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 Following on from the station lights blog I published awhile ago I have now have the lights coming on automatic when a train comes into any of the four tracks using a Arduino Nano As I have some spare Ezybus boards I used one of these to do all my connections to the Nano, it also has a 12 Volt input to power the Nano As my layout is DCC I am using a MERG PMP7 for train detecting, which uses a opto-isolator, to control the LED on the control panel. One side has a voltage on, in my case 5 Volts with a dropper resistor which brings it down to about 3.5 Volts, the other side is connected to ground 0 Volts. One of the Nano pins reads this voltage, if it is 3.5 volts it does nothing but if it at 0 volts it switches on another pin on the Nano. I have used 4 PMP7's for the 4 tracks and used 4 pins on the Nano ( one for each track ) if any of the pins goes to 0 Volts it will switch on the output pin, this in turn switches on a replay to power the LED's ( I have not used the output pin ...

 A few months ago I produced a batch of Ezypoint kits for our local members to overcome a shortage in the Kitlocker.  At that time the kit was produced on stripboard which some members find problematic. An additional PCB board normally available from MERG was not available either.  Alan Turner ( the PCB designer) had only a few boards available but graciously provided me with the gerber files to allow me to order PCBs directly from China . Having sourced all necessary components, the kits were duly made up. I find this simple kit is really useful for automation projects. A toggle switch provides either a HIGH or LOW on the PIC input pin to determine which of the two servo positions is selected. For a particular application, I wanted to use a push button to toggle the position on alternate presses of the button. This involved a rewrite of some of the code in the PIC. I initially developed the program using an Arduino as a means of testing the logic. When this was successfu...

 Today's West of Scotland talk was on Solenoids. Soenoids are still extensively on some model railway layouts. H&M, Peco and SEEP are common manufactures. Some early controllers have a 15v ac supply which can be used to operate the solenoid. Push buttons or passing contact switches are normally used to operate solenoids due to the large  operating currents involved. These passing switches are expensive at around £9 to £16 for every single point. With the voltage drop across the solenoid a higher voltage is sometimes used supplied by a Capacitor Discharge Unit (CDU) The circuit of  a typical Gaugemaster CDU was discussed costing around £15.  Davy then showed us an equivalent Veroboard version for around 71p that would work with a centre off SPDT switch.  The MERG dual CDU version using a simple on/off switch uses a circuit that operates the solenoid and charges the opposite direction capacitor at the same time. If this unit is placed near the point only a sin...

 This evenings Virtual Area Group meeting covered what needs to be done when your MERG Kit does not function after assembly. Simon West was our presenter and informed us that almost 90% of problems is down to poor soldering techniques. A timely article from Martin Perry has appeared in the December Journal and is well worth reading. Make sure you have done all the preliminary tests as outlined in the building instructions. DO NOT plug in IC's until these tests have ben completed. It is essential that the orientation of components is checked before applying power to the circuit. This is essential for diodes, electrolytic and tantalum capacitors. Fault finding needs a logical approach and you should note down your results as you proceed. Have a reason for doing the test and refer to the circuit diagram. A basic multimeter is essential and does not need to cost a fortune. (About £3.50) A very decent version is available for under £20. Do not be afraid to contact other MERG members. Th...