Requesting help for an appropriately sized Power Supply.....

We need to know how much current is drawn by holding the coil in the relay to the open position when you want to disconnect power to a block, I think.

If I did my back of the envelope calculation for the LED and resistor draw (approx 21 milliamps each circuit, I think), that would be roughly 1/2 amp if you had 25 circuits simultaneously.

So you have one amp left for however many relays you wish to activate in order to open the circuit and kill the track power.  You gain the small amount (21 mA) for each one since the LED won't be lit anymore, but you need to have enough current to continually hold the total number of relays open.

As an example (not your type of relay in terms of contacts, but so you can see the math), this relay says it uses 66.7 mA for coil activation.  10 of those at one time would take you past half an amp.

How many tracks would you ever remove the power at one time?

There are all sorts of options for 12 V supplies.  I'm sure others will suggest.   The simplest thing may be to just buy a second one of whatever you have and split the 25 tracks across the 2 supplies if you were not having problems before.  Then again if your habits of how many you may activate at once may change, you might benefit from completing the actual calculations.

What you say about the random turn on when you would power more blocks off probably makes sense since the lack of current capacity would probably cause some of the relays trying to hold the open position to revert to closed, therefore re-powering the track.

-Dave

The 12 volts is only used for the LED until the toggle switch turns off power to the track. You must be using a DPDT relay.

So the only thing that requires current is the electromagnet in the relays. If your supply can go up to 1.5 amps and we divide by 17 (the last block before the trouble started) that's 1500ma / 17 = 88ma per block.

You have 25 blocks so that comes to 88 * 25 = 2200ma total. And including a generous fudge factor, you need a 3 amp 12 volt power supply.

You can find these on EBay with a search like:

12v 3a power supply

Here's an American supplier with excellent ratings that has them for under 7 dollars.

Good luck!

  -- Leo

 The relay coil and circuit specs are usually grouped logically, and listed on the relay cover.  Maker and part# will get you spec sheets too.

   Find the coil voltage and amp/ma draw, and multiply amps by 25 circuits, add the total l.e.d. draw, and add about 20% for continuous feed/heat build, etc, and you should have the amp mininum required for a cool running, unstrained supply even when you throw every switch at once and leave them.   If you know for sure you will use less toggles than 25 thrown at one time, you can choose a smaller supply, based on the max toggles that you will use at one moment 

Hello Dave, Leo and Adrian!

Thank you all for the quick responses!

To answer your questions, I'm using the LY2N series DPDT relays. According to the specs sheet I found on these, the coils are rated at a 75 mA current draw and a resistance of 160 ohms (which is a bit different from what Dave found).

As far as how many relays would be energized at one time.....worst case is 24 out of 25. I say that because my layout uses MTH DCS and I don't have a separate isolated track where I can "add" an engine to the TIU. So I "shut off" all the Power Blocks except one to add the new engine. That way I can park existing trains on any Power Block and kill the power to them anywhere on my layout.

For the LEDs, there are 2 mA ratings. One is "Peak DC Forward Current" rated at 100 mA. The other is "Max DC Forward Current" rated at 30 mA. Don't know which one should be used....

Did I mention OGRR Forum Subscribers are the BEST?! You are!

 

As was said above it looks like you should be using around a 3 amp PS to do the job.

Maybe it's just me but I am having trouble getting my head around why you are wiring them up so that the relay needs to be energized to unpower the block? Using this scenario your fail safe state is power on to the block if anything in your hookup or power system fails. That could be bad for any number of reasons. Suppose your PS for your relays suddenly fails; boom, all your blocks are 100% energized suddenly without warning.

Why not wire them so that when energized the NO points are closed and power flows to the block in question, and stays in this state until you power the relay down? Most relays are designed for 100% duty cycle, so its not like you risk burning them out. What am I missing here?

Rod

I failed to mention that the EBay listing that I posted earlier was the first one I came across. They also have 12 volt power supplies that can handle up to 5 amps and still for less than 7 dollars. And the shipping is free.

There is no danger in going for more amps from a power supply. The current is drawn from the unit by the load as needed. The rest will be kept in reserve for future expansion.

Just out of curiosity, how do you have your wiring set up? Please share what you're experience has been with this arrangement.

Rod has a point. Unless you maybe you expect the blocks to remain powered more often than not, the reversing of the relays might be better. Without actually looking there Leo's 5a find seems pretty prudent. The led question amps to add; the resistor would actually be the limiting factor for passing x amps at x volt. I never really memorized all the basic formulas, I reference them each time. Stops mistakes anyhow. Resistors are one of the simplest though. I'm hoping someone more recently schooled will list it soon.... or it comes up in a search easy for you .. but I need to eat & rest a bit now, my bloodsugar is all over the place...fog-brain is creeping in. The peak fwd is the max before burn out. Usually limits life if even close. The max fwd is the max to light it up . The resistor is limiting what the led gets. So the amps passed by the resistor at x volts is the number you need x25 (the math is easier at 25 than 24 and adds wiggle room ).

The LEDs draw about 20 ma the way they’re wired, so figure 25. That’s about 100 ma total for each relay ckt. Or 2.5 amps total for the whole bunch. A 3 amp or more supply is required.

Wow...this is great! Lots of great responses! I will try to answer questions in the order they were posted....

