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Power distribution for control circuits


47137

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Hoping to avoid soldering under the baseboard of "Shelf Marshes" I have made a circuit board to distribute the 12V DC supply to the ancillary circuits:

DSCF0827.jpg.c7da18d729f5e851c4a8611505d2f879.jpg

 

 

Power enters at the connector bottom right. Above this are outlets for the circuits the layout needs all the time:

1. Lighting rig, expected to be around 1.5A constant

2. Servo controller and relay driver, 1.5A surge at start-up, 60mA quiescent, more when servos move

3. Analogue controller (if fitted), output protected and unable to draw more than 1A

 

I have doubled up the pins on these connectors.

 

The middle column of connectors is for building lighting and streetlights. The three-pole connector is for an on/off switch:

4. Lighting for the chemical plant

5. Lighting for the block of flats

6. All the other lights

 

The left-hand column is for moving features:

7. A gate across the track to the tram depot, tripped by trains, about 100 mA when moving

8. A vehicle barrier across a roadway, running on a pseudo-random timer, about 100mA when moving

9. spare

 

I have bought a 12V 3A regulated power supply for the whole layout. This has its own current limiter and this will protect the wiring to the board and the board itself. I have put a pair of polyfuses for the ancillary outputs, and there are LEDs on the board to show me these are intact.

 

Clearly my items 1 to 9 add up to rather more than 3A. The lighting rig draws 1.5A all the time, leaving 1.5A for everything else. I find it difficult to plan the diversity in a formalised sort of way, but there will be delay circuit in the feed to the lighting rig. The idea is, the delay will let all of the minor circuits start up and settle themselves before the lighting rig comes on.

 

If I am to believe what I read online, a copper strip on a piece of Veroboard can carry 5A. I take this with a pinch of salt and I reinforced the connections under the four "high power" connectors. The code 60 rail is obviously over the top but it was to hand and it is easy to solder:

DSCF0828.jpg.c6cefc830947cabe028c156c14691d4a.jpg

 

This is a one-off. Usually I use a tag board for this sort of thing, so time will tell whether the Veroboard approach is a success.

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Looks nice does that. I'm a fan of veroboard and wouldn't touch tag boards. I want to have all underboard connections with plug / socket and no soldering.

 

Having the LEDs is nice touch, and I can see how that would help with troubleshooting. However, because I have rather a lot of veroboards, I don't think it's for me.

 

The doubling-up of the main distribution tracks is a good idea. I might pinch that one! So far, all my veroboards have all been single-track, but each one of quite low power being for only short track lengths.

 

I am using something 'similar' for my DCC power distribution and turnout / servo operations using veroboard and PCB connectors. Polarity is ensured (?!) using the 'back to black' philosophy. Because I have 10 baseboards (with bolted connections) I need multiple copies of each veroboard design I make, and so it becomes a bit of a 'production line' process. At least it's mostly done off-baseboard.

 

Ian

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  • RMweb Gold

One reason for me making this board is, I had all the parts to hand except the two polyfuses.

 

I am wanting to take myself towards a "system" approach to layout wiring where I put in the main elements of the control gear (pcbs, switches, track feeds) and then use made-up cable assemblies to join the dots between them. Twenty odd years ago I was making pretty cableforms and they took hours to make and were painstaking to alter.

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3 hours ago, 47137 said:

*snip*

 

I am wanting to take myself towards a "system" approach to layout wiring where I put in the main elements of the control gear (pcbs, switches, track feeds) and then use made-up cable assemblies to join the dots between them.

 

*snip*

Exactly my philosophy as well. All components / veroboards connected by plug-in cables. Makes installation a breeze, as is troubleshooting, but it does make you 'plan ahead' to an extent.

 

And don't forget to label all the plugs and sockets!

 

Here is the underside of one of my baseboards:

20190128_180407_resize.jpg.4a709210d1a47a037acd827d8a6a93bf.jpg

 

Having done 10 baseboards, some more complicated than the above example, you can see why I'm reasonably proficient with the crimping tool.

 

All the cables are attached with normal cable clips, but with the nails replaced by screws. The screws are easier to remove / reinstall and there is no need to impact / hammer the baseboard, which could cause other problems.

 

Ian

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I see the MegaPoints servo controller in the middle. If so, are you happy you put it under the baseboard? I am thinking of installing mine face upwards, hidden under a lift-out model car park.

