Sunrise Alarm Clock





Introduction: Sunrise Alarm Clock

About: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker, and all around Mad Genius

Many people find the beep of an alarm clock to be a very unpleasant way to wake up. One alternative is to use lights to wake you up. For instance, a "sunrise alarm clock" gradually increases the brightness of a light near your bed at the set time. This helps some people to wake up more gently. 

So in this project I am going to show you how to build a light alarm circuit from a outlet timer and a hand full of basic electrical components. 

Step 1: Materials

Here are the materials that you will need to make the circuit:

AC Light Timer
USB Cable
USB AC Adapter
1 Mohm Resistor
4 X 100 ohm Resistor
10 kohm Potentiometer (Variable Resistor)
1000 µF Capacitor
Printed Circuit Board
Jumper Wires
Extension Wire (optional)
Momentary Switch (optional)

You will also want to have the following tools at hand:
Soldering Iron and Solder
Wire Strippers
Wire Cutters
Non-Conductive Tape

Step 2: The Circuit

This circuit is essentially just a resistor/capacitor timer with a transistor amplifier. The capacitor is initially discharged. When the power is turned on, the capacitor begins to charge through the 1Mohm resistor. As this is happening, the output voltage of the capacitor slowly increases. This voltage signal is sent to the transistor which sets the transistor's output. This causes the LEDs to gradually increase in brightness over several minutes.

The potentiometer (variable resistor) is used to adjust the starting voltage of the capacitor. This effectively lets you set the initial brightness of the LEDs. Without it, the LEDs would be off for a long period of charging before the output would be high enough for LEDs to begin to emit light.

The values of the 1000 µF capacitor and the 1 Mohm resistor were arbitrarily chosen for convenience. Increasing either of these values will slow down the charging process and cause the LEDs to brighten more slowly. Decreasing either of these values will have the opposite effect.

The IRF510 MOSFET was chosen for the transistor because it requires very little input current and is capable of driving a large number of LEDs.

Optionally, you can connect a normally open momentary switch to the two terminals of the capacitor to act as a snooze button. Pressing the button will drain the capacitor and restart the charging cycle.

Step 3: Assemble the Circuit

Following the circuit diagram in the previous step, I prototyped the circuit on a breadboard. When testing the circuit, remember that you need to discharge the capacitor between each trial. The LEDs brighten as the capacitor charges. If it is already fully charged then they will stay at a constant brightness.

After testing the circuit to make sure that everything was functioning properly, I soldered the circuit together on a printed circuit board. I decided to add a few more LEDs to make it a little brighter. Then I trimmed the circuit board to fit. Depending on how you plan to mount the lights, you may wish to add additional wire so that you can reach areas that are further away from the outlet.

Step 4: Mount the Circuit

There are a lot of ways that you could mount the light. The simplest way is to just place it next to your bed on your night stand. This can work but it is less effective if you are facing the other direction. Another option is to mount it over your bed in something like a hanging lantern. If you want the light to be more directional, you can mount it in an adjustable lamp that can be pointed at your pillow. If all else fails you can put the lights directly into a pillow, such as "Bright Light Pillows." Do whatever works best to wake you up.

Step 5: Set Up the Timer

Plug the timer into the wall outlet. Plug the USB AC adapter into the timer. Then plug the USB cable into the adapter. Set the timer to turn on about 15 minutes before you want to wake up. When the timer goes off, it will activate the circuit. The LEDs will then gradually turn on and hopefully wake you up. 

Step 6: Finished Sunrise Alarm Clock

Now you have your own DIY sunrise alarm clock. When you are first trying it out, you may wish to have a regular alarm as a backup just in case the light doesn't wake you up reliably.

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115 Discussions

Would it be possible to open up a cheap alarm clock, and some how have it's alarm trigger the lights?

1 reply

You could do that put you would need to add a whole different circuit to control the dimming if you wanted it to gradually turn on. If you just wanted the lights to turn on all at once, it would be easier to just use an outlet timer with a regular lamp plugged in

Hi. If I would add, say 5 more LEDs, what value of resistor should I put in series with each led. I dont have any idea of the computation that I should do. Thank you for the response.

