Step 1: Design
1. Well, this is LOG so I naturally decided to use an Arduino.
2. It would be battery powered since it will go in my bathroom.
3. I wanted it to show the day of the week and whether or not it’s shower day.
4. I also wanted to be able to toggle the shower day on or off if I wanted to change it.
The ‘standard’ Arduino, like the UNO is not very well designed for battery operation, so I decided to build my own Arduino on a PCB.
I decided on the Lithium 18650 battery as it’s my current favorite battery of choice. (see picture) This battery voltage will vary from about 4.2Vdc fully charged down to about 2.0Vdc.
Technobabble: One of the brains of the Arduino is the AtMega328P. Another current favorite for me. Now this microprocessor will theoretically operate with a voltage of 4.2Vdc down to about 1.8Vdc but I think in the Arduino standard environment it is limited to 2.9Vdc? Anyway, that’s good enough for me. However, at lower voltages, the clock needs to be reduced to 8MHz.
Eagle files are atttached, schematic and PCB. This schematic is my prototype design so includes parts I thought might be necessary. I did not stuff the DS1307, 32.768KHz crystal and battery holder.
I made and stuffed the PCB.
I installed different colored LEDs for the day of the week so it’s a little easier to distinguish one day from another. (My eyesight isn’t the greatest)
1 18650 Battery
1 18650 Battery holder
1 Shower Monitor PCB (Can be made with Eagle Cadsoft files)
1 ATmega328P microprocessor
1 28 pin IC socket
6 Male header pins
1 Tactile SPST switch
1 Tactile DPST switch
1 Capacitor 0.1uFd
2 Capacitor 22pFd
1 Cylindrical crystal 8MHz
8 LED 3MM (assorted colors)
1 Resistor 10K
8 Resistor 1.5K
1 JST2.0 connector set (male/female)