Crosland
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Everything posted by Crosland
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Alan Gibson OO back to back gauge new price £5.90. I just sold mine for nearly £12 plus postage. Defies all logic, but I'm happy :-) Andrew
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I've only just notice that the "you won" e-mail to the buyer that is copied to the seler includes the buyers maximum bid. Is this a new feature? Andrew
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If you plug an 8-pin decoder in the wrong way round then nothing bad will happen, but the motor drive will still work. The track pickup and motor connections aredeliberately placed on the diagonal corners so that a reversed decoder will still be connected to the track and motor (although both connections will be reversed). The lights will not function as expected. Andrew
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No need to "convert" anything, nor open the box. The command station can be used as a booster by connecting the DCC signal from your command station to the 4-way "booster out" connector. From memory I think it's the outer pair of wires. Beware that Roco boosters have no overload protection when used this way. Andrew
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Hattons DCC Decoders
Crosland replied to Free At Last's topic in DCC Discussion Topics (not questions)
BEMF control of a motor involves a PI or PID control loop with feedback from the motor. It can only be 100% truly effective if tuned for every individual motor (or at least motor type). This is quite a technical process and would be beyond most modellers. Anything else is just a varying degree of compromise. The better decoder manufacturers give you CVs to allow you to tune the control loop. Lenz just have "motor type" with little explanation. I don't know exactly what CV10 does on the DCC concepts decoders. At the other end of the scale you should be able to adjust the P, I and D constants. The Zimo decoder manuals give an idea how much adjustment there can be. At high speed the time taken to perform the BEMF sampling can adversely affect control and there should be a CV to set the speed at which BEMF is reduced or turned off altogether, so "partially disabling" BEMF may be exactly the right thing to do, depending what CV10 is actually doing. Zimo decoders adjust the BEMF sampling automatically. I don't think any of the issues described are down to faulty decoders, just that they need to be setup for the loco they are used in. Andrew -
Inductors (chokes) for suppression. They pass DC but block AC (so the opposite to suppression capacitors) and are wired in line with the feeds from the track. They would block the DCC signal, hence they are on the blanking plug to be removed when you fit a decoder. If they were not on the blanking plate then you would need to replace them with wire links Andrew
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It would help to know whose reference numbers they are, but a simplistic reading would suggest they wil be OK. I am hoping the 3500W is a "foreign" way of saying 3500V and relates to the insulation break down voltage. If the 3500W is a power rating then that would ring alarm bells for me. I would not buy cable from anyone quoting such, as it shows a staggering level of ignorance about how cable is specified. Andrew
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For those who are interested, the data sheet parameter is "reverse recovery time", Tr or Trr. You want something in the 10s of nanosecond range, definitely sub-100ns. Andrew
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I'm experimenting with this one on my layout http://xkcd.com/730/ Andrew
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Which way round for Bachmann 6 pin n gauge decoder
Crosland replied to TomJ's topic in DCC Help & Questions
Having designed decoders and looked at other designs I can assure you that either motor output can safely be connected to the blue wire through a bulb or LED with ballast resistor. The current will be well withinn the capability of the motor output. If you are so sure, please explain how the damage occurs. When both functions outputs are off, both sides of the motor are floating and no current flows. If either is on, the other is still floating and no current flows. If both are on then both sides of the motor are at the same potential and no current flows. Andrew -
Which way round for Bachmann 6 pin n gauge decoder
Crosland replied to TomJ's topic in DCC Help & Questions
Unles the loco wiring is faulty (which could cause damage either way) It is fail safe the way it is. Normally you would have: Decoder -> Socket Motor Right -> motor A Motor Left -> motor B Rail Right -> rail A Rail Left -> rail B Headlight Front -> front lights Headlight Rear -> rear lights With the decoder reversed: Decoder -> Socket Motor Right -> rear lights Motor Left -> front lights Rail Right -> rail B Rail Left -> rail A Headlight Front -> motor B Headlight Rear -> motor A The DCC reversal from the rails is immaterial unless you are using Asymmetric DCC. If a motor output switches low it will pull current through the lights from the blue wire. The resistance of the bulb, or LED ballast resistor, will limit the current to a safe level. The function outputs are open collector (designed to be connected to the +ve blue wire through a load) so there is no current path through the motor whatever they do. Andrew -
You may find it's the bulb putting out infra-red light that is interfering with the Dynamis, rather than mains borne interference. Andrew
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ZTC 611 UPDATED CONTROLLER!