 

I'm not sure how often I will be fiddling with its buttons after the layout is built.

Edited by 47137
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This post gives me the uneasy feeling I should be measuring and/or calculating current consumption before getting the soldering iron out.

 

5V layout electronics currently consist of an Arduino + motor shield DCC++ base unit, two Arduino Nanos for the DCC and point controllers, and three servos for the three points I've installed so far - so well within the capabilities of the 5V wall wart powering them - but I've been perpetually meaning to switch the 5V supply to the output of a converter from the 15V DCC supply.

 

Hmm. Might need to start a topic in the DCC or electronics forum asking for advice here - thanks!

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7 hours ago, BusDriverMan said:

This post gives me the uneasy feeling I should be measuring and/or calculating current consumption before getting the soldering iron out.

 

5V layout electronics currently consist of an Arduino + motor shield DCC++ base unit, two Arduino Nanos for the DCC and point controllers, and three servos for the three points I've installed so far - so well within the capabilities of the 5V wall wart powering them - but I've been perpetually meaning to switch the 5V supply to the output of a converter from the 15V DCC supply.

 

Hmm. Might need to start a topic in the DCC or electronics forum asking for advice here - thanks!

 

Well ... on one hand, I am unhappy when I see manufactured "model railway power blocks" advertised as able to handle 6A but with no internal protection for their outputs. On the other hand, I once built a layout with a series of glass fuses, these blew at the slightest provocation and I ended up wrapping kitchen foil around at least one of them.

 

I chose 250mA polyfuses, these open at 500mA and hopefully I have sized them about right for their circuits. All they really do is protect the wiring beyond them - this is very thin for some of the model lighting. As a bonus, the polyfuses will let the point servos and lighting rig stay operational if I fail to see the problem and open the associated switch.

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19 hours ago, 47137 said:

I see the MegaPoints servo controller in the middle. If so, are you happy you put it under the baseboard? I am thinking of installing mine face upwards, hidden under a lift-out model car park.

 

I'm not sure how often I will be fiddling with its buttons after the layout is built.

Your eyesight needs no checking, that is indeed a MegaPoints 12x servo controller in the photo. I have 5 servo boards (2x 12-servo and 3x 4-servo types) plus the Controller board (with Expansion board) all controlling / operating 33 point ends on my Lower Level baseboards. There'll be another 5x 12-servo boards on the Upper Level - eventually.

 

I've been a happy customer of MegaPoints controllers so far. Installation and setup is about as easy as it gets and they are good at responding to e-mails if you have any questions. I did manage to 'blow' one of the 12-servo boards by accidentally plugging 12v across its network connection, but I was given a reduced price for the replacement board using their 'upgrade' price, which was nice since it was my own fault. Yes, they are expensive compared to, say, Merg controllers that you have to build yourself, but it is a good 'system'.

 

Initial setup of each servo board entails setting the upper / lower limits for each servo, so you need sight of both the board (for the buttons) and the servo. As I have microswitches attached to the servo for frog polarity this is an important step. After that I really haven't needed access to the servo boards, except for a couple of servos where there was undue 'friction' between the servo arm and the microswitch that lead to the turnout operating correctly, but the frog being the wrong polarity. These now work properly. You also have to set the board for Master or Slave control (I use Slave as the turnouts are operated by the Controller board) and the Network ID. After that you can essentially forget them. Therefore, there isn't any real advantage in your plan for above-board access to the MegaPoints servo controller board. However, I do plan to make an 'extension' cable for the servo buttons (like the one you made, but without the LED) just for any subsequent alterations. I think a 'mirror on a stick' will suffice for the LED confirmations.

 

In case your interested, there are more photos and details at my RMWeb layout page of 

 

Ian

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The MegaPoints controllers seem expensive until you have a go at driving multiple servos yourself from an Arduino - at least in my experience. I hadn't added any physical controls for calibrating the servos - they can be set up and configured, but only by plugging a laptop into the Arduino and sending commands over the serial interface. I was proud of that at the time, but very much want the layout to be entirely independent of any PC.

 

I got a generic servo driver board off Ebay - a breakout board for a PCA9685, connects with I2C - and could not make it work right. Unless you're really into microelectronics as a hobby then the MegaPoints products have got to be good value!

