Peter Schmid's Pocket Power Pack Lets You Run Model Railroads Wherever You Go
Forth-powered project, runnning on a Firefly BLE STM32 board, delivers battery power and locomotive control in one package.
Maker Peter Schmid has designed a "pocket power pack" that lets you take your model railroad projects wherever you travel — by combining a battery pack, throttle, command station, and booster in one compact box.
"Model railroading on the go. A battery operated power pack gives you the opportunity to take your model railroad with you," Schmid writes of the project. "No mess with outlets and cables. Build your Pocket Power Pack, get some sectional track, a locomotive (DCC or DC) and a few cars and you are in business. From the DCC point of view the Pocket Power Pack combines Throttle, Command Station, and Booster in the same hand held unit. No power supply is required as long as the battery lasts. You can recharge the battery with a standard smart phone charger."
The power side of the gadget delivers up to 0.5A of current with an adjustable rail voltage of 5–20V, driven by a 1,000mAh lithium-polymer battery — good, Schmid says, for running small HOe or N-scale locomotives for up to five hours, small HO locomotives for around two and a half hours, and medium HO locomotives for an hour, with a two-hour charging time from a 500mA micro-USB charger.
Aside from the battery the case houses a Firefly BLE development board, built around STMicroelectronics' STM32WB855 microcontroller, a USB charging circuit, DC-DC converter, current sensor, motor driver, and a user interface based around an SSD1306-based 128×64 monochrome display, eight push-button switches, a potentiometer, and a physical power switch. Interestingly, the firmware is implemented not in MicroPython or C/C++, as you might expect, but in Forth via a port of Mecrisp Forth to the STM32.
In DC mode, the controller can delivery 250Hz, 500Hz, 1kHz, 2kHz, 4kHz, 8kHz, and 16kHz output frequencies via pulse-width modulation with fast or slow decade modes for braking, while in DCC mode is offers four locomotive slots with a 0–126 speed, direction control, light, bell, airhorn, and mute options, and eight programmable functions, and can send DCC-EX commands over serial. The Firefly BLE's radio isn't wasted, either, with the controller offering the option to use a smartphone or tablet as an additional throttle.
The project is documented in full on Hackaday.io, with hardware design files and source code available under the reciprocal Creative Commons Attribution-ShareAlike license.