RobertW

When I'm wiring a layout, the easiest way I find it to create a defined main route, for example I have a small inglenook style layout with a cable route running around the edge of the underside of the board for all wires, and then wires running perpendicular to this to where they need to go in the middle of the board. For points I use a 7 wire loom with 4 for the solenoid coils and 3 for the point position switch. All of the track feeds come to a terminal strip and then radiate out to where they are going. I started by using cable markers, but gave up when I rewired a few systems. I use cable tie bases, but if I was to do this again I would run a piece of cable trunking down the board and then exit to make connections (either white minitrunking with holes to allow cables to enter and exit, or I would use slotted panel trunking which is expensive but makes this easier). I lay the cable tie bases first in the route I want to take, and then run the wiring along the route and cable tie them in. You can see in this shot of one of my train detectors how the main bundle of cables runs along the timber to the left. This contains wiring for track, points and accessories. At some point I will go through and label all my wiring, but I do know what all of the connections do so I'm not too bothered. Hope this helps, Rob

Hi Junctionmad, My take on it was that by arranging it so that the LEDs are controlled by the direction switch SW2, they will reflect the actual position of the tiebar, rather than the intended position as it's a PL-13 SPCO switch mounted on the motor. I've had a similar application on a previous project where the LEDs were controlled by a 555 bistable with a DPCO non maintained switch ganged to the point motor switch. If the point didn't move for some reason, the LEDs were out of sequence with the point position, hence why I'm basing it on the mechanical movement of the point, rather than the electrical control pulses to the point. Hope this explains things a little. Thanks Rob

Hi All, Just for completeness, I redesigned the module to Andy's suggestion, and it worked perfectly on breadboard. I've attached the updated schematic, and I'm moving on to produce the Veroboard this weekend. The way that I've implemented the slugging is to maintain the supply to the transistor as suggested through a 470μF capacitor. I did try to slug the relay coils, however I found it more effective this way. The result is that the move is completed properly, as the motor remains energised for longer. I'm now at the Veroboard design & manufacturing stage, as there will be 4 of these for my new layout. I'm hoping to start building the baseboards next weekend, and I'll start a layout thread in due course. Let me know if you have any comments. Thanks Rob

Hi Junctionmad, When I push the push button, the point tiebar moves across. The test rig I have has an ordinary microswitch recovered from a mouse with the end of the tiebar actuating it at the end of the travel. As the tiebar releases the microswitch, the relay controlling the solenoid drops out before the tiebar has overcome the spring in the point, which causes the tie bar to move back across into the microswitch, starting the cycle again. Looking at the diagram, I think I might end up needing a microswitch at each end of the tiebar, and just using the N/O contacts on each microswitch to actuate the relays. Thanks Rob

Hi John, That's fine. It occurred to me tonight that there was a better way of doing it. If I use latching relays instead and fire one coil with one way on the PL-13 and the other coil with the other, then only when the PL-13 has moved over will it try to fire the other coil. I need to order the relays as I've only got non-latch ing ones in stock, and I'll update when I've got some news. Thanks for your help. Rob

Hi John, Thanks for this, its been really useful. I've updated the design as below. I think that the way you could mitigate this would be to fit 2 electrolytic capacitors as per the diagram to sustain the voltage for a small time after the switch moves, and arrange the time constants for the circuits such that the relays won't change until twice the time that the solenoid control line is energised for. This means that hopefully the point won't oscillate. The CDU has 4000µF of capacitance so it should have a discharge time constant of 16ms, and a discharge time of 80ms. The solenoid should be energised through the capacitor C2 for 558ms, meaning that the CDU should be completely discharged through the motor by the time that the capacitor C2 is discharged. To prevent the point oscillation, the direction control is delayed by 1.65s, meaning that the relay shouldn't switch to the other transistor base before the CDU is fully discharged, hopefully fixing the oscillation. Let me know what you think. Thanks Rob

Hi All, I'm currently designing the electrics for my new layout. I'm aiming to switch the points using a custom point controller. The aim is that the front panel will consist of a single push to make switch per point, with 2 LEDs to indicate the direction of the point. The circuit will also be able to work with live frog points. I am using a Peco PL13 switch to switch a pair of DPCO relays in parallel (in that the relays switch together to form a PCB mounted 4 pole changeover relay). The first contact is the push button switch, which can be switched through the relay to the base of one of 2 power transistors depending on the lie of the points. The second changeover contact switches between the pair of LEDs, so that the indication is of the actual position of the points. On the second relay, one set of contacts switches the polarity of the point frog, and the second is spare. I've built this on a breadboard, and when I push the button, the point tie bar on my test bed rattles across between the 2 positions. I thought that perhaps the control voltage was dipping when the points were being switched, so I've tried using a high value capacitor to hold the 5V up while it switches, however it still does it. I'm feeding the CDU from 24VDC from my bench power supply with a 5VDC feed from the bench power supply to the control side. Can anyone suggest a solution to allow the point to change from one direction to the other when the button is pressed. I'm trying not to use ICs, and I think that the circuit isn't far off, but its not quite working correctly. Thanks and apologies for the wordy post. Thanks, Rob Point_Controller.pdf

