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Crosland

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    www.sprog-dcc.co.uk

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    Warwickshire, UK
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    DCC 2mm

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  1. I have thought of a DCC-DMX accessory decoder for controlling layout lighting rigs but I think DMX is closed source and I was too tight to buy the spec There's also DALI which has hardware support in some PICs. I would like to see those waveforms zoomed in a bit, and/or sampled at a faster rate, hence my earlier comment.
  2. That photo prompts a question: How long has the double square symbol been in use?
  3. If you want to retain your sanity, don't look at a DCC waveform with a 4GHz scope
  4. Shortening the pins won't make it fit in any better but beware some sockets can allow long pins to stick out the other side and short out on metalwork. So shortening can prevent shorting
  5. The 2mm Scale Association Track book shows how to make some very simple filing jigs that could be adapted to other scales.
  6. I remember in the days of 405 line TV our picture turning to snow when a neighbour 6 doors down (honestly) revved his car. You will find very few cases these days. A lot of cases of interference, especially TV, are due to poor receiving equipment, e.g., years old, corroded, aerials and downleads. Wires just poked in the back of the aerial socket, etc. The move to digital caused a lot of such stuff to be upgraded, e.g., where the digital signals were in a different channel group, so TVs are a lot less receptive to interference. In the digital world, fitting a decoder means that the wires from the motor are much shorter and not directly attached to the track, so the facility for commutation noise to be broadcast via a layout sized aerial is much reduced. <pedant mode> Suppression components are not actually a legal requirement. The legal requirement (when sold) is that the equipment (i.e., the loco) does not radiate excessively. What you do to it in your own home is up to you, so long as you do not spoil other peoples enjoyment of the Archers </pedant mode>
  7. The "proper" way to use screw terminals is to crimp a bootlace ferrule on the end of the wire. It will not flow under pressure from the screw like solder can, coming loose over time. In your case it will probably just exacerbate the problem with the small connectors. There's no harm in using a very short run of thinner wire from the connector to the thicker wires. Any voltage drop will be minimal over an inch or two.
  8. This ^^^ They do no harm, unless you decide to go digital.
  9. That's TWO rabbit holes opened
  10. To help in describing conditions we could do worse than take a leaf out of the domestic wiring book. "high impedance short" is an oxymoron. A too high current that does not cause a trip, is an overload. It's beyond the design parameters of the equipment but does not necessarily cause an immediate, catastrophic, failure. You can, for example, overload the fuse in a 13A plug for a long time, depending on the magnitude of the overload. A true short circuit is a "fault" that needs to be detected quickly, e.g. by blowing a fuse or tripping a breaker. DCC boosters have (should have) fast acting overload protection but there will always be a grey area between the stated limit and the actual trip current, due to component tolerances. Allowance for this should be built into the booster.
  11. Thermal transfer pad to connect the components to the heatsink.
  12. Aside from the lower voltage the Rapid one is only 6VA so 30V @ 200mA or 15V @ 400mA or 2x15V at 200mA each. Assuming the GM one is 1A on both outputs simultaneously, it is 32VA or 5x "bigger". You need to compare like-for-like Rapid have 2x15V 25VA and 50VA in the same range. How much current do you need from each winding?
  13. Sorry but what you are describing is not DCC. If you want to know how DCC works then I suggest you read the NMRA standards. They are freely available on the NMRA website. I'm tiring of correcting the nonsense that gets written about DCC. Depends how you measure it. If you measured between ONE rail and the booster 0V connection then you would see a square wave switching between 0V and the positive track voltage. Measure the other rail in the same way and it will be 180 degrees out of phase. On the layout all you have is the two rails. Half the time one rail is more "positive" than the other. The other half of the time it's more "negative". There are no absolute "positive" or "negative" voltages, just the voltage difference between the two rails.
  14. Thinking aloud: I would put two LEDs in series with a current limit R for 12V and use a 12V zener. Lets say the LEDs want 10mA for desired brightness so 50mA in total for 5 pairs. Say 20mA through the zener so 70mA in total. With 14V input you need another R of (14-12)/.07 or 28 ohms. At 19V input the current through this R will increase to 7/28 or 250mA. All of the excess current will be dumped through the zener and the power dissipation will be 1.75W worst case, so you will need a fairly beefy zener. At room temp. with the low currents involved, a 7812 regulator should work with a 14V input.
  15. I'm not sure what your statement means. The track power is DCC. You can't say one is AC and one is DC! Now consider what you measure between the two rails of a DCC layout. The current flows one way, then it flows the other way. The current alternates. Do you see where I am going with this? The only time a DCC signal is DC is if you measure ONE track output with respect to the 0V supply to the booster. Even then, being pedantic, it has a DC component and an AC component. On the layout there is no fixed reference, only the two rails. What you see is AC. The NMRA use the term "bipolar", but not "bipolar DC" as far as I can see, to describe DCC in the standards. I suspect it's an American thing where they seem to assume AC is always low frequency that you get from the mains.
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