wiggoforgold Posted February 22, 2014 Share Posted February 22, 2014 I'm designing a new power supply unit. It needs to contain 3 Gaugemster transformers which supply the controllers, points etc, and an old Hornby transformer which supplies the uncouplers. I would like to wire the transformers to a single mains socked which wpuld then be plugged in. How do I do tjis safely? As a supplemental, searching this forum revealed a comment that cases for power supplies should be fireproof, metal. Obviously they should be fireproof, but I hadn't come across a requirement for metal cases before. A friend who was a firefighter and frequent exhibitor used to use wood, and when I discussed the design of these case with him, he was happy to use wood. His only comment was that the finished article should be raised off the floor so it didn't have the potential to leave a mains supply on the floor in a pool of water. Alex Link to post Share on other sites More sharing options...
woodyfox Posted February 22, 2014 Share Posted February 22, 2014 Go to an aquatic supplier and search for a 'cable tidy'. They are used on aquaria to supply all the electrical equipment safely from a single plug. I would say you'd pay ten pounds for one with one mains input leading to four outputs (2 switched) with a power on lamp. They are perfectly safe. One outlet would normally control upto 400w heater, 40 to 60w lighting and 20 w worth of pumps etc... Link to post Share on other sites More sharing options...
Gruffalo Posted February 22, 2014 Share Posted February 22, 2014 Most transformers are now supplied as "double insulated" and will have a symbol on them that looks like a black square with another black square inside it if it doesn't need to be enclosed. Such transformers only have a brown and a blue wire - no earth connection. Each device should be protected by a (maximum) 3 amp fuse. Each Gaugemaster would not normally draw 1 amp on the primary circuit so a 3 amp fuse in your plug should also be ok. If you are dismantling Gaugemaster units to rebuild them into a new panel you need to avoid creating a potential for mains to get to the outside case. Your fireman friend has surrounded his transformer with an insulator to avoid power reaching the outside but you also need to consider the feet. I don't know how big is your layout but that seems a lot of power to me. Allowing 1 amp for each running loco with say 3 of those and another 2 amps for accessories would give 5 amps demand from the secondary if all run at 12v dc, that is 60w total secondary. Taking that from one transformer requires that one to be rated at 100w on the primary side, less that 0.5 amp! Do you really need three Gaugemasters? The three regulators are on the secondary side - only needing a low voltage supply. If you consider your real costs, the components, the time to do this, the enclosure etc, you will find buying a controller is much cheaper AND it removes the safety risk to being done by specialists. Gaugemaster do twin-channel controllers and used to do a four channel unit. Points are controlled by solenoid units and these are best connected via a capacitor discharge unit. These don't take a lot of power. If you are using slow-action geared motors (tortoise, cobalts etc), you need to run these at 9v and not more! LED lighting is better supplied separately at lower voltages but if you want to stay at 12v, remember to include dropper resistors. If you enclose any transformer, it will generate heat that needs to be dissipated, hence the metal cases because they act like radiators. Electrics should never be on the floor. Not only could spilled water get onto them but ther issues of trailing wires create trip hazards too. Link to post Share on other sites More sharing options...
RMweb Gold unravelled Posted February 22, 2014 RMweb Gold Share Posted February 22, 2014 There used to be multi cable plugs. I bought one to do just what you want, but I don't recollect seeing them on sale for years. They looked like a slightly chunky plug, with at least 3 input cables. I guess since we've been discouraged from rewiring plugs, they've been superceeded by multiwaytrailing sockets. I'll look for it later, and try to get a name. Dave Link to post Share on other sites More sharing options...
RMweb Gold unravelled Posted February 22, 2014 RMweb Gold Share Posted February 22, 2014 Found sonething similar http://www.ebay.co.uk/itm/Multiway-Mains-Plug-For-DIY-Naim-Hydra-Cable-Lead-/260735158953 Dave Link to post Share on other sites More sharing options...
wiggoforgold Posted February 22, 2014 Author Share Posted February 22, 2014 Thanks for the replies. The layout isn't so big as to need three Gaugemasters to run the trains, One is enough for that! I don't need to buy any transformers, I'm just using what I've got. Intended transformer use in the power supply is as follows: Gaugemaster - powers 2 controllers Gaugemaster - provides power supply for point motors. The point motors are Tortoises and the 16v ac output at the transformer is run through steering diodes to SPDT switches in accordance with the manufacturer's instructions. .Gaugemaster - is a spare. I've always carried a spare Gaugemaster in my toolbox to exhibitions after club layout I was helping to operate suffered a transformer breakdown which had to be changed on site. I decided that rather than leave the spare in the tool.box, I would install it in the powers supply. The 16v outputs all go to identical DIN sockets so the individual transformers are not dedicated to a particular purpose, and the leads from the outputs could quickly be chan ged over id required. Hornby - this is an old Hornby trainset controller (I think it was from the "Percy" set my son had when he was small), which is turned down to power the solenoids for the uncouplers. I agree I remember multi cable plugs, but a recent search of well known DIY super stores hasn't revealed any. The aquatic supplier idea is useful, and I will investigate our local supplier. Thanks again for all the help. Alex Link to post Share on other sites More sharing options...
