New featured project by Tom

content/featured-projects/binary-clock.md

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+---
+title: 'Binary Clock'
+weight: 54
+---
+
+{{% notice tip %}}
+GITHUB PROJECT: [github.com/taartspi/pi4j-binary-clock](https://github.com/taartspi/pi4j-binary-clock)
+{{% /notice %}}
+
+This project by Tom Aarts (published on May 15, 2024), is a binary clock created with LEDs on a breadboard. In the video below you see it incrementing to the next minute and hour.  What you see is the Hour Minute and Second displayed in BCD (Binary Coded Decimal):
+
+<video controls width="800">
+  <source src="/assets/featured-projects/binaryclock/binaryclock.mp4" />
+</video>
+
+
+Design document describing the LED  PCF8575 connections, and the Java implementation that drives the clock LEDs.
+Note: there are two PCF8575 IC used in this design.  This IC is used as it can provide the current flow to
+directly control the LED.   Alternative IC like the MCP23017 with less current capability would require a NPN
+transistor in the circuit.
+
+# Wiring
+
+The following documents the connections for a single LED
+
+![Single LED wiring](/assets/featured-projects/binaryclock/led_connections.png)
+
+## LED Anode/Cathode
+
+![Diode](/assets/featured-projects/binaryclock/diode.png)
+
+## LED assignment
+Chart of 20 LED showing color assignment.
+![LED colors](/assets/featured-projects/binaryclock/led_colors.png)
+
+## Overall LED connections
+Higher level example of the twenty LED connections. This shows half of the LEDs. the same connection pattern
+repeats.
+
+![LED connections](/assets/featured-projects/binaryclock/led_connections_within_BreadBoard.png)
+
+![LED connections across entire BreadBoard](/assets/featured-projects/binaryclock/led_connections_across_breadboard.png)
+
+
+# Parts
+
+## AITIAO  PCF8575  16 IO Expander
+Since there are 20 LEDs, two ICs are required. In my case these parts I purchased do not match their documentation.  My chip has solder bridges for all three address bits, A0 A1 A2.  Also their description of a solder bridge across VCC-VDD appears to be backwards.  I think as  cautionary tale, I soldered the ICs down and lost access to their VCC-VDD bridge and couldn’t experiment.   
+This companies chip functions correctly with the Chip VCC and LED anode voltage equal.
+
+## LEDs
+Cheapos.
+
+## Prototype board
+Half Size BreadBoard.  You can see in the chart ‘Overall LED Connections’ I cut paths on the planar so the LEDs
+could be placed close to each other.  You can buy larger BreadBoards from ElectroCookie, called snappable.
+On these boards each row, ie: A B C …  has three solder lands and each letters trace are not connected to the
+next letter, so no trace cutting and there is more area for components and soldering.
+
+![Alternate BreadBoard](/assets/featured-projects/binaryclock/alternate_breadboard.jpg)
+
+# PCF8575  Connection Assignment
+
+![PCF8575 pin assignment](/assets/featured-projects/binaryclock/pcf8575_pin_assignment.png)
+
+# Pi Connectins
+
+The PCF8575 ICs and the Diode anodes connect to the Pi 3.3v
+The PCF8575 ICs connect to the Pi Ground.
+The PCF8575 ICs connect to the Pi SDA and SCL (I2C).
+
+# Java Implementation
+
+The Java project uses Pi4J V2.6.0 and you can find the sources in this [GitHub repository](https://github.com/taartspi/pi4j-binary-clock)
+
+Developed using pi4j 2.6.0-SNAPSHOT.
+
+
+# Completed project
+
+{{< gallery >}}
+{{< figure link="/assets/featured-projects/binaryclock/pcf8575_breadboard.jpg" caption="PCF8575 BreadBoard" caption-position="center" caption-effect="fade" >}}
+{{< figure link="/assets/featured-projects/binaryclock/led_breadboard.jpg" caption="LED BreadBoard" caption-position="center" caption-effect="fade" >}}
+{{< figure link="/assets/featured-projects/binaryclock/interconnect_pcf8575.jpg" caption="PCF 8575 wired" caption-position="center" caption-effect="fade" >}}
+{{< figure link="/assets/featured-projects/binaryclock/interconnect.jpg" caption="Interconnect" caption-position="center" caption-effect="fade" >}}
+{{< figure link="/assets/featured-projects/binaryclock/led_breadboard_operational.jpg" caption="Operational" caption-position="center" caption-effect="fade" >}}
+{{< /gallery >}}
+{{< load-photoswipe >}}
+
+# Alternate IC
+
+You could use a MCP23008 or MCP23017 as the IC. There are a few more steps to configure the IC, and its limited current capability requires a NPN transistor to switch the LED current.
+
+![NPN Transistor for MCP230XX](/assets/featured-projects/binaryclock/npn_transistor.png)
+