Toilet Timer to the Rescue

Introduction: Toilet Timer to the Rescue

The Story
Imagine working at the office from nine to five punching numbers in a computer the whole day...All you have to hold on to is your coffee break! Fortunatly, it is not that black and white for most people. We do have something in common though. There is a time that each and everyone of us needs to take a bathroom break. At some point, all the coffee we drink needs to leave the body, doesn't? So you are on your way to the comfort room as you where holding up every drip of coffee while finishing up that report. You're in a hurry because you 'need to go'... When you arive at the cr, you rush to open the door and you are about the enter 'the little zone'. But, what is that smell? My goodness, who burried there dead cat in here? That's really nasty!!!!

You get the picture right?
I had an artist sing a song about it for me. You can listen to it's attached.

If only there was a way for the previous visitor to leave a notice....
Well, There is now! This talking CR Timer. will indicate the level of 'danger' using some leds and on top of that, it plays funny sounds at each level. When the visitor is done doing his thing, one can press the button on the CR timer to give an indication of the 'danger' to however is visiting next. It's a timer, so it will count down. The level will automatically move doen a nutch, every three minutes until, after the lowest level of danger, it will shut down.


You Will need:

  • PCB --> Get it here <--
  • BC547 transistor
  • Arduino Nano
  • String of 5 pixelleds ( WS2812 or simular)
  • A speaker
  • And SD Memory card
  • Battery or power supply 9V

To make a nice frontplate with the drawing provided you'll need:

  • A color printer to print the image file
  • a laminator and a laminate sheet to laminate the image.
  • a tool to punch holes in the front for the led and switch
  • Some wires to connect all
  • Glue and tape
  • A soldering iron to solder the connections

Step 1: Schematic Explained

The arduino Nano works on 5V power. Instead of using the onboard converter, I decided to use my own. U1 will convert the input voltage to 5V ( VCC ). However there is more to is then that. When the unit is first connected to power, the regulator U1 will not get powered because Q1 is not conducting. To conduct it, one needs to press the button SW1. This will set a positive voltage on the gate of Q2 and as a result, Q2 will start conducting . This will put a negative voltage on Q1 so that Q1 will start conducting and the regulator U1 will get an inputvoltage.

As soon as the button SW1 is released, Q2 will stop conducting and as a result so will Q1. However, if SW1 is pressed long enough, the arduino will boot up and it will make D5 high. ( Override) The override is connected to Q3 that will start to conduct to take over the function of Q2. Now SW1 can be released and Q1 wil keep conducting.

To switch off the regulator( and everything connected to it) the software in the arduino has to make D5 low.

At this point, the software is programmed to make D5 low when the timer is done or when SW1 is pressed longer then 3 seconds. SW1 is also connected to pin D6 of the Arduino to monitor when it is pressed.

SD Card Interface
Because the SD card workd on 3.3V, the 5V VCC is converted to 3.3V with U3. U2 us used to do some level switching from TTL(5v) to 3.3V for the data and clock lines.

Arduino and other stuff
U5 and U4 don't need to be assembled. I just make it a habbit to "break them out" on the PCB in case i need them in the future.

The Ledstrip ( WS2812 5 leds) can be connected to P1 while a speaker can be connected to CN4. The sound isn't very load. You can use an amplifier if you like to increase the volume but you might have to use a filter because the output signal comming from the transistor is a PWM signal.

Step 2: PCB

You can buy an assembled PCB here:

Or you can make/order your own pcb, using the gerber files. If you like to assemble it yourself, you can take a look at the assembly drawing and the BOM list for the parts you'll need.

All the files you need are on my github:

Github Files

You can upload the gerber files to They offer great service for a good price!

Step 3: Connecting All Together

After you soldered the missing components onto the PCB board, you can start connecting the parts.

In the picture you can see where the speaker and switch are connected and where to connect the powersupply.

Make sure you hook it up correctly!

Step 4: Program the Arduino Nano

I used the Ardduino IDE to program the Arduino nano.

The sketch can be downloaded here:


Step 5: Prepare the SD Card

Format an SD Card as FAT32 and upload all the files with .wav extension.

Step 6: Make a Nice Frontplate

I Printed the front image on a color laser printed and I used a laminating machine to laminate the image. That way it has a glossy look and it will last longer.

I used a punch tool to make little holes where the leds will be mounted.

Step 7: Show and Tell

This is the result. I Used a 9V Battery as power supply.

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