Mobile Charger Timer Using Attiny85

• ATTiny85
• 100 Ohms (3 nos)
• 1K Ohms
• 10K Ohms
• 1N4007 diode
• NPN Transistor 2222
• 5V Relay
• 3mm Green LED (4 nos)
• Push button ( momentary)
• Universal PCB
• Cheap mobile charger
• Wires
• Old power adapter case
• 220V 2 pin female socket
• Soldering Iron
• Hot Glue Gun

• Charlieplexing is a technique for driving a multiplexed display in which relatively few I/O pins on a microcontroller are used e.g. to drive an array of LEDs. The method uses the tri-state logic capabilities of microcontrollers in order to gain efficiency over traditional multiplexing
• ATTINY85 has 5 I/O pins
  • 1 for Button
  • 1 for Output to control Relay
  • We are left with just 3 pins for LED
  • I needed atleast 4 leds
• Using 3 pins, one can get upto 6 LEDs, for this instructable, I will use only 4
• Please watch this youtube for more details

• Using All 5 Pins from ATTINY85
• Please note the physical pin number on ATTINY85 is not same as the logical pins, See the pinout diagram attached
• Note 220V wire are marked in RED

• I used Ardiuno Nano for prototyping, this helped me to test my code and fix any bugs
• Also it is easy to write code on nano and test all functionality
• Once all the bugs were fixed, Burn the code on a ATTINY85 using Ardiuno Nano as ISP
• Steps to make a attiny85 programmer
• Tested the circuit with the relay to avoid any issues later
• Code on my Gdrive
  • To test the everything is good, set the time as 10Secs
  • When everything works as expected, set the variable to 3600 secs
• In Addition, you will need to add library to code attiny85 (http://highlowtech.org/?p=1695)
  • Set https://raw.githubusercontent.com/damellis/attiny... in Ardiuno IDE preferences
  • Install ATTINY library
• Set internal frequency to 1MHz

• For the outer case/box, I have used a old adapter (not working)
• Why ?
  • 3 pins molded
  • Enough space inside for all electronic
• Based on the 2 pin socket, cut a slot in the case and hot-glue it as shown
• Hot glue was applied on one side only (we donot want to seal the case for easy repair and code updates)

• The 4 LEDs and a button has to come on the front side of the case
• First solder the 4 LEDs in Charlieplex config on a PCB
• Based on the distance between each led, drill 4 holes on the case using soldering iron
• Then Hot-glue the 4 LEDs
• Drill hole for the button and hot-glue it in place with it's pins exposed

• Connect the ATTINY85 pins to LEDs, Transistor and the relay with resistors and diode as in the circuit diagram
• Do not connect the 220V wires yet
• To power our circuit, I am using a old cheap mobile charger, which is extremely tiny, this helps to putt everything inside the case
• Make sure all the DC connections are done and we can fit all inside the case
• Use multi-meter to check all connections are good and as expected, with no shorts etc

• 220V circuit
  • Connect both wires to input of 5V adapter
  • Connect one blue wire from AC is connected to output socket, directly
  • Connect the red wire to Relay Common
  • Connect another red wire from Relay NC to the output socket

• Before the case is closed, test everything
• Change the variable to 3600 sec
• Close the case and start using

I hope, you liked the instructable and do share your comments and suggestions