I considered adding panel mount buttons, but decided to try a plunger type arrangement to extend the reach of the buttons to the back of the enclosure. The time setting buttons are surface mount buttons on the board. It’s not too exciting, measurements were taken for the display windows, mounting and mounting for the board. I decided to create a 3D printed case for the clock. Everything worked as expected with 1 display, so the remaining displayed were soldered in place. 1 display was solder and ready for testing. Once completed the 3.3V regular and final power related parts were installed. A large number of mosfets, diodes and resistors must be soldered. The hour/minute set button pull-down resistors were also installed at this time, without these, erratic setting operations occur.įinally it was time to complete assembly. The program was also modified to turn the display segments all on and off and the outputs of the I/O expanded were checked to verify it was sending the pulses expected to do this.
#FLIPCLOCK INCLUDE HEADINGS SERIAL#
Next the clock program was loaded and modified to print the time via the serial connection for testing. Resistor R4 was left unconnected so the charging circuit shorted. At this point I haven’t ordered the battery yet, so the battery connections were shorted (datasheet says to connect battery input to ground when battery isn’t used). Next the DS3231 real time clock and I/O expanded were added. With the parts in place and the enable pulled high, 12V was applied and 18.8V appeared at the output, confirming operation. There is also a very small 0201 capacitor. The resistors in this part of the circuit are small 0402 parts and are not labeled, so care must be taken to not mix them. The TPS61175 has a thermal pad on the bottom – a small amount of solder was applied to the pad on the board and flux added, with solder paste on the pin’s pads, hot air was used to heat the board and chip to affix the solder pad and pins. With the microcotrller tested and working, I decided to build the 19V boost converter. Going forward it will be powered by the FTDI interface or the onboard 3.3V regulator.
Note the bootloader was programmed with a 5V Arduino UNO, this is ok since the mircocontroler can operate at this voltage. A simple program to blink an LED at the D13 output was used – D13 is connected to an LED on the board and available via on an ISP pin. With the bootloader in place, loading a program via the FTDI serial interface worked as expected. It was then used to “burn” the bootloader on to the microcontroller, turning it in to an Arduino.
An existing Arduino UNO was programed with the in circuit programmer sketch. With these parts in place, it was time to test the Arduino functionality. Some some additional traces under ceramic resonator had to be cut to avoid shorts. This includes the 328p microcontroller, 8MHz ceramic resonator, reset switch and pull up resistor, related capacitors, and headers for ISP and serial programming.
#FLIPCLOCK INCLUDE HEADINGS PRO#
Due to the large number of components, it was broken down in to sub-circuits that could be individually tested as it was assembled.įirst the components that make up the Arduino Pro Mini were soldered. The board was assembled using hot air and syringe solder paste. The boards were received within 1 week of ordering. He used a different PCB manufacture, but JLCPCB read the files without a problem. PCBs were ordered from JLCPCB using the gerber’s provided on Coyt’s web site. The 19V is provided by a TI TPS61175 boost converter. A MCP23017 I/O expander is used for the needed number of outputs, also driven by i2c. The time of day is retrieved form a DS3231 realtime clock chip via i2c. After that, programs can be loaded directly via a serial connection (FTDI 3.3V) using the Arduino software.
The Arduino boot loader was “burned” to the microcontroller (an Atemel 328p) to turn it in to an Arduino. The displays are driven by what is essentially an Arduino Pro Mini, which runs at 8MHz at 3.3V. The polarity determines the direction of the magnetism and therefor sets or clears the corresponding segment. To reduce complexity and parts, the displays are multiplexed, much as 7 segment LED displays often are. An H-bridge is used to place the coil across the 19V supply with the desired polarity to set or clear the segment. A 19V, 1ms pulse through the coil leaves it magnetized. The segments have a magnet which is attracted or repelled by a electromagnet’s polarity. Details of my version are below and files for the 3D printed enclosure and parts list are at the bottom of this page.Įach segment of the display is driven by an electromagnet. You can find a detailed circuit description, schematic, gerber files for the PCB and plans for a acrylic enclosure on his site. Info from the manufacturer can be found here. This is my build of Coyt Barringer’s flip display clock using Ferranti-Packard 1″ electromagnetical displays.
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