signal is fed through a 10K resistor which ensures a current limiting, as the protection diodes inside the microcontroller limit the input range between about -0.6V to VCC+0.6V. R4 and R5 form a divider which provides about 0.1V for the comparator reference. This is because the input threshold of a pin is about 2V (half of VCC) and the transformer outputs about 9Vac so the error for detecting the zero cross is high. synchronization I’m going to use the internal comparator. The “brain” is the Attiny13 microcontroller which should be enough for this simple task.įor the A.C. It is now time to put together the little schematic that does it all. output from the clock’s transformer I decided to take it from there instead of connecting somehow directly to the mains, although this means being a little offset. In order to dim the light, I needed synchronization with the A.C. Adding my circuit to the regulator’s load shouldn’t be a problem as it provides power for the clock’s display which is rather high compared to how much the ATTiny13 will consume. This provides 4.2V which is excellent for my circuit. Guessing that the clock’s controller would be in the similar range, I looked for another regulator on the board and quickly found another zenner diode + transistor pair (8). This requires 2.7 to 5V to operate correctly. As the function is not that complex, I decided to go for an ATTiny13 microcontroller which I already had. The next step was to find a way to power my circuit which will take care of the sunrise simulator. This is why it needed low pass filtering, to extract a steady dc which would turn on the regulator for the audio amplifier and radio. At first, I thought that there was no need for one, until I looked at what signal the microcontroller was providing: it was the beep-beep-beep signal which is used alternatively as an alarm (instead of the radio). An electrolytic capacitor and some resistors were placed there and this seemed like a filter. This is because the radio is turned on by any of the three signals, two from the microcontroller which are the alarm (7) and sleep function and one from the switch. Looking carefully I realized that it was controlled by another transistor and this by another one (3) which is turned on by signals coming from three diodes (4), (5) and (6): there is an OR function implemented there. The positive led me to a transistor and a Zenner diode – there was a simple voltage stabilizer for it (2). As this is one of the components that need to be turned on I followed the power supply traces. Looking at the components, the audio amplifier was a very known part, the TDA2822 (1). The first task was to open the alarm clock and find the alarm signal. Added some cable and plug and I had all I needed. A 150W halogen reflector seemed right for the job, especially because it was very low price. Next, off to the hardware store to buy a light source. These clocks are available in many models, some rather cheap, so I picked one up. I decided to make it as simple as possible for the beginning, so getting a normal radio-alarm-clock and modifying it seemed like a great idea. It seems like a more pleasant way of waking up, especially in the winter, so it had to be tried. Recently I found out about the idea of simulating the sunrise. Throughout my life I have used different ways of waking up: the usual alarm clock connected to a high power siren and flashing lights, a high power buzzer fed by AA batteries hooked to a portable alarm clock(for when traveling), and of course the most used is the mobile phone alarm.Īll these methods have worked, but they provide a rather sudden wake up. Waking up in the morning is a daily and early task. I am in no way responsible for any consequences which result from any use of information on this page. DO NOT attempt to build it unless you perfectly understand what you are doing. Warning: this circuit deals with mains voltage which is lethal.
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