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Route-setting panel for MegaPoints servo controller


47137

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The MegaPoints servo controller has three memories to provide for simple route setting. I have built a small switch panel to let me use this functionality.

 

Operation of the memories uses push buttons (to be provided by the modeller) with visual confirmation from an LED mounted on the servo controller. To my mind, any kind of reasonably ergonomic operation needs sight of the LED, so I modified the servo controller to drive a new LED beside the push buttons. This probably voids the warranty but I think the modification makes the project worthwhile.

 

The on-board LED is the one labelled MODE and it has a dedicated voltage-drop resistor marked 1001 meaning 10k ohm:

P1020228.jpg.80124a5588f37c478043ea8700339f8e.jpg

 

When this LED is lit, the voltage drop across its resistor measures 2.6 volts, suggesting a current of 2.6 mA. I cannot work out for certain what is driving this LED but it might be the CMOS octal register nearby - such a device could sink 4 mA on one of its outputs. It seems prudent to leave the current consumption much the same (or less) so I disconnected the on-board LED by lifting one end of its 10k resistor. This is easier than trying to lift the LED, and the resistor is still there if I ever want to put it back. I bought a high-efficiency LED and connected this (with a new 10k resistor) to the two 'via' holes beside the on-board LED:

P1020246.jpg.47b3d36aa97f0300f14d28f12ce23d74.jpg

 

I rather like these servo-style connectors. If you plug the mating connector in the wrong way round, you just swap it around to make the LED light up. I put the new resistor on my switch panel, beside the new LED.


My switch panel is a scrap of Veroboard with four pcb mounted switches. These are momentary action switches. When you push a switch, it connects the pair of pins on its left (always the common on my board) to the pair of pins on its right. The copper strips are running vertically in this photo, and the connections from the switches are fairly easy to understand:

P1020248.jpg.44bd1cf63fce4282f470f93e949abff5.jpg

 

For operation, you set up a route on the servo controller and then press and hold a 'route' button until the LED flashes three times and goes off. This response from the LED shows the route is stored in the memory. You can then proceed to operate the layout as normal, using the servos to set a different route. A short press on the same button recalls the memory, sets the servos to suit, and causes the LED to light constantly. A short press on the reset button extinguishes the LED and restores normal operation of the servo controller.

 

I am left-handed so I have indulged myself by putting the LED where I can see it when I press any button. I chose yellow for my LED because I prefer to keep red (as used for the on-board MODE LED) to show fault conditions.

 

P1020247.jpg.c751edb34c424d3886517f1bedaccb37.jpg

 

I bought a 50 x 50 mm sample of acrylic sheet to make a small escutcheon / panel. This seems an economical approach, there is no waste and the functionality here doesn't lend itself to adding in beside a lever frame.

 

I trimmed the Veroboard and added some strip wood to hold the panel:

P1020291.jpg.c459d461ac34dc14cdb97a34bb89fcda.jpg

 

The finished panel looks like this:

P1020294.jpg.461ae9b01fd4340778ba497e21fa9678.jpg

 

I chose a matt acrylic colour called "Grey Ash". The LED is flush with the panel and the buttons are about 2 mm above it.

 

Eventually I made up a cable to connect the wanted pins on the panel to the servo controller. I ended up doing this about four times over but this is the final version:

P1020313.jpg.68a06537bf9c61ca7c7c7b32b6f19a2e.jpg

 

I started with 7/0.2 wire and this left the terminals too fat to go into the housings. Trying with 7/0.1 wire I still made many many crimps wrong and I probably discarded thirty before I had 14 I was reasonably happy with.

 

My ribbon cable is about 0.9 m long. There is no specification for the maximum length of such wires in the MegaPoints documentation, but I had 1.5 m of ribbon cable and I wanted to leave myself with a usable offcut.

 

The nearest terminal labelled SC is free for use with the local point levers (switches) on S1 to S9. I am keeping S10 to S12 free for future use if I connect a fiddle yard directly onto the layout.

