Pressing the INCREMENT or DECREMENT buttons will increase or decrease the value the cursor is on respectively. The right angle bracket character is the cursor. SETUP - This brings up the SETUP screens. While the backlight is on, the buttons will perform the following tasks: The backlight will automatically switch on when the room is light. If no buttons are pressed while the backlight is on, it will switch itself off after 10 seconds when in a dark room. When the backlight is off, pressing any button will switch the backlight on. The clock has three buttons - SETUP, INCREMENT, DECREMENT and a TILT switch. Set time, current date, birth date and alarm.This is called hysteresis and depending on the amount of feedback, this moves the ON threshold higher and the OFF threshold lower, To solve this issue, a small amount of the output is fed back to the input as to enhance the change (positive feedback). That is the ON threshold and OFF threshold is the same. When the light level is close to the threshold, the comparator circuit will switch on and off when there is a small amount of light change. I used a simple comparator circuit with a trimmer potentiometer to set the light level to where he backlight should be permanently on. You can still switch it on for 10 seconds by pressing any of the buttons. When sufficient light is present, it will have a low resistance and the backlight switches on allowing the screen to be read, In a dark room, the resistance is high and it will allow the backlight to switch off. An LDR changes its resistance depending on whether it is dark or light. To solve the above issue, I added a Light Dependent Resistor (LDR) with a comparator circuit. The former wasn't suitable because I don't want my room lit up when I go to sleep at night and the later meant having to physically stop what I am doing to press one of the buttons to see the time. To turn on the backlight, you either had to compile the code to have it permanently on or physically press one of the buttons. The main issue I had with the previous version was that you couldn't read the display unless the backlight was on. This project is an updated version of my previous build.
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