Electronics Projects
Tools, some for Digital Modelrailroads

(latest page update: 22 December 2013)

Below a description of hardware tools I made for different purposes. Most of these tools are also described in the documentation of my software. This page gives an overview of the tools.

Active RS-232 breakout box

Breakout boxes are in common use as visual indication of RS-232 signalling. These devices use LEDs as indicators. The simplest boxes are passive: draw the current for the LEDs from the RS-232 port. This is no problem in most circumstances, but sometimes this gives a distortion of the data communications, for example in cases of high contact impedances.
The better boxes are active, use their own power supply and have amplifiers to obtain a high input impedance.

Most breakout boxes, passive or active, have only a simple indication of a positive or negative voltage. RS-232 defines the range between -3V and +3V as 'undefined'. With the threshold voltage of a LED of around 2V even simple breakout boxes come close to a proper indication, and with active boxes this may be implemented with a couple of resistors.

Most breakout boxes are generally used 'stand alone' work and have no 'output' connector to feed the signal to a more sophisticated measuring device, such as my AsynMon program.

I have designed a breakout box which combines all advantages

A picture of the exterior of the breakout box shows the 3 level indications: green=low-voltage, red=high-voltage and both LEDs off means not connected (open). See also the schematics, a possible stripboard layout and a picture of the interior of this active breakout box.

2-to-1 adapter

When monitoring a datastream with a PC, for example with my AsynMon program, normally 2 COM-ports will be needed to capture both the transmit and receive datastreams. However not many PC's have 2 free COM-ports, certainly not Laptops. When the datastream is half duplex, that is when only transmit or receive is active at a time, then it is possible to combine capturing both datastreams and still be able to distinguish between transmitted and received data. It requires only a relatively simple piece of hardware, which I called a two-2-one (2-to-1) adapter. View its Schematics or picture, as well as a possible layout on a piece of strip board.
For a detailed description of its use in combination with my AsynMon program, see the docs with AsynMon.

S88LPT adapter

Reading of Märklin feedback encoders (S88) via the Märklin Interface is relatively slow and gives interference with sending loc and turnout commands via the same Interface. Using 'direct drive' (generating the digital datastream in the PC and sending it via a COM-port to a booster) is nice, but it lacks the possibility of reading feedback.

These are 2 reasons to provide an alternative way to read S88s. The possibility presented here is via the parallel (LPT) port of a PC.
This requires a small adapter to provide the necessary power and galvanically isolate the PC and modelrailroad to protect the relatively sensitive parallel-port of your PC. Herewith the schematics of 2 S88 adapters. The simple one uses only a buffer chip, the other is an opto-isolated variant of the first. See here a possible layout of the opto-isolated variant on a piece of strip-board, and the picture of a completely built adapter of the opto-isolated variant.

GamePort Information and Programming

Accessing the gameport is not very difficult, finding out how is somewhat bothersome. Herewith some links to general PC information, and mouse and joystick library for C-language programs. The most comprehensive package of information and software for game software development I found at the site of Gary Neal jr (click on 'Downloads' for the source material).
A scan of the pages of the original IBM technical reference manual for the game port is also available.

Electronics projects with PICmicro aspects

Download Description

Quadrature encoder circuits for rotary encoders version 1.0.4. To be able to use cheap mechanical rotary encoders, some additional electronics is required. A document contains the description of several circuits, in particular 1 equiped with a PICmicros to control 4 rotary encoders. See here the schematics.
The software (hex files for PICmicros) and a PCB layout file are in a separate package.
The circuits are especially designed to connect rotary encoders to FSbus for Flight Simulator.

PICmicro programming of LocoBuffer and LocoIO, version 0.8 LocoBuffer and LocoIO are PICmicro based devices designed by by John Jabour. Both devices are equiped with a PIC16F873.
Jisp is a JAVA application with which LocoBuffer devices can be programmed via a serial port, and LocoIO devices via a parallel port, without any additional hardware (such as a PICmicro programmer). It provides a Graphical User Interface, but is somewhat slow.
Requires Java 1.1.8 or higher with Swing and JavaComm.
For details of LocoBuffer and LocoIO see the Files section of the Loconet Hackers mailing list.
The source material is available.
Java, Freeware, released 15 October 2002.