Silver Sidelines Posted February 22, 2014 Share Posted February 22, 2014 Hi Alex I guess I must be missing the point but from what you say I would be using standard plugs for each transformer and plugging them into a single 4 way extension socket Regards Ray Link to post Share on other sites More sharing options...
RMweb Premium QWILPEN Posted February 22, 2014 RMweb Premium Share Posted February 22, 2014 Found sonething similar http://www.ebay.co.uk/itm/Multiway-Mains-Plug-For-DIY-Naim-Hydra-Cable-Lead-/260735158953 Dave Personaly as a qualied electrican I would not trust this type of plug , there is no bs appoval & no EC kite mark. there are many other ways such as a 4 way extension leadthat can do the job much more safely . Steve Link to post Share on other sites More sharing options...
Judge Dread Posted February 22, 2014 Share Posted February 22, 2014 Personaly as a qualied electrican I would not trust this type of plug , there is no bs appoval & no EC kite mark. there are many other ways such as a 4 way extension leadthat can do the job much more safely . Steve I am also a retired electrician and I would agree to the use of an extension lead. Personally for my exhibition layout I use a drum type extension lead to bring power to underneath the control point. Incidentally it does not need to be fully extended as the total load is but a small fraction of it's capacity. Plugged into it I have a very short four way extension lead from which go the two feeds to the lighting fascias. For transformers I use the moulded plug in type as boxes, wooden or not are just not required. When it comes to PAT testing, that stops at those transformers as far as the track work etc is concerned. The florescent fittings in the overhead fascia do need to be earthed. All plug tops should have a suitably rated fuse fitted. Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted February 22, 2014 RMweb Gold Share Posted February 22, 2014 Mount all the transformers in a suitable enclosure, then hand it over to someone who knows what they're doing to wire it up for you. That you need to ask here would be enough warning to say don't try to do this yourself. Andi Link to post Share on other sites More sharing options...
wiggoforgold Posted February 22, 2014 Author Share Posted February 22, 2014 Ray My original aim was to reduce the number of plugs, but having thought about it some more, and considered the replies here I'm thinking the extension lead might be the way forward. Alex Link to post Share on other sites More sharing options...
RMweb Gold TheSignalEngineer Posted February 22, 2014 RMweb Gold Share Posted February 22, 2014 Ray My original aim was to reduce the number of plugs, but having thought about it some more, and considered the replies here I'm thinking the extension lead might be the way forward. Alex An added advantage being that you can unplug each item separately. With one of those Naim multiple cable jobs it's all on or all off. Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted February 23, 2014 RMweb Premium Share Posted February 23, 2014 An added advantage being that you can unplug each item separately. With one of those Naim multiple cable jobs it's all on or all off. Agreed, my club once had a transformer fail during an exhibition & since it was wired as proposed by the OP, no trains or anything ran, until the box was opened up, various wires unsoldered, tested, problem transformer identified, re hook the rest together minus one transformer, then tested. So much for the time saved, by only plugging in one mains cord! Link to post Share on other sites More sharing options...
Judge Dread Posted February 23, 2014 Share Posted February 23, 2014 Agreed, my club once had a transformer fail during an exhibition & since it was wired as proposed by the OP, no trains or anything ran, until the box was opened up, various wires unsoldered, tested, problem transformer identified, re hook the rest together minus one transformer, then tested. So much for the time saved, by only plugging in one mains cord! A few years ago I was at an exhibition when the power to the main hall failed 5 mins before opening time. The resident electrician was having what we call in Hull, "a duck fit". He could not find the fault but I offered to him an observation that the layouts on the stage where all working, to be told the obvious, "But it's the hall that isn't!". "Run a couple of extension leads from the stage then and plug in the dead layouts" was my reply. Incidentally, it was a fuse blown on one phase of a three phase supply that caused the panic and was replaced by an electrician from the local power supplier. Unequal phase balancing for the uninitiated. Link to post Share on other sites More sharing options...
RMweb Premium Andy Hayter Posted February 23, 2014 RMweb Premium Share Posted February 23, 2014 Ray My original aim was to reduce the number of plugs, but having thought about it some more, and considered the replies here I'm thinking the extension lead might be the way forward. Alex If you go this route, I strongly recommend that all of the plugs from transformers are taped to the extension sockets. Unplugging one transformer while the others are plugged in can be lethally dangerous. Let us suppose 2 transformers feed the tracks (2 separate sections, controllers or circuits). If you have a short between the 2 sections or perhaps a loco bridging the break between the two, then one section can be electrically from the other. So unplugging transformer 2, means that section 2 is still live at up to 12V from section 1 and its transformer. Although transformer 2 is not connected to the mains it is still operational, taking the 12vDC feed and converting it back to 230V - which will be available for anyone picking up the unplugged plug by the metal pins. The worst you are likely to get is a nasty shock and burn, but in the wrong circumstances it could be fatal. Link to post Share on other sites More sharing options...
