I have made a small bound into DCC by purchasing the Bachman EZ DCC system, not a bad deal for the system and 3 decoders for under $100. I know DCC has been kicked around a lot here, but I have a question that I don’t think I’ve seen addressed.
I have a couple of FRED’s (EOT devices) that I want to use with this system but they are powered by batteries inside the car. I have seen Ring_Engineering’s EOT device and thought maybe I can rail power my flashers in a similar way that they do it. Actually, I would like some of their EOT’s but $45 plus shipping seems a wee bit too much for something I can make cheaper. I use this circuit (click_here) to animate my EOT. As I said, I power the circuit by using a battery in the freight car, but how would I track power it? I have the mechanical answer to that, I just need some guidance in the electrical part.
Now correct me if I’m wrong, the electrical current running through the rails in a DCC system is AC current. If I want to power my circuit, which needs DC current, how do I connect a rectifier to convert the AC power to DC? or is it ok to power my circuit via the rails without a rectifier?
Concepually, it isn’t too hard. Take the two rails and put them through a bridge recitfier. That will give you DC at track voltage minus about 1.5 Volts. You need to regulate that down to what you need, I think a Zener diode might be the quick and dirty way to do that.
Depends on the circuit itself. I would guess it needs to be rectified. Since DCC is high frequency, a single diode should work to get DC power. Then all you have to do is figure out the voltage of the battery and re-create it with a resistor. Usually batteries of this type are going to be 1.5V. The output of the voltage of the DCC unit will be the final determining factor. What is the Bachmann’s output?
I haven’t thought of it as that high frequency, I think it isn’t really, but I have not though enough to say. But it is almost perfect for a bridge. All of the decoder scematics I’ve seen start with a bridge and then regulation, for the power side.
Instead of the hassle of 4 diodes, you can just go out and buy a complete bridge rectifier already assembled as a single unit with the 4 leads, 2 in, 2 out.
Hey guys, thanks for the replies so far. I would have been here sooner but work had me too tied up. Ok, so I’m going to reply to some of the comments I’ve gotten:
Jeff (Vail and Southwestern RR),
I think I will use a bridge rectifier like the one you showed me from Wikipedia. I’m going to see if I can find an already assembled one like MisterBeasley suggested, but it will need to be small enough to fit in the location I’m planning on using it in.
I saw you reference a half bridge using two diodes, if I go this route, will it cause an on-off in the electrical flow? (even though I’m emulating an EOT) Also, what kind of diode (namely an item number) would I use to make a bridge or half bridge? Thanks.
rs2mike,
I have an EOT on a box car right now, and it’s powered by two hearing aid type batteries concealed inside the box car. What I want to do is similar to ring engineering’s idea of truck mounting the circuit and having it powered by rail, that way I can use in on spine cars, flat cars, or any other freight car that would make it difficult to hide batteries in. This is what I’m trying to shoot for: http://www.ringengineering.com/. The circuit I’m using is this one: http://www.mrollins.com/flash2.html, which is smaller in assembly than the one that Mark R. showed me: http://home.cogeco.ca/~rpaisley4/FredDCC.html. If it was a beacon light, I would have no problems using a decoder in the engine to power it, but I want to avoid wasting a decoder in a freight car just to get my FRED to work.
Texas Zepher,
The batteries I use are indeed 1.5v, and I’m using two of them, so it’s 3.0v total powering the circuit. I couldn’t find electrical data in the Bachman paper work, but the AC ada
I should have said one diode to half wave rectify it, I was napping. In theory it would be on and off, way, way, faster than your flasher. Because it is so fast, realatively, it would not really get down to zero, I think.
If you build it out of discrete part you can use about any diodes you have laying around the house![oX)] The 1N4148 in the circuits in Mark R’s post would be fine. (The first circuit in that post is using the full bridge, the second the half).
TCS makes a decoder thats called a fleet lighter. Rather inexpensive and compact. I have taken an LED with a 1K 1/4 watt resistor and put it across the rails and it lit just fine. The frequency of the DCC is so fast you cant see the off part of the light. With a FL decoder you can control and address the car so its not flashing in your yards and sidings.
Taking a digital multi meter to the rails will give you a false reading. The square wave DCC signal will be confusing to a digital meter. An older analog meter will give a more accurate reading. or you can tap into and measure the headlight output of a decoder. Track voltage is usualy the same.