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Scale Rails of SW Florida Trainroom

DCC Power Management
We currently use PSX and PSX-AR for circuit breaker protection and reversing loop control in our 49 power districts.

Background: Our club moved from relay type products to PSX electronic products for circuit breaker protection of our 49 power districts in 2009. At the time we added a Sonalert type device to each PSX board so it would make a noise when a short occurred. Two lessons: Not all of our members could hear the high pitch Sonalert device (Sonalert brand is very expensive, others are available). 2. You could not localize the tone with a full room of engineers during Operating Sessions. The result was a needle in a hay stack. The PSX products are distributed around the layout in 14 clusters between two levels plus staging.

We tend to have more shorts that some clubs because we use all electro-frog turnouts with powered frogs. So most shorts are the front trucks of the loco hitting the frog with the turnout set the wrong way. It causes a short before it derails.

Scale Rails uses PSX electronic circuit breakers from DCC Speciality for block power management.

Scale Rails uses PSX-AR electronic reversing loop controllers from DCC Speciality to automate reversing blocks.

Issue: How to find the short.
Solution: Central Power Status Dispays

Add Red LEDs for local and central display of shorts. Local display required 3-4 LEDs near the PSX products. Central display meant two locations where all power district LEDs would display. We built the two central panels with 60 LEDs (11 for growth). Next pictures you see the local and central displays. The green LED is a power light.

Local Status Dispaly

Central Status Display - First

Summit has a short.

No one uses the Local Displays once the Central Displays were completed.
Central Status Display - Second

Mirror of the other Central Display.
Architecture: The PSX product drives a Opto-isolator IC and in turn drives a Transistor that in turn drives the three LED’s per PSX circuit (one local and two central). This is very basic. Parts are cheap ($2 per circuit). Most clubs will have parts around. We chose not to build a multiplexed system, instead we use wire to interconnect the large panels. We happened to have 48 pair phone cable around. This needs to be something other members can maintain.

Design: You say why not drive the LED’s from the PSX directly. Well, the board comes with a built in resistor to drive one LED, so three would not work. Second, (not happy about this) the PSX and the PSX-AR have a different common wire voltage. This meant the un-switched terminal on one is GND and on the other is +5V. This means they cannot share a common ground. We decided to use a opto-isolator IC to address this problem and protect the PSX boards. We used a 2N3904 NPN transistor to drive the three LED’s in the status displays. You can use whatever you have in stock. The 2N3904 is a work horse (150ma) and cheap.


The Power Supply needs to handle 30ma per circuit. We used 5VDC at 500ma. You also get another bonus, the PSX-AR LED will flash when it's reversed. Both the PSX and PSX-AR are on solid when shorted. We added a two pin terminal to the PSX boards to avoid soldering wires and make changing easy. Less chance of damage.   The connector goes on the Remote Status connections. PSX J5 Pins 1-2. PSX-AR J5 Pins 3-4. Not the same.

Construction: We used proto-board for each of the 14 circuit boards. We built them all identical except for the number of circuits. Pictures are included. Each LED needs a resistor, remember you cannot put LEDs in parallel. All the parts come from Jameco. Below is the parts list. Be careful if you use small solid copper wire, it can break easily. Once installed it reliable. Parts List per circuit:

-          15K resistor or watt ($0.04)

-          470 resistor or watt ($0.04)

-          2N3904 transistor ($0.06) (178597)

-          H11A1 or equivalent ($0.29) (878286)

-          Connectors – euro style ($1.15 for 12 connections) (215011)

-          LED’s (red) (3) ($0.24)

-          5VDC 500ma wall wart (one for project)

-          Buzzer ($2.95)(1956696)

-          2 pin terminal ($.39) (2094506)

-          6 pin IC socket ($0.13)(683091)

The H11A1 does one circuit.

The Buzzer for each PSX product is 1956696, prices have gone up ($1.25-2.95). The PSX puts out 5VDC max. You may need to bend the leads to fit the holes in the board. You will want the buzzer.

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