Locodoco/Loco Decoder

This Page is part of the Locodoco project. It currently only contains some vague notes about the planned version of the loco decoder.

List of (planned) features

Common on both Versions

SUSI interface Support
internal 3.3V logic levels (for RFM12b)
measurement of rail voltage (= option for DCC integration)
measurement of generator voltage (motor speed/load regulation)
connector for IR transceiver
seperate out/inletlets for each, motor-driver and logic power supply (GoldCaps)
4 GPIO Pins
Processor: One out of Atmega8, Atmega168 and friends (all pin compatible devices)

Big version

5V power regulator, 3A
3 servo connectors
>= 3A constant Motor current
Socket for add-ons (shields)
2 N-Fets for high loads, 4A each, seperate rectifier to GND
4 additioal GPIO Pins

Small version

1A Motor current
Maximum dimensions: 22x60x10mm

Two Versions

Larger locomotives provide a "massive" amount of space and require some more Amps to drive their engine(s). While the big version of the decoder includes many features, the small version is a rather minimalistic approach.

The hardware design of both versions however is designed to be as flexible as possible, letting the user choose the components to use from a variety of parts. The Processor for example may be an Atmega8, which is rather cheap, or the more expensive Variant Atmega328.

"Big" Version

Schematic for the big version

A (preliminary) schematic for the big decoder version is checked into the SVN repository. It's main features are:

Seperate (optional) rectifier for the (optional) power regulator
Options for 7805 (and similar) and LM2576 (and similar) regulators
Two Seperate connectors for Goldcap buffers with current limiting, one for each, VCC and 3.3V buffering
3.3V Power regulator & logic levels
2 Mosfet power outputs (6A each), alternatively 2x500mA Transistor outputs
2 Switching outputs, 1A each + 1x500mA Output (shared with 2nd Servo connector)
2 Servo Connectors (with 5V voltage levels)
SUSI Interface (with 5V voltage levels)
Connector for infrared transceiver
Support for the RFM12 and similar communication modules
4A max. Motor current, 3A max. power outlet
DCC support (at least in hardware... ;))
2-gear load regulation circuit (with 4x gain "switch")
Track voltage measurement

Load regulation

A common feature among digital model railroad systems is load regulation and measurement of the actual speed of the motor. When performing scripted actions like (de)coupling cars on a certain point of the layout, it is essential to know the actual speed of the loco. I've done some experimenting with different circuits and documented the results in a small video.