Steve’s been in touch – have a look at his way for detecting trains:
Detecting trains on the layout can be very useful.
I Just thought I might share this little trick that I have developed. It is a simple, cheap, and very liable method using just 3 resistors.
I use this method to:
To operate a crossing
A train position indicator
To activate an announcement or sound
The advantages of this circuit are:
- Cheap and easy to build
Works with any power mode, DC, DCC, battery etc
Can work with any power supply
Output can be adjusted to interwork with any other device
Small current drain
Take two ‘light dependent resistors’.
One is placed under the track (r2), and the other (r1) is placed anywhere alongside the track. Connect the resistors together.
Connect voltage to the other side of r1. Connect the centre contact of a 50k variable resistor (trimpot, r3) the other side of r2.
Connect 0v to one side of r3. Adjust r3 to achieve the required output voltage from the centre connector.
All of these devices are simple, cheap, and can be obtained from any electronics retailer, or ebay.
The circuit is:
At normal, the three resistors make up a voltage divider, so that the output from r3 can be adjusted as required.
When a train passes over r1, its resistance goes much higher, reducing the output.
This output can then be used for almost any other circuit via transistor, microprocessor, LED etc.
The values of r1 and r2 were 2k at normal (4.5k when dark), but nearly any approximate value will work because r3 is used to obtain whatever value you require.
R2 is essential as it acts as a compensator for varying light conditions around the layout, or for night time running. If the light level alters, both r1 and r2 will change at a similar rate. This keeps the voltage divider ratios about equal.
For DC users, the voltage onto R1 could be taken from the NORTH rail (positive), and ov from SOUTH rail. But output will always depend on the input voltage. So a train moving slowly will not provide 12v (more like 6v). Also, a train moving in reverse will provide a different output.
Clever stuff from Steve when it comes to detecting trains.
And now on to a subject I’m very keen on: making a start!
We finally made a start on the layout.
I love reading your post and your latest hall of fame inductees are well deserving, so congrats to the dynamic duo.
We decided to use RRinabox for the modules and then we have kit bashed it to redesign the extra track…our oldest son has gotten involved and he is way smarter than us. So it may get to suffisticated for Vicki and I to run.
There are 3 continuous loops that we can switch and run a train from outside upper loop all the way to inside lower loop and back out.
Its kind of cool and takes about 18 minutes with some operations of manually switching turnouts and crossovers.
The layout is currently 42″ x 96″ and we do have a plan to later add another module for the saw mill.
That’s all for now and we will send more pictures as we progress.
Your Texas fans,
Sid and Vicki”
Lastly, a question from John which I thought worth posting, as I’m sure it would help others in the interest of making a start:
“Alastair, I have been a member so to speak for several years and I have finally acquired a room for a layout.
For me when I say “just starting out” I mean it.
Haven’t built a layout for several years due to lack of space. DCC, which is what I want, is new to me and my question to you is: what do I start with?
I am working on a 8X10 HO layout to begin with. Engines, cars, track, switches etc.
Any help would be greatly appreciated. I have really appreciated your work on the blog and all of the additional comments made by so many people.
John “Red Label” Walker”
Please do leave a comment below if you can help.
A big thanks to Steve, Sid and Vicki.
All these years in and it’s still wonderful to see your solutions to specific problems.
And of course, it’s great to see those ‘starts’ because that’s where the magic is.
That’s all for the this time.
Please do keep ’em coming.
And if today is the day you get started on your layout, the Beginner’s Guide is here.