xJacksee/Retro_Bubble_LED_Watch3Retro wrist watch built with ATMega328PB uC and HP 5082-7415 obsolete LED 7-segment display
Retro Bubble LED Watch is an open-source printed circuit board by xJacksee, from the xJacksee/Retro_Bubble_LED_Watch repository on GitHub, published under the MIT licence. It is a 2-layer board of 30.5 × 22.5 mm with 24 parts on 44 nets, routed with 400 tracks and 55 vias.
It is built around the ATMEGA328PB-AU, DS1337S+T&R and KMS231GLFS, with the LFXTAL016178REEL among its other parts. Its parts include 11 resistors, 3 capacitors, 2 ICs, 2 connectors and 2 switches. It belongs with the retro computing and games and wearables boards and the AVR (ATmega, ATtiny) boards of this library.
Retro Bubble LED Watch is a project dedicated to infamous HP's bubble LED seven segment displays produced around 1970s. The goal of this project is to create fully functional retro watch from scratch (including code) based around modern components while the aforementioned display being the centerpiece.
Retro Bubble LED Watch is a project dedicated to infamus HP's bubble LED seven segment displays produced around 1970s. The goal of this project is to create fully functional retro watch from scratch (including code) based around modern components while the afordmentioned display being the centerpiece.
The circuit features ATMega328PB microcontroller fulfilling the role as the display multiplexer and I2C communicator with RTC module. For the RTC IC a popular DS1337 has been chosen due it's low standby power, wide supplay voltage range and low price point. Along with this IC comes an external precision quartz crystal designed for digital watches. Due to space limitations a standard 3V CR2032 lithium coin battery supplies power to the circuit. The capacity as well as the footprint of this power source is quite large and thus the rough estimated lifetime of single cell might be as long as 2,5 years while normal use.
The programme has been written in Arduino using only Wire library. To upload the code it is nessesary to install and add Mini-Core library to Arduino IDE. The fuse bits settings for ATmega328PB have to be left at factory default (including clock - internal 8MHz RC colock have been used) according to official Microchip datasheet.
Please refer to to ATmega328PB's datasheet section 28.8. "Temperature Measurement" or AVR122 application note. Every MCU requires individual calibration. In this project, a single point calibration method was used. The offset value can be tuned in source code by changing the value of "T_OFFSET" definition.
Due to space limitations, an alarm buzzer couldn't be fitted on the PCB. Solder pads J2 provide a connection to the PE0 pin of MCU that turns on periodacly during the alarm. External piezoelectric disc can be connected to these pads and fitted onto the internal surface of the lid. The buzzer must not consume more than 40mA otherwise MCU can be damaged.
The case is designed to be 3D printed using any material. Supports are nessesary.
The CR2032 battery has the capacity to power the circuit for over 2 years but the accurate battery life is dependant on frequency of turing on the display which can consume up to 35mA in peak. This loads the battery and the voltage drop can couse the uC to shutdown when battery is drained. While in sleep the circuit consumes, according to manufacturers' datasheets maximum of arund 5uA in worst case scenario.
Szymon Bartosik
| Qty | Value | Footprint | References |
|---|---|---|---|
| 8 | 330R | Resistor_SMD:R_0603_1608Metric | R1, R2, R3, R4, R5, R6, R7, R8 |
| 3 | 100n | Capacitor_SMD:C_0603_1608Metric | C1, C2, C3 |
| 3 | 10k | Resistor_SMD:R_0603_1608Metric | R9, R10, R11 |
| 2 | KMS231G | Button_Switch_SMD:SW_SPST_CK_KMS2xxG | SW1, SW2 |
| 1 | ATmega328PB-A | Package_QFP:TQFP-32_7x7mm_P0.8mm | U1 |
| 1 | DS1337S+ | footprints:SOIC127P600X175-8N | U2 |
| 1 | HP 5082-7415 | Package_DIP:DIP-14_W8.89mm_SMDSocket_LongPads | DS1 |
| 1 | ISP Programming Connector | Connector_PinHeader_1.27mm:PinHeader_2x03_P1.27mm_Vertical | J1 |
| 1 | LFXTAL016178Reel | footprints:LFXTAL016178Reel | XTAL1 |
| 1 | LOGO | LOGO | G*** |
| 1 | Pad Connector | footprints:Pad_Conn_2x1_2x1mm_2.54mm | J2 |
| 1 | Panasonic CR2032/BN | Battery:BatteryHolder_Keystone_1060_1x2032 | BT1 |
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It measures 30.5 × 22.5 mm and has 2 copper layers, 1.69 mm thick.
24 parts, built around the ATMEGA328PB-AU, DS1337S+T&R, KMS231GLFS and LFXTAL016178REEL. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
From the xJacksee/Retro_Bubble_LED_Watch repository on GitHub, at the commit this page was made from: the board is kicad/Retro_Bubble_LED_Watch/Retro_Bubble_LED_Watch.kicad_pcb and its schematic kicad/Retro_Bubble_LED_Watch/Retro_Bubble_LED_Watch.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).