Hi, I think that the reason that the lights get dimmer as the ambient light level falls is because Light Dependent Resistors tend to have a response where their highest resistance is when it is dark. You could get over this problem with a LDR in a potential divider. LDRs typically have a light resistance of about 8k, and a dark resistance of about 1M. From experiments, the best way to do it is with NPN Darlington transistor arrangement. This gives a sharp response between on and off, as Mark says, it's rare for the lamps to come from low brightness to high brightness, its more typical to be on or off. The LDR forms the bottom of the Potential Divider between the base of the transistor and ground, with a 1M resistor between the base of the transistor and supply. I've attached a sample circuit diagram. The supply voltage is uncritical, so it could be fed from a rectified 16VAC supply from the controller. If you wanted a manual override, you could connect a switch across the collector and emitter of Q2, which are pins 2 and 3. Let me know if you've got any comments or questions. Thanks, Rob

Not be pedantic, the cabinet with the yellow stripe is a FSP (Functional Supply Point). These come under the Electrification and Plant branch (although are subject to the same standards as signalling equipment), and are a sub-distribution point for the Signalling Power supply. There are multiple FSPs on a feeder, and Feeders can either be single ended radials (used for branches and sidings) or on double end fed feeders between Principal Supply Points. Further details can be found here under PowerU FSP01/02, FSP03, FSP04. Hope this helps, and please let me know if you have any questions or comments. Rob

Hi, I'm currently using AutoCAD Electrical 2018 to do various 2D drawings for my railway, mainly electrical schematics and 2D orthogonal drawings for buildings and veroboard layouts. I got it when I was a student on a 3 year licence, which expires in September. I'm starting to look for a replacement for it, that is preferably either free or has a one off fee rather than a subscription. It would need to be able to import Autodesk DWG/DXF file types as I have a number of CAD files that I've built up over the years that I would rather keep rather than redraw. I also have Autodesk TrueView, so it isn't too onerous to covert files. I'm not too fussed about 3D modelling, although it would be nice to have if possible. Does anybody have any suggestions I could take a look at? Thanks Robert

Hi, I've recently purchased a Hornby Jinty, and I'm going to repaint it as an industrial loco. I've done some google research, and I've seen the Crigglestone one by Paul Lunn, and the W.Pepper & Sons that Bachmann have done, but are there any other well known industrial liveries that I could use. My microlayout is set in the Manchester area if that helps. Thanks, Rob

Hi All, I'm currently designing an LM317 based model railway controller for a shunting layout (essentially just using the standard LM317 circuit with the resistors trimmed for a maximum of 9V). I'm trying to add inertial simulation to the controller, but I'm not sure how would be best to do it. On previous controllers where I'm using a Darlington circuit, I can add it to the base of the Darlington. It occurred to me that I could add a capacitor between the adjustment pin of the regulator and ground it would gradually decrease the voltage on the adjust pin, which would then lower the output voltage slowly as well, but this would be harder to control in terms of the amount of inertia provided and it would possibly have to be quite large to sustain the inertia. Does anyone have any suggestions on how to use an inertial simulation element with an LM317 regulator. Thanks, Rob

Thanks for this input. I hadn't considered using 74XX circuits, because if I'm building a module, I generally don't have enough circuitry to use up all of the gates, and I don't like wasting the rest of the chip. On this project, I've managed to use up all the chips. I'll post the new schematic tomorrow, and I'm going to breadboard it tomorrow as well. Thanks for your help. Rob Track_Circuit_Veroboard.pdf TrackCircuitSchematic.pdf

Just an update on this, I've solved the issue. It was due to inverting the potential divider R2-R3. I've attached an updated schematic to this post, including the integral power supply and track circuit. It's designed to be fed from the 16VAC layout auxillary system. I've designed this circuit for use with Train-Tech signals, which are common ground, hence the need to convert the driver to Common-Cathode. The circuit designs is based on Roger Amos' design for a signal driver and bi-directional track circuit, however, I have converted it to Common Cathode, as well as incorporating manual override. Whilst the drawing denotes the functional blocks of the system, the boards are integrated, with a track circuit, signal driver, and AC/DC converter on 1 veroboard. Please let me know if you have any comments. Thanks, Rob Signal_Driver_Rev_C.pdf

Hi, I've redrawn the schematic in Eagle. Please see attached. Thanks, Rob