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Fulgurex point motor control

22526 Views 70 Replies 13 Participants Last post by  dwb
This week's project is to add control circuitry for a Fulgurex slow motion point motor. The photo below shows the parts I intend to use:

Those familiar with driving Fulgurex will probably think this is a bit over the top, but there is method in my madness and each component has its place in my scheme.

First, it is my intention in the longer term to drive the point motor via DCC, but there may be times when I don't want to have to go to the bother of addressing the motor via the control unit and then selecting the direction I want. To avoid that, I need a local switch. Some DCC point motor controls provide a facility for local buttons, but I'm not sure which those are and whether or not I will use them. In the meantime, I need to control the motor now because unlike Peco solenoids, you can't manually "flick" a Fulgurex. My solution to this need is to use a normally open, momentary action DPDT switch which can be seen in the left of the photo.

The momentary nature of the switch means that once the limit has been reached and the current is switched off, I can release the switch and there will be no current at all. This should avoid conflicts with any DCC control unit I install later. The drawback with this method is that I lose the switch acting as an indicator for the current setting of the point blades. The solution to this problem is to use one set of auxiliary contacts on the Fulgurex to drive the pair of LEDs which are also on the left along with the resistors and matching mounting bezels. This will provide a visual indication by the switch of the current setting. When DCC control is added, any changes caused by the DCC unit will be reflected by the LEDs. This circuit may also double up as input to a pair feedback sensors to provide PC control some time in the distant future.

The ceramic disc capacitor at the bottom of the photo is to provide a degree of noise suppression. According to LDT, the Fulgurex is rather "noisy" electrically and this is a good precaution. Once the motor is installed under the baseboard, I don't fancy lying on my back trying to retrofit these things later, so they're going in now.

The other two devices beside the capacitor are a pair of Zener diodes. This again is an LDT recommendation for reducing the voltage supply to the motor to reduce the change over speed. I'm doing this because the motor will be supplied at about 14v DC which is a bit on the high side.

I will be using the other pair of microswitch contacts to change the frog polarity on the point. The switch blades themselves are hard wired to the outer rails. This eliminates the potential for shorts should the microswitch change over before the moving point blade has ceased making contact with the outer rail. A short on an analogue DC layout is no problem, but it will shut down DCC which is not a good thing.

The black stringy stuff in the top right is heat shrink tubing which I will use to make sure there are no bare wires straggling about.

Now I just need to find something to mount the switch and LEDs on. Panel thickness is a bit of an issue for these LED bezels because the LEDs are quite small.

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>I have found some cable with 8 bound wires 0.22mm² that will go to each point. Power will come to the panel and the wires will take power to the point and send back switch status to the LEDs. I was using Ethernet cable, this new one will hopefully be a little easier to manage.

That's an interesting idea. I have my point connections down to 4 wires - 2 for the directional power to drive the motor and 2 to return the output from the point setting sensors. The signal being switched by the sensors is sent direct to the sensor switches on the points.

Since my layout is permanent, I don't need to have "instant" connections on the back. I did consider some 36 way connector plug/socket combinations but once you factor in the cost of buying the pins the cost escalates rapidly.

I do like the idea of using Ethernet twisted pair cable to create a wiring set for a point. You could mount a patch panel on the rear of the control panel and swap to your heart's content. In fact if you made a generic panel (ie no track diagram) with a bank of switches and LEDs you would have something eminently reusable.

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I made the last connection on the panel this evening. I have checked the LEDs are working using a wandering lead from the power lines and they are all ok. Tomorrow evening I will make a tester for switch circuits and while I'm testing, I'll charge up my camera batteries to post a couple of photos.

Some statistics to close:-
180 screw terminal connections. Each connection took about 10 minutes each. I have consumed about 8.4 metres of heat shrink tubing.

QUOTE (dwb @ 23 Apr 2007, 22:23) <{POST_SNAPBACK}>Some statistics to close:-
180 screw terminal connections. Each connection took about 10 minutes each. I have consumed about 8.4 metres of heat shrink tubing.

Now that's what I call committment...look forward to seeing the photos.


I have completed testing the connections. There was one dud solder connection on the back of a switch, all the rest were ok.

I did post the connection diagram but in the wrong thread, so I am reposting it here for completeness:-
Rectangle Slope Font Line Red

This connection diagram has worked out really well. I recommend this as a labelling method.

Here is the completed panel:-
Ring binder Font Wood Parallel Engineering

and this is what it looks like if I "fake" a few connections. I've set a route from the goods yard (lower left) to the "down main" of the upper junction (upper right)
Font Electrical wiring Parallel Engineering Electricity

The yellow LEDs are occupancy detectors. The red LEDs are point settings. The blue LEDs show that electric uncouplers are active.
and finally, this is what it looks like from the other side:-
Circuit component Amber Electricity Electronic engineering Gas

Believe it or not, there is a colour code here:-
Red = 12vDC
Black = 0vDC
Orange = signal which means either 12v or 0v

That's where all the heat shrink went.

The next stage is to mount the panel on the baseboard, having worked out how to fold it carefully without breaking anything.

I think it's time to join the MERG so that I can make use of their DCC related circuits. There are 35 points on this panel and I need some occupancy detection too.

The next time I do this (there are at least three panels to be done in the future), I will make the following changes:-
1) Use a smaller gauge wire for the LED circuits. The current is about 10mA, so the wire can be a lot smaller.
2) Make room for switches to control signals



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That looks fantastic David - looks really professional & neatly done too.

Thanks for posting the pics & keeping us informed of the progress.
Thanks for posting the pix David - it's a very impressive piece of work of which yoy should be justifiably proud.


Thanks for the kind words guys.

This is another of those tasks where you know that each time you make another connection you are nearer the end even though it seems unreachable. Now that I am there, it feels a bit of an anti climax.

> What are the blue leds for David?
To tell me that I have switched on a Kadee electromagnetic uncoupler. The switches are DPDT; one pole switches a hunky relay which provides power to the uncoupler coil - 3 Amps according to the instruction sheet!; the other pole lights the blue LED. The blue LEDs are very bright. I think I will reduce the current through them next time by using a larger series resistor next time.

A bit late in responding I know, but ref post #54 and how to transfer a layout plan to a sheet of metal.
I saw a U-tube vid recently about making PCB's and the guy there downloaded his PCB scheme from the net and printed it onto photopaper (he used Staples own brand) and then ironed it onto the pcb using max heat setting and much pressure, before etching.
Try the same thing for your panel but mirror the layout before printing so it irons on the right way round - and don't let domestic management find out you b*ggered up her best steam iron.
An interesting idea. I might manage the steam iron bit but what about the etching? Take it to a local PCB house and ask if they'll dunk it in something nasty for a fee?

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