), 9.6VDC pull-in voltage and the contact rating is 5A at 125VAC (resistive). Will this work? What do I need to look for in a full wave bridge rectifier? Perhaps part numbers at radio shack will be very helpful
5A relay should be fine. the trains sholdn’t draw over that. The relay doesn’t draw alot of current so the FWBR does not have to be a high amperage rating. You can actuate a 12 volt relay with a 9volt battery. It will probably only draw about .07 amps at 12 volts. The FWBR is used to convert yiur ac transformer to DC to operate the coil on the relay
Will the second one that I originally posted work that is rated at 14.4VDC (continuous coil voltage), 9.6VDC pull-in Voltage, and the contact rating is 15A at 125VAC? I’m not sure if 15A is too high. Will the relay activate without 15A at a much lower voltage?
Will this work? (I am using a modern ZW with two 180watt bricks and up to 18VAC output)
You’re confusing the coil and the contact ratings. The coils of the relays you mentioned are rated to operate the relay at 12 volts DC. They don’t say what the coil resistance or current is; but if you put 12 volts DC across the coil, the relay will operate and the coil will draw whatever current it is designed to draw, probably not much.
The 5-ampere rating for the first relay is the load current that the contacts can carry. The 240-volt AC and 24-volt DC ratings are for the open-circuit voltage of the load circuit that the contacts can stand to switch. Since your load circuit involves AC at a voltage much less than 240, the relay can handle it. The second relay is rated for a load current of 10 amperes, but no voltage is stated. However, it is very likely that its voltage ratings are similar to the first relay’s.
The outer rail is common to all blocks of your layout so there is no need to insulate it between blocks. Blocks are created by insulating the center rail . A SPDT relay is all you need to energize a block. DC relays are more common. If you use a bridge rectifier across the coil you can energize a DC relay with a ground pulse from an insulated track. If the relay chatters when pulsed use a capacitor.
As for relays, you should use a 10 amp relay in case there is a short and the train derails you would not want to fry the relay. I also recommend you install 7 amp circuit breakers to protect each block from shorts.
There are two outside rails, not one, and one of those two will have to be isolated to create the control rails to operate the relays. He hasn’t said just how he intends to control the trains; but one way involves isolating one outside rail throughout each of the three blocks, to operate each of three relays that open an adjacent section of center rail in the previous block to halt any train that tries to enter an occupied block. In that case only one outside rail is common throughout the loop.
Presumably the second set of relay contacts are for operating the signals that he mentioned.
I have done this for 2 seperate loops. Granted, I did not incorporate signals, but that should not matter. I will try and find some time tonight to take pics of the circuit I built and how I wired it. I think I still have my parts list with Radio Shack part numbers. The circuit I made has a “defeat” switch wired in so I could shut off the relay and just run one train with the flick of a switch. I will also try and post a youtube video of how the trains run on the circuit.
I’m not sure than I understand Mike’s arrangement of control and stop blocks, but I think it might be something like this: The control block precedes the stop block. Train A waits in the stop block until train B, approaching from the rear, enters the control block. This operates the relay, removing power from the loop generally and supplying power to the stop block. Train B therefore stops and train A starts up. As train A leaves the stop block, it supplies power momentarily to the layout generally, causing train B to start and move off the control block. As train B moves off the control block, the relay releases, restoring power to the layout generally and removing it from the stop block. Train A then proceeds around the loop while train B moves into the stop block and stops. Then the process repeats with the roles of the two trains swapped.
Perhaps this is not how Mike’s design works; but the scheme that I just described seems to need some careful tuning of the block locations and the train lengths to work. For example, if train A doesn’t bridge the gap long enough when leaving the stop block, both trains stop. And, if train B is too fast or too close to the rear of train A, it may rear-end it before it stops in the stop block. There are also considerations of what happens when either train has lighted cars with two pickups, that will bridge the gap after the locomotive has departed the stop block.
I think that the scheme that I described in an earlier post is more robust. It keeps any following train from entering an occupied block absolutely. The only restriction on the trains’ makeup is that they be shorter than the shortest block; and that applies only if the number of blocks in the loop is only one more than the number of trains running on the loop. The penalties for this are the need to isolate a complete outside rail for each block and to use a relay for each block.
I’m not sure than I understand Mike’s arrangement of control and stop blocks, but I think it might be something like this: The control block precedes the stop block. Train A waits in the stop block until train B, approaching from the rear, enters the control block. This operates the relay, removing power from the loop generally and supplying power to the stop block. Train B therefore stops and train A starts up. As train A leaves the stop block, it supplies power momentarily to the layout generally, causing train B to start and move off the control block. As train B moves off the control block, the relay releases, restoring power to the layout generally and removing it from the stop block. Train A then proceeds around the loop while train B moves into the stop block and stops. Then the process repeats with the roles of the two trains swapped.
Perhaps this is not how Mike’s design works; but the scheme that I just described seems to need some careful tuning of the block locations and the train lengths to work. For example, if train A doesn’t bridge the gap long enough when leaving the stop block, both trains stop. And, if train B is too fast or too close to the rear of train A, it may rear-end it before it stops in the stop block. There are also considerations of what happens when either train has lighted cars with two pickups, that will bridge the gap after the locomotive has departed the stop block.
I think that the scheme that I described in an earlier post is more robust. It keeps any following train from entering an occupied block absolutely. The only restriction on the trains’ makeup is that they be shorter than the shortest block; and that applies only if the number of blocks in the loop is only one more than the number of trains running on the loop. The penalties for this are the need to isolate a complete outside rail for each block and to use
Thanks for the explanation, Mike. I thought you must be switching power to the center rail outside the stop block, because it is not necessary to have that connection in order to disable the circuit. All you need is to wire the disable switch in parallel with the normally-open relay contact, to simulate the relay’s always being operated. No connection is needed to the normally-closed contact.
My comment about the plus signs still stands. Plus and minus signs are appropriate for DC circuits; but AC voltage, while instantaneously positive or negative, is on the average zero, neither positive nor negative.
Now that I see how your loop works, I realize that it is almost the same scheme that I used in a previous house for an around-the-walls loop above my layout. However, I didn’t use any relays, or electronics at all. Instead of switching the center rail of the stop block on and off, I switched both outside rails (together). So I was able to connect the stop-block outside rails directly to the control rail. I also had a signal at the end of the stop block, with the red lamp between the outside rails and common to show red when the outside rails were disconnected, and the green lamp between the outside rails and the center rail to show green when the outside rails were connected to common by the control rail, again with no electronics except for an extra hidden lamp in parallel with the green, so that only the red would appear lit when the control and stop blocks were unoccupied.
So I just looked at my circuit board and found that I did not wire the +center rail on the control block on either of my loops. I must have realized I did not need the connection, but never scratched it off the schematic.
I think I understand this. I just need to install a capacitor (taking note of polarity) to the relay coil without disconnecting my bridge rectifier. I also bought resistors as I read on a different forum that they need to be used. I don’t understand why I need resistors. Can I return them? Thanks!
I just wanted to say that a capacitor solved my relay chatter problem. I did not install a resistor or diode and I and hope this does not cause any problems. A capacitor will not damage modern locomotive circuit boards? I won’t have to worry about voltage spikes? After much help from folks on this forum and plenty of trial and error, I feel that I now better understand how insulated block sections and relays work. I’m excited to start incorporating Lionel o22 switches into my relay circuits so that I can switch from loop to loop without having train wrecks. I might start a new thread with my block plan and wiring of switches. Thanks so much everyone!
