This instructable is for a 30 Day Reminder Timer for Monthly tasks.

The purpose of this timer is to remind you when 30 days have passed and that you need to do your monthly tasks for your home and autos. The difference between this timer and just setting a reminder on your calendar is that it will continue to remind you even if you don't have time to do the tasks right away. You should put it in a place you walk by frequently such as your garage or basement. When you plug it into a power outlet and press the red reset button, the first green LED light will be lit. As the days pass, the LEDs will light up one by one across the box from green to blue to yellow. Once 30 days have passed the flashing LED in the middle of the box will begin to flash and continue to flash until you press the red reset button which starts the cycle again.

I got the idea for this from my brother who said he would like a device to remind him to change the filter in his heating and air unit. I had just started learning about electronics and thought this would be a good project to try. I did some research and found a lot of timer circuits for a short duration that used a 555 chip but not many long term timers. I did find a couple of similar longer term circuits and I chose this one as the base for my timer. I had to modify it by swapping out the relay for LEDs and calculate the resistor and capacitor to bump up the time from hours to 30 days. I also incorporated a battery backup circuit from this web site. This prevents a brief power outage from resetting your timer.

So, if you would like to put together a fun electronic project then continue reading.

The video illustrates what will happen over the 30 day cycle. To speed up the cycle I connected the top of the project case to my breadboard test circuit and used a small capacitor value. By doing this, you are able to see what will happen during the 30 days in just a minute and a half.

This instructable explains how I created my timer. You can take the circuit diagram and use your creativity to customize your own version.



  • Soldering iron
  • Drill
  • Drill bits 7/64, 9/64, 3/16, 1/2 inch
  • Multi-meter (only needed if you have problems)
  • Stopwatch timer

Here is the Circuit drawing in a PDF file.

Step 1: Prepare Circuit Board

The circuit board I chose for this project is laid out like a breadboard. It made it easier to transfer what I had set up on the breadboard to the circuit board. You will only need a small part of the board. Cut it down to 3 1/8 inches which should give you 29 to 30 rows of holes. The board is not a perfect fit for the mounting posts in the project case so only two screws are needed to secure it. Because the board was cut there is no mounting hole in the bottom right corner of the board. You will need to drill a 7/64 inch mounting hole. It is helpful to place the board in the case to measure where to drill the hole. Note: The project case doesn't include the screws to mount the board. I found two in my spare screws bin. I always save the screws from any device I disassemble.

Step 2: Solder Components on Circuit Board

Start by soldering the IC sockets on the board in the position noted in the picture. These sockets are not required but I prefer to use them to keep the heat of soldering away from the chips. It allows for easy chip replacement if one goes bad. The two 8 pin sockets will not have chips inserted. I use them for wire connectors to avoid having to solder the power wires to the circuit board. I decided to try this so I could remove the circuit board from the case without having to de-solder the wires if any component needed to be replaced. The second 8 pin socket is only used for testing. It makes it easy to insert a test LED and then remove it after testing. If you choose to not use these sockets, simply solder the components and wires to the cicuit board.

Next, solder the jumper wires to the circuit board as shown in the picture. I used different color wires to help me remember how they are being used.

  • Green is for ground (negative)
  • Red is for power (positive)
  • Blue is for the timing components
  • Orange connects the two IC Chips together
  • Yellow is for the reset circuit

Solder on C2 (1uF), R1 (1M), R5 (1M), D1 (1N4007), D2 (1N4007), D3 (1N4007), and POT1 (500k or more)

TIP: When soldering components you can use a rubber band to hold them close to the circuit board since it will be upside down while soldering. Bending the pins also helps.

Note: Make sure you place the diodes in the same direction as shown in the picture. Look for the silver band on the end.

Solder on the 7805 regulator, R2 (8.2M), R3 (220ohm), R4 (220ohm), and C1 (100uF) capacitor. Make sure you place the C1 capacitor correctly. The white stripe goes to ground.

Insert the IC 4060 chip in the left socket and the IC 4017 chip in the right socket. Both chips should have the indention on the left.

At this point the circuit board is complete except for the LEDs and the reset switch.

Step 3: Modify Case

The case needs to be modified to include the power connector and holes for the LEDs and switch.

Drill a hole in the side of the case for the power adapter connector. For the connector I used, I drilled a 19/64 inch hole. If your connector is different adjust the drill size accordingly. If it is square, you'll need to file some corners in the hole.

Solder 2 solid 22 gauge wires about 4 inches long to the power connector. I used one red and one black. Put the power connector in the hole of the case and glue it to the case.

Layout the design you want for the LED lights and switch. I opted for a straight line but you can place them wherever you like. Ensure the switch is positioned so it doesn't hit the circuit board when the case lid is closed. I used blue painter's tape to cover the lid. This gave me something to mark on and it helps to keep the drill bit from wandering while starting the hole.

I used a 7/64 inch drill bit for the small (3mm) LEDs and a 3/16 inch drill bit for the large (5mm) LEDs. I didn't have a bit large enough for the switch hole so I drilled a 1/2 inch hole then used a small file to make it bigger.

After drilling, remove the blue tape.

Step 4: Prepare Case Lid

Insert the switch into the hole in the case lid and tighten the nut.