 

(I am into microelectronics as a hobby, though, so will stick with homebrew electronics for now and add a configuration interface to the next iteration of my layout controller)

Edited by BusDriverMan
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I agree that MegaPoints controllers are the best / simplest solution for the larger layouts (I have 33 point ends and will have closer to 80 when complete). If I only needed a single board, I'd probably try a Merg servo controller, but for multiple boards I'd stick with MegaPoints.

 

I'm considering using the Merg #57 board 'DCC District Cutout (DCO) Module' for short circuit protection. I'm currently using an NCE PowerCab with built-in protection, but it would be nice to have the layout in Districts each with a #57 to protect it.

 

Ian

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I am completely happy with my MegaPoints equipment so far. I am going down the route of attaching their separate relay driver and relay boards for the frogs, and I have spent about as much money on all this and the servos and their bracketry and piano wire as I might on eight Cobalt stall motors.

 

Now, this is not "cheap", but the future looks good - I have some spare channels to control the points on an adjacent fiddle yard if I ever build it, I have my simple route-setting board, and one day I can ditch my local lever frame and route setting for remote control over the three-wire bus. It all seems nicely adaptable to me. I hadn't actually heard of their 4-channel servo controller when I started - this would have saved me a few pounds but my route-setting board would not have happened.

 

I suspect the MERG system would serve me well, but to be honest I was rather sold on the MegaPoints system by their demo at Ally Pally. This was immediately after I wired up my main baseboard using a home-brew system using a Bluetooth relay board. I was so pleased with this at the time, but five years on I could rewire this baseboard for Megapoints (nine Tortoise motors) without feeling I had wasted my efforts.

 

From a personal point of view I would not entertain using an Arduino to drive multiple servos unless I could buy a unit already set up with a guarantee. The thought of needing a laptop to set up the servos using the serial port fills me with dread! Life is too short - I'll keep my Arduino for something I cannot buy, perhaps a train describer.

Edited by 47137
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I see you are definitely a MegaPoints convert. I was also sold on their system upon seeing it at model railway exhibitions, plus their YouTube videos. However, I'm also a bit of a cheapskate, and make as much of the periphery bits as possible myself, although I do use their piano wire. I use off-the-shelf servos and microswitches for the turnouts & frog polarity. The servo brackets I use are those shown in MegaPoints videos using U-shaped aluminium profile. This keeps the price per turnout 'reasonable' and much less than a Colbolt or similar. I not a fan of Colbolts simply because they take up a lot of vertical real estate that I don't have on a multi-level layout.

 

The 4-servo board is about 50% of the price of the 12-servo version, so not competitive on a cost-per-turnout basis. However, it's useful where you have small islands of turnouts. I my case, because I have a lot of baseboard joints, I try to minimise the number / type of jumper cables necessary, and a 4-turnout island would need a 12-wire jumper to the servos. That's not happening.

 

Ian

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On 11/08/2020 at 18:44, ISW said:

Exactly my philosophy as well. All components / veroboards connected by plug-in cables. Makes installation a breeze, as is troubleshooting, but it does make you 'plan ahead' to an extent.

 

And don't forget to label all the plugs and sockets!

 

Here is the underside of one of my baseboards:

20190128_180407_resize.jpg.4a709210d1a47a037acd827d8a6a93bf.jpg

 

 

I see you are organising the track feeds, servo controls and control bus into separate groups of wires. I have read about servos twitching from electrical interference, I have no idea how to trigger this but your wiring looks like good practice to me.

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2 hours ago, 47137 said:

 

I see you are organising the track feeds, servo controls and control bus into separate groups of wires. I have read about servos twitching from electrical interference, I have no idea how to trigger this but your wiring looks like good practice to me.

Thanks for the complement. It was a case of trying to be logical in the wiring to aid troubleshooting, and to have separate circuits for adding short-circuit protection later.

 

I've not experienced servos twitching at all, so either I was just lucky or I having the separate wiring helped.

 

Ian

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Ah, there was a long discussion about servo twitching I read recently but can't remember where. One solution / mitigation was firstly to lay out separate kinds of wires separately in an orderly way as ISW has done, and to glue a strip of aluminium foil to the board behind the servo wires, connected to the servo ground at one end. I think.

 

Inspired as always by how organised your wiring is!

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