Rod and Adrian - I chose to have the relays default to Normally Closed (NC) for 5 reasons....1) I use DCS and I had a heck of a time getting a consistently good signal strength on all my routes. Plus I was doing signal strength testing well before the control panel was built and it made sense to me to have all the relays for the Power Blocks in place in the event the relays were causing signal strength issues. 2) In my case energizing the relays is the exception not the rule. Like I mentioned earlier I don't  have a dedicated section of track segregated from the rest of the layout to add engines to DCS. Having switchable Power Blocks allows me to do that easily anywhere on my layout. 3) My layout is 12 x 18 feet. There have been instances where crashes required me to crawl under and on top of the layout to retrieve derailed engines and cars. I did not want to do that or have to remove existing engines every time I wanted to add an engine to DCS. 4) I can run engines even if I had a catastrophic failure with the relay circuits (like every time I have visitors and they want to see trains run. Anybody ever have that happen?). 5 ) When I do/did have wrecks, it is almost guaranteed my TIU would get scrambled causing me to do a complete reset and do an add of all engines again (I lost 2 TIUs because of wrecks that I need to send them to either GRJ or GGG to get them repaired. This is with several TVS' in place and 7 A circuit breakers on all the main track power feeds.....but I digress).

Dave - did I mention I loved your "back of the envelope" imagery. Been there and done that as well!

Leo - Thanks for all the Power Supply recommendations....I will check them out today. In regard to your questions about "how I have my wiring set up". I'm more than happy to share...just not sure what you're asking/wanting to see. Please let me know. As far as my experience with relays controlling the Power Blocks....it's worked really well for me. But I must tell you I have gone through a SERIOUS amount of 18-3 wire to connect all these relays to the control panel!!

CJACK - Thanks for chiming in. With all the great recommendations, I'm already planning on going with at least a 5A Power Supply because I have plans ( that I've not shared with my Wife yet ) on adding a switch yard.

Phew!

Well, sounds like future expansion is already in the works! Good for you!

I am sure that you must have the relays placed out near the individual blocks with the control wires running back to the control panel. The control wires don't have to carry a lot of current so they can be smaller/thinner (like AWG 20-24). Track power then runs around the layout and is the thick stuff (maybe AWG 12-14) and is accessible to the relays. Still, as you said, that's a lot of wire.

I have something like this that I'm planning to do with a conventional layout and am happy to find that others have done something similar.

Hi Leo......

Now I think I know what you're after! Okay...here goes. The wiring was laid and installed using the star or home run method of wiring. This wiring method is recommend by MTH for carrying the DCS communication signals from the TIU to the engines. This approach works for conventional layouts as well. In fact, I do run conventional trains from time to time. And I believe you wouldn't have to be as strict with your designing in the Power Blocks. DCS suggests Power Blocks consist of approx. 10 track sections/connections per block. Conventional wouldn't need that "restriction".

I use Lionel tubular track. No special reason other than the fact I had a LOT of it. The layout has 4 power distribution points. Why 4 you ask? The TIU has 4 ports and for power I use 4 PW Lionel ZW transformers.

Each distribution point has connections to 6 - 7 Power Blocks. I used 14-2 wire in a sheath (similar to this https://www.amazon.com/AmazonB...eaker+wire&psc=1) for all track power connections; transformer to TIU to distribution points to each Power Block. Wire connections to the track/Power Block itself are soldered. I would cut a 2 - 3 foot "lead" of 14-2 wire, solder one end to the track, drill a hole in the table for the lead, pass it through the table, then connect the relay to the other end of the "lead". I used almost a 500 foot roll of the stuff!

The relays are installed between the track and the distribution points. I used relay sockets so that all the wiring connections are made to screw terminals on the relay socket (I can't imagine trying to make solder connections under the train table on my back). BTW, only the power/center rail needs to be connected to the relay. The common/outer rail connects directly from the distribution point to the track/Power Block. And as I mentioned earlier, I used DPDT relays with one side of the relay contacts controlling the track power and the other controling the LED light on the panel. I used 18-3 wire (https://www.amazon.com/Voltage...8-3+low+voltage+wire) to make all the relay to control panel connections.

Speaking of under table wiring. I bought an auto creeper with a back support. Then I made sure the table was high enough for me to "roll under" the table to do wiring. So much easier than trying to make hundreds of wiring connections on your back! Ah....wiring connections. If you dont have one, get a good crimper and buy lots of spade (some call them fork) crimp-on connectors. You will go through a ton of these!

Now that I built and am using one main control panel; I actually would've done it differently. I was after the old style master control panel look. But with my using the DCS remote, I find myself walking around the layout a lot more than I ever thought I would've. As a result, I would've built several smaller sub-panels (which I plan on doing at some point) for areas where there are a lot of track switches, or where I don't have a clear view from the main control panel. This is something you might think about.

This is a lot of info....hope I haven't overwhelmed you. Let me know if you need more info.

Thanks, Junior! That is a very well done description! I'm completely drawn to the old style master control panel look. I'm thinking along the lines of the CTC machines for routing and dispatching.

As I said, I'm working toward all conventional at this point with lots of blocks and control signals. Also, I have 4 brothers with O-gauge trains that I hope can bring their trains and a transformer to run on the layout. Part of my idea is to keep each transformer with each train. That means switching the transformer power between blocks. Here's a sneak peek at that idea:

The other part involves microprocessor control so that the trains can run unattended if desired. That means slowing and stopping within blocks based on the signal aspects. It will be a mix of the old with the new.

Right now it's all in my head. Everything works beautifully. Nothing ever breaks down, it doesn't cost me anything, and my imagination sits behind the throttle of a 1920 steamer squinting through the sunlight at the upcoming signal.

Hi Guys!

Got my 2nd 12v 10a DC power supply (actually it's a power ADAPTER) today (the 1st power supply was DOA so back it went), hooked it up and.....TADA....all relays and indicator lights (the blue LEDs, the Red/Green LEDs are driven off of the Lionel switches) are working properly.

Thank you all for your assistance!

Hey Junior: That panel looks great! Way to go!

I love it when you've got everything else set up as planned waiting for that final piece to the puzzle and then you plug it in and it all works. You've got this one under control. Or as the British like to say, "Bob's your uncle!"