P1020316.JPG.668b9fa68cb1de77b8f3dee71b185644.JPG

  • Craftsmanship/clever 3

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Richard,

 

Nice bit of work / hacking there. Unfortunately I can't see how I can use the Memory features as I have 5 servo boards controlled by a central MegaPoints processor (which doesn't have the memory functions). I'd like to have some 'route' functionality, but it looks like I'd need to use multiple servo boards to create a route. I suppose I could invest in the MegaPoints 'route processor', but if there is a homemade method I'd be very interested.

 

I understand the idea behind replicating the LED on your veroboard, but why didn't you simply add a second LED in parallel with the one on the board? Then you could have used the existing Mode / Common plug on the servo board for the Mode button.

 

I hope you'll go back and put some heatshink on those soldered connections ...

 

For all my MegaPoints cabling I use a 15ft 6-core ribbon cable from HobbyTronics (ref: CAB-10646). It's cheap at £2, flexible,  and when split into 2x 3-cores gives colours suitable for servos (brown / orange / red) and network (blue / green / yellow).

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  • RMweb Gold
2 hours ago, ISW said:

Richard,

 

Nice bit of work / hacking there. Unfortunately I can't see how I can use the Memory features as I have 5 servo boards controlled by a central MegaPoints processor (which doesn't have the memory functions). I'd like to have some 'route' functionality, but it looks like I'd need to use multiple servo boards to create a route. I suppose I could invest in the MegaPoints 'route processor', but if there is a homemade method I'd be very interested.

 

I suspect you will have to get the route processor, or possibly some kind of third-party item connected to the bus.

 

I am using my servo controller in its master mode, i.e. the servo controller is taking its instructions from its row of input pins and is driving the bus. I know this because I have hooked up a MegaPoints relay driver and this is responding to commands over the bus from the servo controller.

 

I don't have a Minipanel or Multipanel, but using one of these will need the servo controller to be controlled through the bus. This will disable the twelve inputs S1 to S12, and by extension I suspect it will disable the controls for the three memories. I don't see how they can "work" this way.

 

The only homemade way I can imagine using a Minipanel or Multipanel would be to drive the bus from something like an Arduino, and use this to store a selection of routes and recall them at a push of a few buttons. Arguably, when you are writing the code you could simply define the bytes to write to the bus to set the servos as wanted. I get the impression, a Multipanel would respond by changing its LEDs to match the route, but I haven't fathomed out how or if the Minipanel copes with having other devices driving the bus.

  

2 hours ago, ISW said:

I understand the idea behind replicating the LED on your veroboard, but why didn't you simply add a second LED in parallel with the one on the board? Then you could have used the existing Mode / Common plug on the servo board for the Mode button.

 

I disconnected the original LED simply to limit the power I was drawing. I have no idea how much current the board can supply, but the board was quite expensive to buy and I didn't want to be asking for a manufacturer repair because of my hacking.

 

As far as I can see, the Mode LED has one of its leads connected to the positive rail and gets lit by taking its other lead to 0V. This makes some sense - it's usually easier to sink than to source current from an IC. The switches work by connecting an input to ground, so I have to take two wires across to the new LED.

  

2 hours ago, ISW said:

I hope you'll go back and put some heatshink on those soldered connections ...

 

I'd like to make up some new leads. Maybe one cable for all seven wires. What I'm not sure about is where to put this little panel. It might be good a metre or so away from this baseboard, nearer to the controls for the rest of the layout (this is a wall hugger). Obviously I need to be near the baseboard for shunting, but if I wanted to simply extract a train I might do this from nearer the other end of the layout.

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48 minutes ago, 47137 said:

 

Are you using a crimp tool to make off the leads? If so it would be good to know which one.

Richard,

 

The crimping tool I use is an SN-28B I got off TheBay 2-years ago. Details below. A quick search of said TheBay reveals it is still available from a number of UK suppliers, although not the one I used back then. The smallest jaw fits the 6-core cable I mentioned and 7/0.2 wire I use for track droppers. The 2nd jaw fits 16/0.2 cable I use for 'distribution cables' off the power bus cable. It's not a very expensive version, but has served me well for the last few years.

 

The crimp connections (CRIMPPINS), housings (CRIMPHOUS2 & CRIMPHOUS3), and headers (36HEAD) I get from HobbyTronics (just a customer). 

