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Tricky Dicky

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Everything posted by Tricky Dicky

  1. I do not know why people insist on trying to run LEDs without resistors, after all they are not the most expensive component neither do you need a vast collection of them. DC voltages associated with model railways tend to be 12V in the main. Other power sources often used such as ex-phone chargers are mostly 5V since all phone manufacturers and tablet makers have standardised on USB charging. Even the forward voltages of LEDs range from just below 2V to around 3.5V and since most modellers choose not to run their LEDs at full power the variety of resistors required is limited as long as the r
  2. No that would not work. All resistors dissipate heat the higher the current the more heat. The more heat needed to be dissipated physically the larger the surface area of the resistor needs to be. It is a fine balance not allowing a resistor to get too hot since that begins to alter the value of the resistor. This is the reason why it is recommended to provide each LED in a circuit with its own resistor thus each individual resistor has minimal heat to dissipate. Going of your figures for your coach lighting of 12.5V supply and 0.33A current draw you would require a resistor value
  3. Due to the DCC voltage being a hybrid AC most multimeters will not read the voltage correctly even on the AC setting, so your voltage numbers are highly likely suspect. Since you need a DC voltage for the LEDs anyway, connect a bridge rectifier to the coach pick ups, then measure the voltage on the output of the rectifier on the meters DC setting. Now a little maths, divide the voltage you have measured by the respective current readings you have for each set of coach lights that will be the value of the resistor you need to put in series with the LEDs. You will probably not get the exact valu
  4. Testing as you go along is advisable, if you get something wrong it usually only means one step backwards to resolve it. Having to check out a whole layout to find where a problem has manifested can be a real PITA. Richard
  5. A simple PIC could be used to monitor the number of changes of state on one input and produce the appropriate outputs even flashing lights. Richard
  6. I will concede that, but had already kind off hinted at that with the guitar string remark. The point I was making was prior to the availability of Wagos, ScotchLok was the only viable non-soldering screwless way of connecting/splicing wires that did not require a specialist tool. It is my opinion that wiring into a loom is probably better done with a ScotchLok but if wanting to take a solderless approach to wiring then I think Wago is superior in that they take a wide range of wire sizes unlike ScotchLok where you have to consider which connector to use in relation to the wires be
  7. Please explain how? You can make exactly the same kind of connection with the appropriate Wago as you can with a ScotchLok with the advantage that a Wago can cope with a greater range of wire sizes. The only circumstance I can see a ScotchLok would be better was if your wiring was strung out like guitar strings. Richard
  8. +1 for Wago connectors, they are far superior to Scotch Lok which are often recommended for quick screwless connections. Wagos will happily connect a wide range of wire from 4mm sq. down to 7/0.2. I can attest to the latter having tested to destruction, I pulled the wire apart before the Wago let go. Do go for the the genuine ones as there are a lot of clones on the market and their properties could be suspect. Richard
  9. I currently use a cheap Maplins 40W iron with supposed temperature control but I could not tell you what the temperature is set at since it is a knob control with a coloured scale going from green -cool, to red-very hot and I find setting it at 3/4 turn is right for me but i think if you can set temperature about 365C is about right. When you say the tips are burning out at high temps are you referring to the tip or the element? I suppose prolonged use at high temp will tend to take it out on an element over time but tips tend to get damaged more by abrasions. Most modern irons hav
  10. The spur should be completely isolated from the rest of the layout ie. both rails and needs its own feed. That feed should go to the centre terminals of a DPDT switch. The main feed should go to the two terminals on one side of the centre terminals and the programming feed to the other two. Just make sure the main feed is connected to the same rails as the rest of the layout otherwise you will cause a short. Richard
  11. Keith has outlined several possibilities, but at the end of the day it is all guess work and you really need to get an accurate reading of the current draw. If as you say you are having trouble finding a point where you can connect your meter in series, why not insert a thin piece of insulating material - plasticard say between one battery terminal and the contact in the battery holder then simply put one probe on the battery terminal and the other on the contact to complete the circuit. Richard
  12. Mike you have made the classic presumption that LEDs are like bulbs in that altering the voltage affects their brightness. LEDs are current driven devices and the series resistor that you get in LED circuits is a current limiting resistor. Hence as Keith has pointed out you need to establish the current draw of the LED circuit and as he has pointed out your meter needs to be in series with the battery and LED(s). As we are looking at 2 AA batteries which should be giving you 3V or 2.8V if they are rechargeable (2.4V seems odd unless the batteries are well used). The LEDs are probab
  13. Are you sure you have all the droppers connected correctly as you have indicated on the diagram. I would be tempted to as a quick fix to swap the two droppers on that siding and see what happens. Richard
  14. Take care with the red ScotchLok on 7/0.2 it wire is only about 0.3mm2 so a little under spec. The problem with ScotchLok connectors is when you have quite different wire diameters they can almost cut through large wires beyond spec. But worse on thin wires outside the specs they may not completely displace the insulation. I would advise going up to 16/0.2. Although Wagos are more geared for mains wiring the lever type will definitely grip 7/0.2. They are the ones that I have used on house wiring but have tried them on 7/0.2 and they are a good connection that will not pull out.
