/retroclock

A retro-looking clock based on nixie tubes and LED bubble displays

Primary LanguagePythonMIT LicenseMIT

Retroclock

License: MIT

This is the code I made for one on my personal projects, a clock based on nixie tubes and LED bubble displays:

I wanted to create a fancy clock with a retro look so I decided to investigate old display tecnologies. I like retro stuff and tinkering with electronic things so bought some stuff to test. I ended using old soviet ИН-12Б and INS-1 tubes, and HP/Agilent HPDL-1414 LED bubble displays.

I also decided to hand solder all circuit boards because I really like the look of them:

I share the code and the overall design just in case is useful to anyone.

Nixie tubes

The module is based on 6 ИН-12Б tubes that shows the time and 4 INS-1 tubes that indicates the seconds.

The high voltage needed for the nixies to work is produced by a high voltage 12-24v to 85-235v boost module (NCH6100HV) configured to 180v. The boost module is fed with 12v through a NC relay controlled by a digital signal from the pin 23 (BCM naming) that feeds a 2N2222 NPN transistor to be able to switch the state of the relay with 12v. This way, for the 180v to reach the anodes of the nixies, a explicit 5v signal needs to be generated (and maintained) by the software, so all nixies will be normally powered off to prevent wear and ghosting of the tubes.

The nixie cathodes are managed using 5V digital signals using a high voltage BCD-to-decimal nixie controller (К155ИД1). The BCD signals are controlled using a Raspberry Pi and a 16-Bit I/O Expander (MCP23017) controlled via i2c. Two MCP23017 control 6 К155ИД1 ICs (3 each, 3x4 bits BCD) that manages all 6 ИН-12Б tubes. These MCP23017 ICs also controls 4 MPSA42 0.5A/300V NPN transistors that manages the cathode of the little 4 INS-1 tubes. I am not using the decimal point present in ИН-12Б tubes.

For the ИН-12Б tubes, a 33KΩ current limitating resistor is placed on the anode and for the INS-1 the resistor value is 270KΩ. With this values, aproximetely 1.2mA will flow through the ИН-12Б tubes and 0,5mA through the INS-1 at their respective (aproximated) sustaining voltages of 140v and 55v. I think that maybe a 1.2mA can cause the ИН-12Б tubes to not be as bright as they should (maybe a 15K resistor will be better) but I think that the look fine and this way the tubes will last longer.

A lot of the information about how nixies work, have been obtained from this hackaday project.

Datasheets and links:

LED bubble displays

The module is based on 4 HPDL-1414 screens. This screen can show a total of 16 characters symultaneously, and can be configured to show: date information, network information, weather information (retrieved from OpenWeatherMap using PyOWM) or any text. Text can also be configured to be static or to roll over the screen. The DIP switch changes i2c address for the MCP23017.

All 4 HPDL-1414 modules are connected to a MCP23017 I/O expander. All share the same 7 bits bus for data transmission to the modules and the same 2 bit bus for digit selection. Digits are written on the displays by multiplexing the bus using the WR pin on each module that is wired to independent bits of the I/O expander. Also one of the free bits left on the I/O expander is used to power on all the modules using a 2N2222 NPN transistor. This way all modules can be switched off if needed. The MCP23017 I/O expander is also controlled by a raspberry Pi using I2c.

Datasheets and links:

Raspberry Pi and REST service

All the assembly is controlled by a Raspberry Pi using i2c. I went with the Raspberry Pi (original one) because of its low power consumption and because I had one hanging arround. As a Linux capable device, I can have any other service also deployed on the system.

The Raspberry is powered from an external 12v power supply (the same that powers the nixie high voltage booster) after stepping down the 12v to 5v using a cheap Ebay step down converter.

The system is controlled by a simple Flask HTTP server that serves a REST service. The initial configuration of the service is located in config.py and it is also a direct representation of the REST service. GET or POST requests to /api/v1/general /api/v1/hp or /api/v1/nixie expose the configuration.

The clock is by default idle (nothing is light up) and a request to /api/v1/tick will trigger both HP and nixie workers. This will cause both nixies and HP screens will light up during 1 minute before returning to idle. All this behaviour can be modified using the REST service or editing config.py.

All the service is written in python 3, so some dependencies need to be installed:

sudo apt-get install python3 python3-pip

In order to run the service, create a virtualenv and then install the dependencies:

cd <route of the project>
virtualenv -p /usr/bin/python3 venv
source venv/bin/activate
pip3 install -r requeriments.txt

To run it, you can just run:

./run_retroclock.sh

If you want to start the service on startup, supervisor can be a good option:

sudo apt-get install supervisor

Create a new service file:

nano /etc/supervisor/conf.d/retroclock.conf

An example can be:

[program:retroclock]
command=/home/pi/nixieclock/run_retroclock.sh

stdout_logfile=/var/log/supervisor/%(program_name)s.log
stdout_logfile_maxbytes=200MB
stderr_logfile=/var/log/supervisor/%(program_name)s.log
stderr_logfile_maxbytes=200MB
startsecs=5
stopwaitsecs=5
autorestart=true

Reload everything:

supervisorctl reread
supervisorctl restart retroclock

About

Copyright (c) 2020 Guillermo Climent, https://github.com/willyneutron

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.