I was wondering if you could help me ‘translate’ your 5V ‘Sunrise Alarm Clock’ into a 12V setup?
My goal is to make an LED strip I have (with 45 LED’s 12V) ‘fade in’ in somewhere between 10-20 minutes, like yours.
This is what I have on hand, based on your list:

-IRF510 MOSFET (effect: 100V-5.6A-43W) - should be fine for 12V?
-1 Mohm Resistor (effect: 1 Mohm / 1W) - Would this go with a 12V supply?
-4 X 100 ohm Resistor - didn't get them since resistors are built into LED strip.
-10 kohm Potentiometer (Variable Resistor) - Would this go with a 12V supply?
-1000 µF Capacitor (effect: 1000uF / 10V) - I couldn’t find any capacitors with 12V, would this 10V work? If not, could I use it together with an extra capacitator I have, with 2200µF / 10V? (I’m guessing no, but I’d love to hear your suggestion).

I’ve read all the comments, looking for answers, and I’m impressed how helpful you’ve been to everyone, hope you wont mind answering a few more questions!
Thank you

2 replies

Alternatively, if you have two 2200uF / 10V capacitors, you can put them in series to act as one 1100 uF / 20V capacitor.

All of those parts should work fine. You just need to make one small change in the design for the capacitor. You don't want its voltage to get above 10V. The terminals of the capacitor are connected to the 1Mohm resistor and the center pin of the potentiometer. So its voltage will be the difference in the voltage between those points. The 1Mohm resistors will eventually let the positive lead of the capacitor reach the full voltage of the supply voltage. But the voltage of the center pin of the potentiometer depends on the setting. The potentiometer makes a voltage divider.

Its voltage can range anywhere from 0 to the supply voltage. In order to prevent the capacitor's voltage from going above 10V, you want to make sure that the center pin of the potentiometer never goes below 2V. You can do this by adding a fixed resistor (at least 2.2Kohm) between the bottom pin of the potentiometer and ground.

If you have any other questions let me know.


1 year ago

Will this setup work on an AC power supply (no AC adapter)? I am planning on wiring an AC plug where the LEDs are located with the objective of being able to plug in a bedside lamp that would otherwise be plugged into a wall socket. Common sense tells me no, but I thought I would ask.

2 replies

If you just want to have the lights turn on with the timer, you can plug the lamp directly into the timer and it will work. But if you want to have the lights fade in, then you will need an AC dimmer circuit. To be honest, I am not sure of the best way to make one of those.

Thanks for the quick reply. I've looked into them, they just seem a tad more complicated.

I was wondering if instead of using an AC light timer, is it possible to use the RTC library in Arduino to set the time for the alarm?

1 reply

I am using this for a college project to gain a qualification in C&I and complete my apprenticeship.

I was hoping you would be able to tell me a few things about the project for my PDS:

- The weight of it.

- Approximate product life span.

- Quality and Reliability.

Thank you.

3 replies

The circuit itself is really light. Most of the weight will be from whatever you mount it in. It should last for the life of the LED that you use. It is a simple system. So it is pretty reliable. There is not much to break or do wrong.

Thank you. Could you also tell me the make and kind of potentiometer you have used? After building I realised I used one that you have to adjust, which is wrong.

Any kind of potentiometer can work. It is just used to set the initial brightness when the light turns on. If you want you can replace it with a fixed resistor or just leave it off. It isn't critical.

Can you please share steps on how to do this on a breadboard? 8 year old really wants to do this as his school project, we are in the thick of it right now. Would be amazing to get materials list and steps.

1 reply

Step 3 has a picture of the circuit assembled on a bread board. The circuit board used is also in the same configuration as a bread board so all the components can be placed in the same location.

great project

can i place your project on my website.

i'm working on a website which is related to electrical projects.

i also mention your name, link and other info.

plz reply

1 reply

This project is posted under Creative Commons Attribution. So you can feel free to repost it as much as you want as long as you include the proper attribution.

Hi, what PCB plate type (number ) you use to build it ?