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Overview The circuit uses a LED array to create a heart shape device that can be used as a gift during Valentine’s or any special occasion. Explanation The device contains 20 LEDs that are being controlled by 11 signal wires. The individual wires along the external side of the cardboard are functioning in pairs with the oppositely-connected LEDs. The LEDs are alternately illuminating constantly between high and low voltages. An LCD screen is added for displaying personalized messages. The device is using an interrupt timer and interrupt handler for handling the switching back and forth of the row driver. The single row driver is set by the interrupt handler in the forward and backward direction of the LEDs. A twinkling effect of the LEDs is also employed in this device by taking advantage of the LEDs’ duty cycle. This is done by increasing a counter that roll over to zero every 64 ticks every time the row driver switches back and forth. A brightness level between 0 and 64 is stored for each LED. The LED will be very dim if it is ON for one cycle but will be on maximum brightness for 64 cycles. Read More
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