Il Grifone Posted February 23, 2014 Share Posted February 23, 2014 If you go this route, I strongly recommend that all of the plugs from transformers are taped to the extension sockets. Unplugging one transformer while the others are plugged in can be lethally dangerous. Let us suppose 2 transformers feed the tracks (2 separate sections, controllers or circuits). If you have a short between the 2 sections or perhaps a loco bridging the break between the two, then one section can be electrically from the other. So unplugging transformer 2, means that section 2 is still live at up to 12V from section 1 and its transformer. Although transformer 2 is not connected to the mains it is still operational, taking the 12vDC feed and converting it back to 230V - which will be available for anyone picking up the unplugged plug by the metal pins. The worst you are likely to get is a nasty shock and burn, but in the wrong circumstances it could be fatal. This advice is sound and certainly recommended. However while this could be true if using DCC (or some obsolete AC system), but, in a DC system, feedback to the second transformer should be blocked by the rectifiers. Nevertheless it is good practice to never touch the exposed pins of loose plugs - I have had shocks from TV set plugs for example. For safety any portable equipment should be fed from a plug equipped with an RCD - portable plug-in ones are available for a few pounds. Do not rely on exhibition halls etc. being provided with them (even though they should be). http://www.screwfix.com/p/masterplug-rcd-plug/44855 (No recommendation or guarantee intended - just an example) This is a plug to replace the one on the extension lead, but an adapter is available. Link to post Share on other sites More sharing options...
Il Grifone Posted February 23, 2014 Share Posted February 23, 2014 Andy, I think you've misinterpreted the OP. He is not proposing switching all transformers in parallel on the secondary side. If he would, your reply would be perfectly valid and I'm sure any electricity guys on here would have flagged it in big banner headlines not to do such thing. Instead the OP is creating several circuits that each power a part of his setup, w/o any connection to the remainder. That's perfectly fine of course As I understood it, he was talking about an accidental contact, which is always a possibility, however careful one is.. Link to post Share on other sites More sharing options...
Judge Dread Posted February 23, 2014 Share Posted February 23, 2014 Having read Alex's question more closely, I would like to wire the transformers to a single mains socked which wpuld then be plugged in. How do I do tjis safely? I think he should get hold of a local electrician and explain just what it is he wants to do and act on his(or her) advice. Here is a classic example of the benefits of membership of a local model railway club or society, where he may meet such a person. Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted February 23, 2014 RMweb Gold Share Posted February 23, 2014 Having read Alex's question more closely, I think he should get hold of a local electrician and explain just what it is he wants to do and act on his(or her) advice. Here is a classic example of the benefits of membership of a local model railway club or society, where he may meet such a person. Isn't that pretty much what I said in reply 10? Andi Link to post Share on other sites More sharing options...
peach james Posted February 24, 2014 Share Posted February 24, 2014 I have to agree with Andi, if you are asking how to do this, then probably you shouldn't be doing it without someone else's supervision. Over here, at 1/2 the voltage, I have done a few spectacular things... and I'm licenced to 600V AC ! (mind, at 3.5 MW available...) There are several possible oop's possible- and some of them end up with you being part of a live circuit, which is bad. James Link to post Share on other sites More sharing options...
Gordon H Posted February 24, 2014 Share Posted February 24, 2014 If you go this route, I strongly recommend that all of the plugs from transformers are taped to the extension sockets. Unplugging one transformer while the others are plugged in can be lethally dangerous. Let us suppose 2 transformers feed the tracks (2 separate sections, controllers or circuits). If you have a short between the 2 sections or perhaps a loco bridging the break between the two, then one section can be electrically from the other. So unplugging transformer 2, means that section 2 is still live at up to 12V from section 1 and its transformer. Although transformer 2 is not connected to the mains it is still operational, taking the 12vDC feed and converting it back to 230V - which will be available for anyone picking up the unplugged plug by the metal pins. The worst you are likely to get is a nasty shock and burn, but in the wrong circumstances it could be fatal. This might be true if we were dealing with just transformers (not DC controllers). How can a DC output controller 'take the 12V DC feed and convert it back to 230V'? Having rectifiers on the transformer secondary outputs before the controller stage should prevent any possibility of track side power getting back to the mains connection. Of course, if the rectifiers fail that is another matter - then you could be dealing with a backfeed situation, the same as if there were just transformers involved. Edit.. Apologies, just seen Il Grifone's reply saying much the same thing... Link to post Share on other sites More sharing options...
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