RelayTimer

Relay Timer

Simple timer with a two button interface and LCD screen to show the time remaining. Intended to control a relay but could be used for anything else really.

Dependencies

I couldn't find it on the PlatformIO library explorer, but this project requires the LiquidCrystal_attiny library.

Features:

• Adjustable time, goes up to 9:59:59 max by default but can be adjusted
• Timer is pausable whenever needed
• Can easily reset the timer while paused or before starting

Wiring

Intended for an ATtiny85, this could definitely be ported to other microcontrollers if needed. Will need slight adjustment due to the direct port register manipulation though.

• NC = No connection
• FB = Function button
• TB = Toggle button
• SCL goes to SCL
• SDA goes to SDA
• Relay goes to a transistor (or straight to a relay if you're feeling bold (don't do that))

             ATtiny85
             __   __
 NC <- PB5 =|1 *-* 8|= VCC <- +5v
 FB <- PB3 =|2     7|= PB2 -> SCL
 TB <- PB4 =|3     6|= PB1 -> Relay
GND <- GND =|4_____5|= PB0 -> SDA

Hardware

• ATtiny85 or another microcontroller (will require modification)
• LCD with I²C support (I'm using a 1602 screen with a PCF8574 board)
• A relay module
• Two buttons
• A single NPN transistor (I'm using a 2N2222)
• A few resistors (2 4.7kOhm and 5 1kOhm)