RobertW Posted December 22, 2012 Share Posted December 22, 2012 Hi Could someone please check this wiring diagram. I have drawn it in AutoCAD Electrical. I am fairly certain that it is right but it could do with a fresh pair of eyes over it. Just so that everyone s clear. the colours of the lines is the colour coding I am planning on using. The wiring sizes and numbering is indicated. Although I am unsure of the diagram's viability don't be afraid to use the technical terms as I am an electrical engineering student summer project wiring diagram.pdf Thanks Rob Link to post Share on other sites More sharing options...
Grovenor Posted December 22, 2012 Share Posted December 22, 2012 General, When copying text labels you need to edit the text afterwards to suit its new purpose, lots of copied labels that have not been edited. Track feeds, If using single pole switches then you may as well use common return wiring and save a lot of individual return wire back to the panel. Point motor feeds, Looks Ok but I have no idea what you are trying to achieve with all the lights and why the point switch is linked into them? Regards Keith Link to post Share on other sites More sharing options...
MichaelW Posted December 22, 2012 Share Posted December 22, 2012 Hi Rob, I'm afraid that without a bit more information, it's hard to tell what the diagram is being wired to. Do you have a track diagram with the connections marked? The top looks a fairly standard wiring for a DC control panel. The middle bit is unusual for a CDU - unless I'm misunderstanding something, using a toggle switch will leave one side (or other) of the point motor permanently connected, so the CDU won't be able to recharge. The bottom bit I'm really not sure about - it looks like you'll have 4 yellow lights on permanently, and either the top or bottom set of green and red - again a bit more info would help. Link to post Share on other sites More sharing options...
Gordon H Posted December 22, 2012 Share Posted December 22, 2012 Looks like the point switch symbol used is for is a DPDT biased to centre-off. With this arrangement, one pole is being used to change the point (with or without CDU) and the second pole sets or resets the 555 which is configured as a bistable latch. Thus when the point switch is operated one way, a coil fires and the LEDs adopt one state. When the point switch is operated the other way the other coil fires and the LEDs adopt the opposite state. Otherwise the switch is in its centre-off position and the LEDs stay put. That appears to be the intention, but quite why there are so many LEDs operating from it with apparently alternating colours remains a mystery. Link to post Share on other sites More sharing options...
naugytrax Posted December 22, 2012 Share Posted December 22, 2012 The bottom bit I'm really not sure about - it looks like you'll have 4 yellow lights on permanently I think the clue to this is C1 - labeled "yard lighting fadeout". These 4 LED's are fed by their own switch off the 9V supply. They are intended to stay on until switched off, at which time C1 will discharge and let the lights down gently. The current in the legend seems too high - surely it should be 20 mA rather than 120 mA? Assuming the yellow LEDs operate at 2 volts, four of them in series requires 8 volts. So the 56 ohm resistor drops 1 volt (from 9 to eight) at a current of a lttle less than 20 mA. I've always stayed away from connecting LEDs in series, since if one of them fails the whole string goes out and then you have to take each one out of circuit in turn to find out which one blew - just like the d*** lights on the Christmas tree! I prefer to wire them in parallel with a dedicated resistor for each - the cost of 3 more resistors is not significant. [edited to add missing right parenthesis] Link to post Share on other sites More sharing options...
RobertW Posted December 22, 2012 Author Share Posted December 22, 2012 Gordon H The DPDT centre off switch changes both the point motor and the state of the 555 timer by taking either the trigger or reset low. this changes the signals for the point. As the layout is based on BR served industry in North Lincolnshire the signals aren't to BR standard. There are four signals so four LEDS per state. naugytrax There are four LEDs in series. these have an individual current of 30mA and a voltage of 2.5V. This current is multiplied by the number of LEDs in the leg of the circuit. This is 120mA. this is put into the resistor formula (i.e. Rl = (Vs - Vl)/Il to get the resistance. Therefore (9-2.5)/0.12 = 54.16. Next highest resistor is 56R. Hope this makes it clearer Rob Link to post Share on other sites More sharing options...
naugytrax Posted December 23, 2012 Share Posted December 23, 2012 Hi, Rob: your calculation for the 4 yellow LEDs applies if they are connected in parallel. But your diagram shows them connected in series. In the series case, the same current flows through all of them. And BTW 30mA will almost certainly give too much brightness. Also if the LEDs' conduction voltage is 2.5, you can't run 4 of them in series from a 9 volt supply! So I think your diagram needs revision in this area. Link to post Share on other sites More sharing options...