 

If you look through my layout (Burton-on-Trent South) you'll see it has gotten quite a lot of use, as I use PCB connectors for just about everything! The following link is a good example. 

 

Ian

 

 

981874298_18-09-20-CrimpingTool_Page_1.jpg.2132e96fc40899c5994c9f463cf67120.jpg

 

1651432595_18-09-20-CrimpingTool_Page_2.jpg.1a948214bbc5c743f7a16f25ee708fcb.jpg

Edited by ISW
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54 minutes ago, 47137 said:

 

I have ordered up a boxed set containing a crimp tool, some ribbon cable and 1500 crimps. Should keep me out of mischief for a while :-)

Richard,

 

Did you get some male, as well as female, crimps? They are really useful for making up 'extension leads', which I tend to use for servos where the cable is never long enough.

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  • RMweb Gold
On 28/07/2020 at 09:12, ISW said:

Richard,

 

Did you get some male, as well as female, crimps? They are really useful for making up 'extension leads', which I tend to use for servos where the cable is never long enough.

 

Yes - see my comment on 31 July.

 

I am wondering - suppose I use some solid copper wire for the droppers from the track, if I choose a suitable thickness I could slip a female crimp over the wire. No soldering under the baseboard and I can pull the crimp off the dropper If I need to find a short circuit.

Edited by 47137
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9 hours ago, 47137 said:

 

I will report back here when the box arrives.

 

I am wondering - suppose I use some solid copper wire for the droppers from the track, if I choose a suitable thickness I could slip a female crimp over the wire. No soldering under the baseboard and I can pull the crimp off the dropper If I need to find a short circuit.

Richard,

 

That's an interesting idea I'd not heard of before. It's not one I'd use as I follow the method used on Chadwick Model Railway (there's a YouTube channel) whereby you drill one hole on the track centreline and both wires use the same hole. I think I'd get a short if I tried that with solid copper wire. Yes, I could use insulated solid copper, but I think I'd never get the wire bending right. Also with solid copper I think I'd have to solder the wires onto the rails 'after' tracklaying. I always solder the wires to the underside of the rail before tracklaying as my soldering is neater (and quite well hidden) that way.

 

To reduce soldering (apart from to the rails) I use a simple 'distribution' veroboard for multiple tracks on the same power circuit, as shown below (sorry the quality is not that good as it's a crop from a mobile phone picture). This is effectively my 'version' of your 'solid copper wires' / 'female crimp' idea. It's all socketted (& labelled) so troubleshooting is relatively painless.

 

20190208_195558a.jpg.d915c6e80e3ea3da3f44f65aa9fe825a.jpg

 

Ian

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  • RMweb Gold

Verobard and Dupont connectors go together perfectly for this sort of thing, and a whole lot neater than a screw terminal block or a tag strip.

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  • RMweb Gold
On 28/07/2020 at 09:12, ISW said:

Richard,

 

Did you get some male, as well as female, crimps? They are really useful for making up 'extension leads', which I tend to use for servos where the cable is never long enough.

 

Yes - male and female crimps, and housings for DuPont 1,2,3,4,5,6,8 and 10 ways all with a single row of terminals. There are also 200 odd Molex connectors - pcb headers, mating plug housings and female crimps to go into them.

 

https://www.ebay.co.uk/itm/Dupont-Crimping-Tools-SN-28B-Ratchet-Crimper-1550x-Male-Female-Pin-Connectors/383593979384?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

 

The suggestion of female crimps sliding onto solid copper droppers is my idea, in that I've not read about it elsewhere. I expect I will give it a try one day.

Edited by 47137
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2 hours ago, 47137 said:

 

Yes - male and female crimps, and housings for DuPont 1,2,3,4,5,6,8 and 10 ways all with a single row of terminals. There are also 200 odd Molex connectors - pcb headers, mating plug housings and female crimps to go into them.

 

https://www.ebay.co.uk/itm/Dupont-Crimping-Tools-SN-28B-Ratchet-Crimper-1550x-Male-Female-Pin-Connectors/383593979384?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

 

The suggestion of female crimps sliding onto solid copper droppers is my idea, in that I've not read about it elsewhere. I expect I will give it a try one day.

