Good news is...that DCC users also can use the circuit below and can neglect needing to add the choke as that was for DCS only. If you want to use a different amount of LEDs, a good calculator that was used to figure out the original resistance is here: http://led.linear1.org/led.wiz For your source voltage, just take your AC voltage (I design for higher voltages just in case) and multiply it by 1.41. Then hopefully you already know what LEDs you are buying or have and can input their characteristics followed by how many you're using and presto...it tells you what resistance you need and what wattage. This could be handy if you want to adapt the schematic below to light say...3 LEDs for a caboose.
I went ahead and did a car or two to show my dad what the steps were and what a finished car looks like and how to copy it as I will leave the rest of the fleet for him to do.
I figured I'd share with the rest of you guys as well. Again, a big thanks for helping with the schematics goes to Dale H and Dale M of the OGR Forum. As always, click on the pictures to see a blown up version of it so you can study them and/or ready the diagrams.
Note that there are 2 methods. Since we're using half-wave rectifying from AC to DC in each method, it is important that half the cars in the train use method1 and the other half use method2. The difference between the two is the orientation of 3 types of parts. This means that every 2 cars should use the full wave of the AC signal and leave relatively close to 0 DC offset, which could cause horns or other various sounds, etc. to go off that base their selections off a certain voltage. If one would rather not be worried about the offset, they can purchase full bridge rectifiers instead and replace the diodes with them. Also putting in a ceramic fuse would be another option if going that route for extra circuit security.
Note that the pictures below follow method 2. For method 2, I basically handwrote the +/- conventions for method1, but knew to flip the components as necessary (+ on -, diodes down, etc.)
Above is a picture of what the various components look like. I made a mistake and the choke is actually 22uH not 22mH...22mH would be massive (yes I own some of those too). Nothing too intimidating here except maybe the LED, which is harder to see the polarity than the other components. Note the Diode and Cap both have indications on the components themselves to show polarity. The LED does have a sharp corner to help, but you definitely need a diagram to know whats what when you first start out. The resistors and choke are not polarity sensitive - you can put them in any direction you like.
Above is the original connector that goes to the lighting board. The black piece fits into the bottom of the interior and has springs that make connections to flat plates on the underframe piece. Take the red wire and cut out a piece of wire and add in the resistor and the choke in series. Below is the result with clear heatshrink tubing.
Above shows the interior with the original MTH lighting board lined up where it would go if they were inserted into the Amfleet shell. I have marked off 5 locations for the LEDs as well as where the +/- inputs are.
The above photo shows that I used the original crossings in the metal strips for the LEDs. The LEDs fit snugly onto the 2 prongs that come across the gap that the original MTH lights used. I did have to use copper wire to move the light on the furthest left closer to be inside the interior. Below is the other side that actually faces into the car. The cap is at the end past the "bathrooms" and cannot be seen.
The above photo shows how I knew I had an error I had by not cutting a particular route on the Lighting board.
Above is the underframe piece as originally built. I basically traced the 2 wires that led to the pickup rollers and desoldered these wires from the trace on the underframe. Because this car was part of a 2-car set that had end lights in them with their own circuit, I also desoldered the wire that lead to the switch. I soldered in series the diodes from the pickups to the trace. I soldered the lead to the end-lights switch at the pickup roller end of the diode so it wouldn't go through a second diode. Result is below.
I just wanted to take a picture of the end with the end-light circuitry for reference. It has its own diode.
Above and below are pictures of an amfleet with the original incandescent lights.
I had to angle the camera relatively high to actually see one of the LEDs. They are not invasive at least in these cars.
The last photo is just to show that the end lights still work.
Perhaps the most amazing part of this venture was the cost to do one car not including items like solder or heat shrink tubing...
Total cost for parts above (when ordered in bulk, parts had free shipping off eBay):
-diodes(2): .02*2
-choke: .10
-resistors(2): .03*2
-capacitor: .25
-LEDs(5): .10*5
TOTAL: $0.95 per car + ~1 hour of your time
Hope this helps you guys out there on the fence about converting your cars, but not able to afford $15-$35 boards to retrofit them.
No comments:
Post a Comment