RobertW Posted December 24, 2012 Author Share Posted December 24, 2012 Seeing as I have two spare connections on the lighting board, would it work to connect two of the LEDs in parallel to the other ones. i.e 30mA in one leg @ 5V and 30mA in the other leg @ 5V. Spec for LEDs here (http://www.maplin.co.uk/5mm-leds-2047) Rob Link to post Share on other sites More sharing options...
cpman46 Posted December 24, 2012 Share Posted December 24, 2012 Rob The Maplin spec says 30mA MAX. It is not good practice to run LEDs or any other item for that matter at its maximum. Since each LED drops 2.5V you cannot run 4 in series but you could run 2 pairs in series each with its own current limiting resistor from your 9V supply to replace your existing single 4 in series circuit. This leaves your spare circuits available for other things if required. I would suggest you run the LEDs at no more than 20mA by using a 220R resistor for each series pair. As has been pointed out in a previous post (naugytrax) you may find that they are still too bright running at 20mA so will need to up the resistor value to reduce the current and hence the brightness. (A 270R resistor would give you roughly 15mA through the series pair, 390R approximately 10mA). Standard 0.25W resistors will be more than adequate for the power dissipated. Hope this helps Link to post Share on other sites More sharing options...
RobertW Posted December 24, 2012 Author Share Posted December 24, 2012 I have changed the wiring digram as per your suggestion. Would it be possible for me to wire the lighting units with 7/0.2 wire or would this still create too much voltage drop. then I don't have to force 4 lengths of 16/0.2 wire up a 4mm tube. Thanks for all your help. Rob summer project wiring diagram Full Wiring Diagram.pdf Link to post Share on other sites More sharing options...
Grovenor Posted December 24, 2012 Share Posted December 24, 2012 You want volt drop, that's why you are putting resistors in. For wiring signals 7/0.2 is still to big, best you find something smaller. A 4mm tube is also to big unless you are modelling in 7mm scale, signal masts are just under 6 inches. Keith Link to post Share on other sites More sharing options...
RobertW Posted December 24, 2012 Author Share Posted December 24, 2012 If I use 7/0.2 wire the voltage may drop below Vl as the battery runs down. this would turn the lights off completely. The next smallest size is 1/0.2 (i.e. single core) this will create extra, unwanted voltage drop. It is also a lot weaker and is liable to snap if it is moved around. as this is a portable layout it would be best to use stronger wire. Thanks for your help Rob Link to post Share on other sites More sharing options...
cpman46 Posted December 24, 2012 Share Posted December 24, 2012 Why a battery? Do you have a 12V dc source available? What is feeding your CDU? Can you derive a 12V dc supply from the feed to the CDU? For wiring your lights 10/0.1 wire is quite thin and unless you are running miles of wire voltage drop will not be a problem. Don't understand the quote 'liable to snap if moved around'. Think we need a bit more detail regarding the lights e.g. fixed to layout, removeable etc. Link to post Share on other sites More sharing options...
RobertW Posted December 24, 2012 Author Share Posted December 24, 2012 The CDU is fed from a 15V 250mA transformer (http://www.maplin.co.uk/miniature-250ma-transformers-3688). It is a separate module and and plugs into a dedicated socket on the side of the layout. Single core wire is designed for joints that are made and then not hauled around because there is only one conductor and this make it weaker. If the joints are moved i.e. during cabling up then the joints can snap. I am trying to keep the CDU auxiliary electrics and the 9V DC electrics separate. The lights weren't intended to be removable. The LEDs need all the current they can get as they aren't very bright (5 milliCandela). Rob Link to post Share on other sites More sharing options...
cpman46 Posted December 24, 2012 Share Posted December 24, 2012 How about a plug top 12V dc supply, plenty available on eBay or Rapid Online do a 12V 500mA one (Code: 85-3071) for instance. Your transformer is naked so I assume you will be building it into a suitable enclosure with the appropriate fusing and earthing. Brighter LEDs are available e.g. Rapid 55-0125 Yellow 20mcd @10mA. Can't quite understand the comment of hauling cables around and cabling up. Are we talking about cross board cabling or fixed wiring on each baseboard? Link to post Share on other sites More sharing options...
