Skip to main content

Solenoids

 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 single wire is required to operate  the control relay. This kit is available from the Kitlocker in two versions, PD3-1000 at £7.73 or PD3-2200 at £8.15.

A single circuit version was demonstrated that can be built for around £1.34 on veroboard.

Another version currently under development was shown which used high power MOSFETs  to replace the transistor relay combination. Hopefully this will be the subject of a later talk in the New Year.

The circuit diagrams for these units are available from Davy Dick.

Over the next couple of weeks the video for this talk will be available on the West of Scotland web site

Keith Shovelin then demonstrated a programmable flasher that uses existing PMP kit 21 Dual Flasher and PMP 20 Versatile timer. 

The versatile timer utilises a 5V supply for the controlling PIC. The NE555 of the Dual flasher uses a 12V supply and the two are not compatible. A non inverting  Optocoupler ( see Chapter 18 of Davy's book available on the MERG website) is used to interface the two circuits.

The circuit for this again will be made available on the WOSAG site. An alternative would be to redesign the Dual flasher to work on a shared 5 volt supply.

As usual, a well attended and interesting talk.

Labels:

Comments

Post a Comment

Popular posts from this blog

Train sequence / timetable using Arduino

                              Following discussions in a MERG Zoom meeting about potential projects for the Cumbria virtual area group I have started this blog to share my ideas for building a train sequence / timetable system based on an Arduino UNO. The trigger for this project was Andy Robb's article in the MERG journal (June 2020 edition). In it Andy describes using an UNO with a OLED display to produce an electronic station display board.  Having tried out Andy's version I started thinking about expanding the idea and have come up the following list of possibilities: 1. Replace my card index train sequence with an electronic version. 2. Have the train sequence synchronised with the on platform displays. 3. Display an analogue clock on the station display and have it display the train times. 4. Store the position reached in the sequence so that it starts where it left off on power up.  To mak...
8 comments
Read more

Push button Ezypoints

 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...
Post a Comment
Read more

Cumbria Group Meeting Friday 9th October

 Although this was only a coffee and chat meeting, eleven members joined us for an interesting session which basically covered what was on our workbenches. Some members suffered from technical gremlins on the Zoom session but hopefully they will have that sorted for next time. Andy Woolass had volunteered to be a guinea pig for building the latest version of an EzyBus Input Module. It was a fairly straightforward build but the lack of sufficient ground points for external connections was a suggested improvement. The original Input board which used an MCP23017 Module was originally supplied by Davy Dick for £2. Members trying to build their own using a provided PCB, sometimes fell foul of the different form factors of this Module which caused obvious fitting problems. It is for this reason the PCB has been redesigned to accept a more standard 28 Pin DIL device. The Kit will be available in the Kitlocker, but at £7.20 it is a little expensive. Various members showed Arduino developme...
2 comments
Read more