Solder about 1.5 inches of solid 22 gauge wire onto your 9V battery connector wires. I chose to match the red and black colors of the connector wires. Then use some heat shrink tubing to insulate the solder connections. You can use a heat gun or, as I did, rub the side of your soldering iron on the tubing to shrink it. Insert the 9V connector wires into the 9V battery compartment of the case and out into the main compartment. Put a small zip tie around both wires. This creates a strain relief for the wires so you won't pull the wires off the circuit board when changing batteries. Note: the battery is just for backup. The timer runs on the wall adapter power.

Now prepare the LEDs with wires. For all the LEDs, clip the legs down to between 1/4 and 1/8 inches. The each leg should be just long enough to solder a wire onto it. My LEDs had a flat spot press into the leg and I used it as a good place to cut them. For each of the green, yellow, and blue LEDs, solder on a red stranded 24 gauge wire to the positive leg. It will be the leg on the opposite side from the flat side of the LED. I used stranded wire instead of solid wire because stranded wire is more flexible. Since the LED wires will need to be folded down to close the case lid, I thought it would be best to use stranded wire. Cut a small piece of heat shrink tubing and place it over the solder joint and shrink it. For the flashing LED cut the legs short and solder both a red and green wire to it. The red wire goes on the positive leg and the green wire on the negative leg. Use shrink tubing on both joints. You should now have 10 LEDs that look like the above picture.

Insert the LEDs into the holes in the case lid. Arrange them so all the negative legs are aligned. Cut a solid 22 gauge wire about 2 1/2 inches and remove the insulation. Weave this wire over and under the negative legs of the LEDs and leave a little extra on the right hand side. Solder this wire to each LEDs negative leg. Cut about 4 inches of green stranded 24 gauge wire. Solder this wire to the right hand end of the LEDs negative wire.

Cut 2 wires for the switch. They should be about 3 inches of 22 or 24 gauge wire. I used red and yellow for the colors. Solder them onto the switch legs. It doesn't matter which is red and which is yellow.

Step 5: Connect LEDs to Circuit Board

Solder the positive red wires of the LEDs to the IC 4017 chip on the circuit board.

LED 1 to Pin 3, LED 2 to Pin 2, LED 3 to Pin 4, LED 4 to Pin 7, LED 5 to Pin 10, LED 6 to Pin 1, LED 7 to Pin 5, LED 8 to Pin 6, LED 9 to Pin 9, LED 10 to Pin 11 (LED 10 is the Flashing LED)

If this isn't clear, reference the pictures above or the circuit drawing to better see which LED goes to which pin on the chip.

Solder the LED's green negative wire to the circuit board. Solder the switch's red and yellow wires to the circuit board.

Step 6: Putting It All Together

Place the circuit board in the case and secure it with 2 screws.

Push the power connector's red and black wires into the left most holes of the first 8 pin IC socket.

Push the 9V battery wires, red and black, into the next two holes in the 8 pin IC socket.

I chose the 22 gauge solid wire for this because it provides a tight fit. If the wire will not insert into one of the holes, you can rub fine sand paper on the end of the wire until it fits.

Insert the legs of a test LED into the right most holes of the second 8 pin IC socket. Make sure the flat side of the LED (negative) is in the bottom hole. This LED will be used in the next step which is calibrating the timer.

Power up the circuit board by inserting the 12V AC adapter into the power connector of the case and then the other end into a wall outlet. Connect a fresh 9V battery to the 9V connector. At this point, the first green LED should be on. The red test LED may or may not be on.

Step 7: Calibration and Final Assembly

At this point the timer should run for about 30 days but it needs to be calibrated to be more accurate.

You will need some type of stopwatch timer to do the calibration. I used the stopwatch mode of the clock app on an iPad.

The red test LED should be turning on and off about every 2 and half minutes. Time the on and off cycles by starting the stopwatch when the LED turns on and press the lap button when it goes off. Keep pressing the lap button each time the LED goes on or off. Do this about 5 times. Your times for each lap should be around 2 and a half minutes. Because each individual time will vary due to inconsistencies in your reaction time to the LED, average these lap times to get a more accurate overall time. The ideal time is 2:28.89 but anything between 2:28.0 and 2:29.99 is fine.

If your time is less than the ideal time, you can turn the screw on the potentiometer clockwise. It might take several turns to change the time depending on your potentiometer. Repeat the timing of the test LED. If your time is greater than the ideal time then you can turn the screw on the potentiometer counterclockwise and retest. You can see in the picture that my timing is a little high but my potentiometer limit was reached and I didn't want to replace my resistor of capacitor to make it perfect. The tolerance on one of those components must have been off enough to cause this issue. The amount of time off from the ideal time will multiple over the 30 days. For my timer, that equates to about 4 hours over the 30 day cycle. I can live with that.

Once you're done adjusting the timing, you can remove the test LED and close the case with the four provided screws. You will need to bend the LED and switch wires to get the lid to close.

You have now created a 30 day Reminder Timer. Mount it somewhere you typically walk by each day so the flashing LED will get your attention. The pictures above show different ways you could position the unit.

Once 30 days have passed and you have completed your tasks, press the red reset button to start the cycle again. If you buy a three month air filter for your furnace, you can develop a system to mark the passing of each month so you will know when three months have passed. Maybe mount some pegs on the wall and move something to the next peg each month.

I hope you have enjoyed reading my instructable and that you are successful in making one.

<p>Great way to remember stuff. </p>

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