Crosland replied to traction's topic in DCC Discussion Topics (not questions)
And, indeed, well before ZTC. Andrew -
ZTC 611 UPDATED CONTROLLER!
Crosland replied to traction's topic in DCC Discussion Topics (not questions)
Exactly, hence my earlier comment "It wil have it's own completely unique set of new bugsfeatures :-)" which some people didn't seem to understand. From my own dealings with the old ZTC, even they didn't understand all of their own products. Andrew -
DCC reversing loop - how easy, how costly
Crosland replied to Harry2013's topic in DCC Help & Questions
That's not realy an issue. The train has to be shorter than the reversing loop, otherwise it will collide with itself. Andrew -
Perspex is a trade name. I have always though it is acrylic. Anyone know for certain? Andrew
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There is a price list with ordering details buried on the blog, but it is certainly not easy to find. Andrew
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ZTC 611 UPDATED CONTROLLER!
Crosland replied to traction's topic in DCC Discussion Topics (not questions)
BTDTGTTS. It wil have it's own completely unique set of new bugsfeatures :-) Andrew -
ZTC 611 UPDATED CONTROLLER!
Crosland replied to traction's topic in DCC Discussion Topics (not questions)
It depends how the command station implements direct bit mode. Digitrax decoders are (or at least used to be) particular about the exact sequence of operations (the spec allows for some variation) where other decoders are not. Andrew -
ZTC 611 UPDATED CONTROLLER!
Crosland replied to traction's topic in DCC Discussion Topics (not questions)
That's more suggestive of different modes being used, e.g. it's using page mode for the Lenz and direct bit mode for the Digitrax. Easy way to tell is if the time to read a CV varies with the value. Page mode tries up to 256 values until the decoder replies "correct". Direct mode can always do it in 8 or 16 operations. Andrew -
ZTC 611 UPDATED CONTROLLER!
Crosland replied to traction's topic in DCC Discussion Topics (not questions)
Yes, I heard the same. There is some blurb on their homepage that states he was a sub-contractor to ZTC as well as a user. Andrew -
ZTC 611 UPDATED CONTROLLER!
Crosland replied to traction's topic in DCC Discussion Topics (not questions)
Other way round. Andrew -
The day after the 2mm chassis workshop in Oxford. Ready to jump in at the deep end for my very first 2mm build: It's not quite so tidy now! Testing the chassis Tender chassis And body Unfortunately progress has been stalled for quite a while. I hope to get going again over the Christmaas break. Andrew
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Substitute the reactance for resistance and you are still using Ohm's law to all intents and purposes. A true RMS meter will work with any arbitrary waveform, that's what they are designed for. It doesn't matter if the circuit is resistive or reactive, you are measuring the voltage at the terminals of the circuit, or the current flowing into it. You may be getting confused with power measurement where you need to take the power factor into account for non-resistive loads. Andrew Crosland
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I suggest you stop digging right there. Pass an AC current through a resistor and Ohm's law applies just as it does anywhere else. RMS calculations are accurate and work for any shape waveform and frequency. Measuring AC with a cheap hobbyists multimeter is OK for 50 or 60Hz sinewaves, which these meters are designed for, i.e. signals derived from the household mains. I suggest you read http://cp.literature.agilent.com/litweb/pdf/5988-6916EN.pdf and then explain where you think the approximation comes into an RMS calculation, and why it only works for sine waves. It's simply a series of mathematical operations and the accuracy is limited only by the precision of your calculator. Buy a "true RMS" meter and you can measure any waveform and frequency with an accuracy subject to the limitations of that particular meter. Andrew Crosland