One of our customers was trying to build an accessory decoder using our I2C-RELAY16 to drive a bank of relays for high current loads, and they were having a bit of trouble. So, I thought I’d sit down and work through the issues tonight, as I’ve always thought having an accessory decoder with isolated, high current relay outputs might be nice.
Ever wanted to control some real world hardware with your Raspberry Pi? Every now and then, we get questions about using either our I2C-RELAY16 or I2C-XIO boards from the Pi, and it’s been on my eternal backlog list of “I should do a quick article on that…” So let’s break this logjam and get down to controlling a cheap Chinese 16 channel relay board with a Pi (available from SainSmart and others). Because this provides 16 relatively high current, isolated output channels, this seems a great place to start, and it’s an easy hour project.
A Raspberry Pi 3 controlling a 16-channel relay module on my bench
You may have heard about the Modular Signal System – it’s been slowly gaining support in the Free-mo modular community for about a decade now. If you haven’t, read on – it’s an exciting new (well, somewhat new) option to bring ABS signalling and more to your model railroad.
The initial Modular Signal System (MSS for short) proposal was put forth by Gregg Fuhriman in the February 2005 issue of RailModel Journal. He’d developed the idea along with others to bring simple signalling capabilites to Free-mo modular meets. Traditional solutions, using pieces such as C/MRI or Loconet-based systems, are impossibly cumbersome to deal with in an infinitely-reconfigurable modular setup with participants coming from all over. What was needed was an acceptably realistic signalling system that was plug-and-play – no reconfiguration required for the myriad of ways their modules could be put together at each meet.
While I’m still a firm supporter of the tried-and-true industrial foam tape method we’ve sold for MRServo servo switch machine mounting since the beginning, there’s always room for improvement. Several customers have asked about alternate, mechanical mounting methods, and there’s definitely places that would be useful. I always have a machine or two that keeps getting knocked loose as I accidentally catch the wire with a tool, or sometimes a spot on the plywood that just refuses to adhere well.
The “conventional” solution would be to have injection molds made, and then have a run of several hundred or thousand parts produced. This is obviously expensive for us, highly speculative that somebody will actually buy them, and beyond what the meager profit margins on servo switch machines justify. Fortunately, we live in an absolutely amazing time in terms of manufacturing processes, and nothing is more exciting right now for manufacturing complex plastic parts than 3D printing.
The 3D model of the MRServo-2/-3 Bracket
Michael and I will both be out on other business next week, so orders placed between March 19 and March 26 will be delayed until we return the following week. We apologize for any inconvenience, and wanted to let you know in advance.
I’d like to introduce you to ISE’s latest model railroad product – the CKT-BD1 single channel DCC block detector!
The CKT-BD1 – our brand new single channel DCC block detector
This little DCC current-based detector is designed to be highly sensitive while being resistant to false triggering, robust, and very easy to install. All you need to do is pass one of the bus wires to the block to be detected through the current transformer and provide 5-18VDC to power up the detector. It can run on as little as 5VDC at 15mA, so it’s perfect for connecting to digital logic such as Arduinos or C/MRI systems. It has open drain outputs for both detecting and not detecting states, so it’s compatible with a wide range of other model railroad products such as the Modular Signaling System, C/MRI, input modules for systems like JMRI, standalone signal sytems, or even just seeing if there’s something in that hidden section of track on your layout. It also has adjustable sensitivity, so you can tune it to ignore leakage current through your trackwork while still picking up minute currents from rolling stock. Precision current measurement circuitry and a little digital microcontroller onboard helps filter the response so that you achieve maximum sensitivity without false triggers.
The development of ISE’s block detectors has been a fairly long adventure, so much so that the long, drawn-out development cycle through six or seven iterations has become a bit of a running joke between Michael and myself. It’s served as a bit of a high water mark in terms of design revisions and major overhauls, and every time Michael and I have to rev something, there’s usually a comment of, “well, at least it’s not the !@#$ block detectors again…”
With today’s introduction of the CKT-BD1, I thought it might be interesting to let you all in on how this evolved, and how we arrived where we are today – a rock solid design that I believe in as much as our bulletproof IR sensors. It’s the sort of thing that no sane manufacturer would do – sort of like running the corporate dirty laundry up the flagpole and waving it around. But then again, we’re a different sort of electronics company, and Michael’s been arguing for years that I’m not quite sane…
Michael and I will both be traveling to spend the holidays with our families, so shipping may be slightly delayed. We wish all of you a merry Christmas with your families as well!
Time Locks – An Introduction
In the real world, manual switches within signalled territory are protected by devices called “time locks”. The purpose of these is to prevent a switch from being opened in the face of an approaching train. When the conductor wants to open the switch, he unlocks it and starts the timer running (how this is done depends on the model of time lock). The time delay gives any train too close to stop – or sometimes too close to even see a restricting signal – time to safely pass over the switch before the points are changed. It also triggers the signal system to display restricting aspects around the block, so trains that are further out are alerted to the presence of an open switch.
Once a programmed amount of time has passed, the timer indicates to the user that it has expired (often by a white or green light) and then releases a locking mechanism that allows the points to be moved manually. (This is commonly done with a locking pin through the throwbar that is retracted, but there are other mechanisms.)
Time locks aren’t just a good idea – they’re required by law here in the US. Under 49 CFR 236.207, either approach or time locking is required of manual switches in signalled territory.
The idea of a clock that runs faster than real time to compensate for the compression in our model world is nothing new. The idea has been with us since at least the 1960s. It provides a way to schedule our operating sessions, providing a sense of real time passage and urgency without needing literally thousands of feet of track to represent the vast distances covered by our prototype railroads. Aside from being a display on the wall, guiding operators’ train movements, fast clocks have remained an isolated system, our model world unaffected by the passage of scale time. Think about all the things in our daily lives that are linked to the time of day and you’ll quickly realize how odd that is given all our other technological advancements, and how much potential is in that idea. I believe fast clock integration is one of the huge, unexplored areas left in the hobby today for added realism.
In this article, we’ll show you how to build an inexpensive device that allows you to synchronize items on your layout to fast clocks by using MRBus, the networking protocol that connects the Iowa Scaled Engineering Networked Fast Clocks, in conjunction with the popular Arduino prototyping environment.