RobertW Posted December 24, 2012 Author Share Posted December 24, 2012 The layout is a single board. However as the runs of cable are put into the main run and cable clipped down then it pulls the cables around and single core wire will snap. It is theoretically possible, But, because the PP3 (9V battery) is linked using a snap to change this to a 8 x AA battery box as this develops 12V. I may use the Rapid 1A (as this is a maximum it will draw). However I will need to change the LED resistors in the signal module (from 330R to 470R). I have a 12V 5A transformer in the controller (Isolated Winding i.e. 0-12 0-12) and it may be possible to use the second winding from this to power the signals & lighting. As I am using Phono plugs to link everything together I can just add another set. Could I use the 12V Auxiliary Winding to Power The CDU as well. If I was to build a separate power pack for the layout, i.e. The 12-0 12-0 transformer and the 15-0-15 Transformer, would that work better. Also, as the 12V transformer has a rating of 5A, is that 5A per winding or 5A for both of them. Rob Link to post Share on other sites More sharing options...
Grovenor Posted December 24, 2012 Share Posted December 24, 2012 The layout is a single board. However as the runs of cable are put into the main run and cable clipped down then it pulls the cables around and single core wire will snap. I would not recommend single core wire for signal masts, but as others have said there are smaller wires than 7/0.2 available such as the suggested 10/0.1 The wires coming down the signal mast should be terminated in a terminal block, or better a plug and socket close to the signal and a larger wire used for te main run for the reasons you suggest. Single core wire, eg 0.5 mm2 telephone cable is best for droppers connected to the rails as it is much easier to solder neatly and unobtrusively to the rail, again just in short lengths to terminal blocks/strips under the board. Regards Keith Link to post Share on other sites More sharing options...
cpman46 Posted December 24, 2012 Share Posted December 24, 2012 I assume from your last posting the transformer is contained within the controller and the 12V outputs are available on terminals. If the 12V transformer is marked 60VA then each winding will be 2.5A. If you use the second winding to power your LEDs you will need to fit a bridge rectifier of suitable rating to rectify the ac volts. This will give you unsmoothed dc of approx the same voltage. However, you are using it to power the 555 timer which will need a smoother supply so a small electrolytic capacitor say 100uF at 25V will be required on the output of the bridge which will increase the output voltage seen to about 16V. This is close to the max operating voltage of the 555 and personally I would prefer to limit the voltage to something lower say 12V using a voltage regulator which will add extra complexity to the circuit. you could use the same winding to power your CDU taking a connection before the bridge rectifier (this would negate the need for the 15V transformer). What/whose CDU are you proposing to use? Whose point motors? If you have not already done so I would recommend looking at Brian Lambert's web site http://www.brian-lambert.co.uk Regards Link to post Share on other sites More sharing options...
RobertW Posted January 7, 2013 Author Share Posted January 7, 2013 I have taken all your advice on board and have changed the diagram. I have designed a new powers supply. just so you know T3 is a TIP31 in the controller and the power amplifier in the CDU is a BDX33C. These are both Heatsinked so they require earthing. is it a good idea to use 3 core mains cable for this task. I am planning on using a http://www.maplin.co.uk/general-purpose-abs-plastic-box-a-e-series-43708 E series boc to house the controller and another one to house the power supply. The project has gained a name, as there are three projects on the layout being done. Rob Project Volta Full Wiring Diagram.pdf Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted January 7, 2013 RMweb Premium Share Posted January 7, 2013 I have taken all your advice on board and have changed the diagram. I have designed a new powers supply. just so you know T3 is a TIP31 in the controller and the power amplifier in the CDU is a BDX33C. These are both Heatsinked so they require earthing. is it a good idea to use 3 core mains cable for this task. I am planning on using a http://www.maplin.co.uk/general-purpose-abs-plastic-box-a-e-series-43708 E series boc to house the controller and another one to house the power supply. The project has gained a name, as there are three projects on the layout being done. Rob Like cpman46, I wonder why you feed your CDU with 15 Volts DC. You'd be much better off removing the bridge rectifier & use the rectifying properties within the CDU (depending if it is a typical one). Link to post Share on other sites More sharing options...