Richard,

 

That's quite a nice kit you've found on TheBay. However, what I don't understand is their inclusion of the 'black' set (typically called PCB connectors) and the 'white' set (typically called Molex connectors). The 2 types are incompatible, even to the extend of the crimp pins. I'm guessing you'll try them both and see which type you prefer and stick with that afterwards.

 

I chose the PCB connectors as that's what comes installed on servos and is the one used by MegaPoints Controllers, which is my choice of turnout operating equipment. Oh yes, and it's a bit cheaper ...

The advantage of Molex is that it is 'handed'. You can't fit a plug the wrong way round.

 

 

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  • RMweb Gold
On 31/07/2020 at 10:37, ISW said:

Richard,

 

That's quite a nice kit you've found on TheBay. However, what I don't understand is their inclusion of the 'black' set (typically called PCB connectors) and the 'white' set (typically called Molex connectors). The 2 types are incompatible, even to the extend of the crimp pins. I'm guessing you'll try them both and see which type you prefer and stick with that afterwards.

 

I chose the PCB connectors as that's what comes installed on servos and is the one used by MegaPoints Controllers, which is my choice of turnout operating equipment. Oh yes, and it's a bit cheaper ...

The advantage of Molex is that it is 'handed'. You can't fit a plug the wrong way round.

 

 

 

I would not recommend the kit or buy it again. The dies are about 0.5 mm too narrow, so you can achieve a good crimp on the conductors or the insulation but not both. I settled for the conductors off course, and then used pliers to nip up the prongs onto the insulation so the terminals would go into their housings.

 

My rate of attrition on terminals was high and I did not achieve a standard consistently good enough to satisfy. I would not want to try making up DuPont connectors again (and ready-made cables are cheap enough), but I think there is mileage in the detachable track feed idea.

 

 

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18 minutes ago, 47137 said:

 

I would not recommend the kit or buy it again. The dies are about 0.5 mm too narrow, so you can achieve a good crimp on the conductors or the insulation but not both. I settled for the conductors off course, and then used pliers to nip up the prongs onto the insulation so the terminals would go into their housings.

 

My rate of attrition on terminals was high and I did not achieve a standard consistently good enough to satisfy. I would not want to try making up DuPont connectors again (and ready-made cables are cheap enough), but I think there is mileage in the detachable track feed idea.

 

 

I thought I might have the same issues as yourself, but I managed to find a really useful 'tutorial' on YouTube at https://www.youtube.com/watch?v=-u1t7Cdf6RE that really helped. I suggest you give it a watch as it may help solve your issues.

 

One of the 'tricks' is to make sure you only strip ~3mm of the wire for the crimp. Too long and it fouls the connector area. Then to find a way to ensure you insert the cable by the correct length. This took me a bit of trial and error, and I had to cut off the faulty crimps.

 

Ready made cables are an alternative, but they are never the right length; too short and you need to make an extension, or too long and you have to tie-up the spare length to keep things tidy. I haven't used any ready made cables myself.

 

Ian

 

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  • RMweb Gold

I tried to strip around 2.5 mm and this does work in that the wire stops in the right place when the insulation meets the inner crimp area.

 

This is good too:

https://www.instructables.com/id/Make-a-Good-Dupont-Pin-Crimp-EVERY-TIME/

even if the writer needed ten pages to explain it.

 

I am left-handed. I did try reversing the dies in the crimp tool but in they end I settled for them in their proper places and held the crmip tool in my right hand.

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40 minutes ago, 47137 said:

I am left-handed. I did try reversing the dies in the crimp tool but in they end I settled for them in their proper places and held the crmip tool in my right hand.

I'm left handed too and manage to use the crimping tool lefthanded. I suppose it just takes perseverance and practice.

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  • RMweb Gold

It occurs to me, if I had an unused servo channel I could connect a servo and use it as a semaphore-style repeater to show whether a route was selected. Simply include this servo with its input "on" in each of the the three routes.

 

This would save modifying the servo controller. A concealed push button switch would be useful for the input when setting up the routes. Usability would depend on how often you want to redefine the routes.

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