Nixie Tube IoT Clock
Karl Fischer.
0
replies
Overview
This internet alarm clock takes some old war tech and mixes it with new age hardware to create an interesting time piece for any home.A GPS unit sources the latitude and longitude of the clocks location which is used to accurately check the current weather conditions of its location and display constant updates using pictures to an LCD. Using an internet connection and some custom PCB's, the current time for your local area will display on Nixie Tubes.
What are Nixie Tubes?
A glass tube contains a wire mesh anode, cathodes shaped like numerals, and a neon gas at a low pressure, in this case they provide an numerical display using glow discharge. The Anode is supplied with high voltage (170V) with series ballast resistor and one of the cathodes are grounded to glow for a value from 0-9 or dot.
Each tube needs 170-200V on anode, and one grounded cathode, The Tubes can be multiplexed which reduces area and cost dramatically. Only one cathode bus is needed, no need for individual cathode buses for each tub so each tube has individually controllable anode switches, but share common cathodes. This is achieved through multiplexing.
Multiplex procedure
Only the anode of the first tube is turned on, and the cathode corresponding to the first number is turned on. Second tube anode is then turned on, then the cathode with the second number is turned on, and so on. This process is cycled for all tubes repeatedly at a fast rate
The PCB board designed for this project were creating using KiCAD, a free and open source PCB design software. The necessary files to download and review the PCB schematics are attached bellow.
PCB
Demo Video
/media/uploads/fischk08/20161215_161535_001.mp4
Components
Mbed Microcontroller
Nixie Tube Motherboard Custom PCB
Details
- Drives tube holders
- Exposes shift registers to the host uC
- Shift registers drive cathode HV transistors
- Also controls anode and LEDs for each tube holder
- Fabbed by MakerStudio.cc
Wiring
| mbed1 | Nixie Mother Board |
|---|---|
| p24 | sdi |
| p23 | scl |
| p22 | rcl |
| p1 | cen |
| 3.3 | Vcc |
| gnd | Vcc |
- Mother Board must also be given 12 V
4x Nixie Holder Custom PCB
Details
- Provide socket for Nixie Tube for toolless replacement
- HV driver for anode (optocoupler)
- LED illumination
- Cathodes are exposed with IDC block connector for multiplexing
- Custom PCB fabbed by OSH Park
Wiring
Nixie Mother Board -> Nixie Holder1->Nixie Holder_n Connected using Ribbon cables with multiple IDC block connectors.
IN-12B Nixie Tubes (4x)
Can be purchased from ebay in-12b Nixie Tubes
GPS Module Adafruit Ultimate GPS Breakout
https://www.adafruit.com/product/746
Wiring
| mbed | GPS |
|---|---|
| V5 | Vbat |
| p13 | TX |
| p14 | RX |
| gnd | gnd |
Ethernet
https://www.sparkfun.com/products/retired/8790
Wiring
| mbed | ethernet |
|---|---|
| TD+ | P1 |
| TD- | P2 |
| RD+ | P7 |
| RD- | P8 |
uLCD-144-G2
Wiring
| mbed | uLCD | |
|---|---|---|
| VU | 5V | |
| Gnd | Gnd | |
| TX | P28 | |
| RX | RX | P27 |
| Reset | P29 |
Speaker
https://www.sparkfun.com/products/11089
SparkFun Mono Audio Amp
https://www.sparkfun.com/products/11044
Wiring
| mbed | TPA2005D1 | Speaker |
|---|---|---|
| gnd | pwr - (gnd), in - | |
| Vout (3.3V) or 5V | pwr + | |
| p18 D/A | in + | |
| out + | + | |
| out - | - | |
| Any DigitalOut px(optional) | S (low for shutdown) |
Light Sensor CdS Photocell
https://www.adafruit.com/product/161
Wiring
| mbed1 | Photocell |
|---|---|
| p19 | 1 |
| gnd | gnd |
Bluetooth module HC05-Module
Wiring
| mbed1 | HC-05 |
|---|---|
| p9 | RX |
| p10 | TX |
| gnd | gnd |
| V5 | Vcc |
Discussion
Due to RAM and library compatibility limitations, one MBEDs using an older build revision was utilized. The mbed provides time and alarm clock functionality, and weather data from the internet. Bluetooth messages can be received by the mbed for debugging. The uLCD accompanying MBED displays the weather conditions based on queries to a yahoos weather API and displays an image associated to yahoos weather codes, the images are stored locally on the uLCD using an SD card. The functions used to control the Nixie tubes were built into a custom library. The library allows for setting each individual tube or setting all tubes at once, as well as a function that dims the brightness off all tubes by a set amount. Using the photocell and the dimming function allows for the tubes to decrease in brightness at night and increase when needed during the day. The figure below illustrates the concept discussed.
Import libraryNixieTube
Provides class structure for simple control of Nixie Tubes using custom PCB
Last commit 15 Dec 2016 by Karl Fischer
Import programFinal_Lab_v1
Final Project for 4180 Nixie Tube IoT Clock
Last commit 15 Dec 2016 by Karl Fischer
Further Development
Update Bluetooth compatibility to change how improve how the alarm is set on the clock. Implement redundancy measures for time such that if Ethernet is unavailable GPS time will provide the static time on the clock. It would be beneficial to reduce RAM usage by putting large libraries, such as the Ethernet libraries, in scope.
Contributors
Don Gi Min(Section A) Emilly Pitts (Section B) Karl Fischer (Section B)
References
Please log in to post comments.