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Introduction

One vital ingredient of proper signalaing and decent computer control is the ability to know where trains are. For this purpose track is split into a number of blocks. As trains draw current from the tracks to move it is possible to use electronics to build a sensor for each block which will tell us when there is a train in the block.

The TOTI

The picture shows a completed TOTI from MERG, all the connectors to this module are through the 9 pins on the side. It needs to be supplied with power and connects two pins together (like a switch) when it detects current flowing. MERG kits (like this one) are only available to members so if you would like to use this method you will need to join.

Using the TOTI

The TOTI shown is simple to connect up, of the 9 pins down the side 1 is not connected, 3 are used to power the TOTI (+5V, -5V and 0V), 2 are connected to an opto-isolator on the TOTI, 2 are connected to one side of the track and one connect to one side of the controller. As always with MERG kits the instructions make this crystal clear.

For Computer Control

I'm going to be building a PCB to accommodate 8 of these TOTI modules and provide me with a very simple 10 pin output connector, this will provide each TOTI with the required power and connection to the track power supply. Beside each TOTI will be a terminal block to which the track will be connected. The switches in the TOTI will connect its pin on the 10 way connector to 0V.

For DC Control

I'm going to be building a PCB for each section of track which will connect the TOTI (and track) to whichever controller is selected for that section and will allow an I'm going to be building a LED on the control panel to light if the section is occupied.