  15. The distributors website says they are good for up to 48V but the 1K current limiting resistor for the indicator LED suggests it is set up for 12V. Richard
  16. I would hazard a guess that the resistors you have are 0.125W. For example a standard LED with Vf = 2V and If = 10mA with a 12V supply would require a 1K resistor and the power dissipation would be 100mW(0.100W) so you can see you are very near the ability of the resistor to cope. If you are using white LEDs where the current draw can be as much as 30mA you will make the resistors run hot. I would uprate your resistors to 0.250W or even 0.5W to play safe after all you are wiring them inline with the lamps and it is not as if you are worrying about component space on a PCB. Richar
  17. Andy what is the status of images uploaded to RMWeb by copyright holders? I am thinking of the likes of Brian Lambert who has often uploaded images from his website which also appear in his book. In the past other respondents to the same thread have often reused these images even altered them as part of the ongoing discussion is this still OK? Richard
  18. I am mainly using an iPad Air to access the forum and I am finding I have to tap links twice before the link will open. This is not a problem with other websites I visit just unique with RMWeb. Richard
  19. Does the subscriber discount apply to digital subscribers? Richard
  20. Have you considered PICAXE. Not usually the first choice of PIC due to speed and memory capacity but for what you are planning will easily cope. Plenty of interfacing circuits in the free manuals and cheap to get started. http://www.picaxe.com/ Richard
  21. I would hazard a guess that it is a logic gate astable using something like a 4011 quad NAND gate IC which is a 14 pin IC. Such an astable just requires two of the four gates with inputs linked to become inverters hence why the there are no connections on one side except for the +V pin. If it is a 4011 IC it will be good for up to 15V. The 10K trimmer and the larger capacitor I would suggest are an RC circuit controlling the pulse rate. I cannot figure out what all the other resistors and capacitors are for although one might be across the voltage rails. As someone has pointed out there is a t
  22. Came across those earlier and they look good but it is a US site and they are an eye watering price of $8 each. I can see restorers of antique radio equipment being interested but for a layout? Richard
  23. You want to look in the 4mm sockets section of your suppliers catalogue where you will find variations of these which are basically a 4mm socket but combine a binding post https://www.rapidonline.com/truconnect-4mm-binding-post-with-m4-thread-red-17-0065 but if you after a traditional brass binding post then you will probably be out of luck and the nearest to it will be something like this https://www.rapidonline.com/truconnect-uninsulated-earth-terminal-17-0795 Richard
  24. I have stuck loads of cable trunking with double sided tape and generally it stays put the only times they have detached is when stuck to a friable surface. Unsealed wood is a problem particularly MDF, you just need to seal it with paint or varnish and most tapes will hold. The best type to use is the type with a foam core and the most reliable tapes are the ones used in the double glazing industry for fixing trims my local double glazing materials supplier does a range of widths and thicknesses and cheap too. Richard
  25. It's a while since I dealt with an LS150 but I do recall it does not have a built in CDU as some points decoders do, so assuming you are using solenoid motors it is probably down to a lack of current to shift several points at once. I believe if you have several LS150s the solution is to spread route setting across several decoders. Sorry it is not a very helpful answer. Richard
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