Electromagnetic Uncoupling That Works!
#16
Thanks, Gary. I think 24 volts in series would work best for me. We have a requirement on all modules to have a UL approved 110 volt set of plugs in a junction box mounted to the module, and we connect the 110 volts from module to module around every set up so that if something needs to be soldered on a module during a show, we have 110 volts available close by. I'll just look for a suitable transformer with enough capacity to do the job if I build a test piece to try out.
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#17
Russ, I've been using 24 volts DC. Being an electrician and a model railroader, "transformer" can mean two different things - electrically, it is a device that converts one level of AC voltage to another level of AC voltage. With MR, it converts AC to a lower level of DC. I think the magnets will work on either AC or DC, but to get the same effect from AC as with pure DC, the voltage would need to be around 33 volts or so. So anyway, which transformer are you considering?

Edit: Senior moment discovered! Concerning power, 24 volt RMS AC is equivalent to 24 volt DC. DOH! :x
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#18
I was using "transformer" in the "electrician's" vernacular. Stepping down 110v ac to 24v ac. I would need to check an electrical supply house or Grainger's to see what is available. I'm thinking I need something made for an industrial application. The only homeowners applications I can think of now are door bells and heater/ac controls, and I don't think either of those is designed for the amount of power I would need.
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#19
Edit: I had a senior moment. 24 volt RMS AC is equivalent power-wise to 24 volt DC. Doh! If you can find a 120-24 volt xfmr with the proper capacity, you will be okay.

Now, if you are thinking about DC, you may find a PS as cheap as a 24 volt xfmr. I found a neat little 24 volt DC 2.5 amp power supply for $39:

<!-- m --><a class="postlink" href="http://www.trcelectronics.com/Phihong/psaa60w-240.shtml">http://www.trcelectronics.com/Phihong/psaa60w-240.shtml</a><!-- m -->

Another for $37, Din rail mount, 2.5 amps - very neat! - Would go great inside a control cabinet.

<!-- m --><a class="postlink" href="http://www.trcelectronics.com/Meanwell/mdr-60-24.shtml">http://www.trcelectronics.com/Meanwell/mdr-60-24.shtml</a><!-- m -->

Another little unit, $32. PST-AC2425 2.5 amps

<!-- m --><a class="postlink" href="http://www.powerstream.com/ac-2420.htm">http://www.powerstream.com/ac-2420.htm</a><!-- m -->

There may even be some cheaper ones too. This was just a quick search on google.
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#20
For what it is worth, here is a schematic of the uncoupler control circuit.

It contains circuitry to allow only one magnet to be energized at any given time. The purpose of this is to prevent overloading the power supply. For example, say we have a 24 vdc 2 amp supply. Each magnet will draw 1.5 amps. If two magnets were turned on at the same time, we would overload the supply with 3 amps. The Master Relay and its associated normally-closed contact control this.

The purpose of the On-Delay Timer and its associated normally-closed contact is to turn the magnet off after 5 seconds.

Note that the Timer and the Master Relay are located at the Control Cabinet. All we need is one of each regardless of how many electromagnets we have.

At each magnet location, we have a momentary pushbutton and a control relay with two contacts. The relay is used to "latch" the magnet on when the button is pushed, allowing the magnet to remain energized when the button is released. The On Delay Timer will turn the magnet off after 5 seconds as mentioned above.

The vertical colored lines (red, blue, brown, black) represent the "bus" wiring which extends to each magnet location. I used these particular colors because 4-conductor 18 gauge cable with red-blue-brown-black wires is readily available.

Note: Regardless of the number of magnets, all we need is four wires coming from the control panel. Again, it is these same four wires which connect to every magnet location. A single 4-conductor cable is routed under the benchwork, and each magnet is tied into those wires as shown.

Although I am showing only two magnet locations, we could add as many as we want simply by repeating the magnet location circuitry and connecting them to the 4 conductor bus. This is indicated by the arrows at the bottom of the schematic.

Edit: It isn't shown on the drawing, but I am using pushbuttons with a clear red cap. Installed an LED in it, so the button lights up when the magnet is energized. The LED and resistor is connected between the orange and black wires.

<!-- e --><a href="mailto:jringreatwhitenorth@yahoo.com">jringreatwhitenorth@yahoo.com</a><!-- e -->


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#21
Thanks Gary. I've saved the schematic in my "Train Stuff" folder in My Documents.
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#22
Russ, that is the circuit I am using which doesn't have the "repeated on" protection. Yesterday I figured out a simple circuit with two on delay timers that would accomplish your "5 seconds on, 30 seconds off" suggestion. I can draw it up and post it if you would like.

If you used the e-magnets, how many would you have on the module? Reason I ask is that if it is only one, the circuits can be simplified.
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#23
Russ, I had a moment of insight... it would be a simple matter to install an "off delay" relay at the control panel (in addition to the existing "on-delay" and Master Relay) to incorporate the "anti-re-energization" circuitry. There would have to be a few wiring changes at the control panel, but the field wiring stays the same.
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#24
When I get time to build a test module, I will use a non delayed "E-mag" to see if it pulls the cars too much. I have probably 50-60 kits from various manufacturers to build in my garage. Included are probably 40 "shake the box" kits from Athearn and ConCor. since the Athearns can be snapped together without glue, I can experiment with various methods of adding weight to the Athearn cars and snap them together for test purposes. If I find that the "E-mag" pulls the cars too much for reliable uncoupling operation, then I need go no further with the build.
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#25
I hope I am wrong, but I am betting the steel weights will cause too many problems. Sad
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#26
Thanks Gary, that wiring diagram is just the Duck's nuts. Thumbsup
I think it will clear the mental block I was having,... once I can study it a bit.


Jack 219
LIFE....
..... Abandon the search for truth
Look for a good fantasy
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#27
Jack, here is a photo of the control relay and pushbutton that go at each magnet location. I mounted the relay on din rail along with terminal blocks to ease the installation. The terminal blocks aren't necessary, all the wiring connections could just be soldered and insulated.

From left to right on the terminals, the first black and orange are for the magnet, the next black-orange-blue are for the pushbutton and LED, and the last four terminals, black-red-blue-brown are for the electromagnet circuit "bus" wiring which extends around the length of the layout.

[Image: image.php?album_id=138&image_id=2392]
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