RobertW Posted January 7, 2013 Author Share Posted January 7, 2013 The CDU is made from this circuit diagram (http://talkingelectronics.com/projects/CDU-2/CDU-2.html) the BD679 is replaced by the BDX33C It is also easier to use 15vDC as then it isn't putting more strain on the 2 amp limit placed on the auxillary power supply, allowing to work well within it's safety margin. As the CDU only half rectifies the voltage i thought that it would be best to Full Wave and regulate the voltage before it left the power supply. Link to post Share on other sites More sharing options...
Grovenor Posted January 7, 2013 Share Posted January 7, 2013 As the CDU only half rectifies the voltage i thought that it would be best to Full Wave and regulate the voltage before it left the power supply The bridge rectifier does no harm but the CDU will charge to the peak voltage of the waveform, whether it is half wave of full wave is largely irrelevant, it will, however, charge up a bit quicker on full wave if that matters to you. The 15V regulator is another matter, that should be removed. To get best performance from solenoid point motors the CDU should be charged to around 22V. This will be what you get with the unregulated transformer output but your 15V regulator will limit the CDU voltage to 15V max and spoil its performance. Regards Keith Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted January 7, 2013 RMweb Premium Share Posted January 7, 2013 The CDU is made from this circuit diagram (http://talkingelectronics.com/projects/CDU-2/CDU-2.html) the BD679 is replaced by the BDX33C It is also easier to use 15vDC as then it isn't putting more strain on the 2 amp limit placed on the auxillary power supply, allowing to work well within it's safety margin. As the CDU only half rectifies the voltage i thought that it would be best to Full Wave and regulate the voltage before it left the power supply. Nothing wrong with that circuit and indeed Talking Electronics is an excellent source of all manor of kits to suit modellers. The only thing I would question is why any reference to using 15V DC as a power source? The description is totally based on using AC as a source, other than showing what the polarity MUST be if using DC. It certainly doesn't state that it will work identically, as it cannot. The circuit will charge fairly quickly (it states 'less than 1/2 a second') so your reference to 'straining the 2 amp limit' makes little sense. Link to post Share on other sites More sharing options...
RobertW Posted January 8, 2013 Author Share Posted January 8, 2013 The problem with using the CDU as is that the AC source, half rectified can cause the solenoids to buzz as they are used. surely it would be better to eliminate the hum that is caused by the AC source. In my mind I would prefer to separate the High current point control systems from the low current systems for the signals and lights. On a completely different note what would be agood connector to connect the 2 sources to the layout. I don't need to worry about the controlled 12V output as that already has a cable. On another note, should the on-board electrics, i.e. the bits in the dashed boxes work, because i have the wire to rewire the layout so am itching to get started. Thanks for the help Rob Link to post Share on other sites More sharing options...
naugytrax Posted January 8, 2013 Share Posted January 8, 2013 the AC source, half rectified can cause the solenoids to buzz as they are used. No need to worry about this. The length of the pulse from the CDU, and the motion of the turnout blades, is so short that it would not be possible to hear any buzzing from the solenoids, even supposing that the CDU output somehow contained some AC ripple despite the whacking great capacitor across the output! The only thing you should ever hear from the solenoids is a brief click, regardless of whether the CDU is fed with AC or DC. If the solenoids are buzzing, the CDU is wired incorrectly AND the wrong kind of switch (not a momentary-contact type) has been used as a turnout control. Link to post Share on other sites More sharing options...
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