Hello, I have an alarm clock that I would like to modify, but don't quite know where to start. I have traced the circuit out, and I have found the alarm lead that I can get a signal from when the alarm is triggered. What I would like to do is have this control an outlet that I can plug a 120v (60x3 watt) lamp into. I realize I could do this with a transistor / SSR, however I would like the Lamp to fade on from 0 to 100% brightness over about 30-45 minutes, and then trigger an another circuit for the actual alarm. It would be nice if the shut-off for the alarm and the lights were separated. Any ideas on where to start with this?
Having a seperate reset for the alarm and the light probably isn't that difficult, you'll need to make a latching circuit (some sort of Flip-Flop, probably) for each one at some point. As for contrioling a mains device, it will likely be a Diac or Triac circuit. When it comes to buying components, make sure that you get ones rated for the voltage (and remember that the peak voltage is 40% higher than the listed voltage), and are rated for the current that the lamps will draw.
I would say use a PIC but then I could not advise you any further. For the scenario you are describing, you would have to construct a positive feedback loop (Biology is good). Consider the following: Let us say once the alarm signal activates, a 555 IC timer, acting as a PWM supply, starts firing a set frequency into the TRIAC/DIAC (Use TRIAC for less cost, use DIAC if you value effeciency). The light now comes on at a certain percentage. Next to the light, you have a CDS photocell that various its resistance based on ambient light. The variable resistor is hooked up to the 555 IC timer which you can guess will not be changing the width of its pulses because of light now on the varible resistor. More ambient light is apparent to the variable resistor and the 555 IC timer's pulse width changes more. Now you have a positive feedback loop.
Thanks for the input. I think I will have the output from the alarm clock trigger two flip-flops, one for the alarm, the other for the lights. The light circuit will fade on over about 30 minutes using some sort of capacitor / transistor / triac setup, and the alarm will use a 555 timer to estimate when the light will reach full brightness which will set off some type of alarm, to turn off the alarm, I will just reset it's flip-flop... I think... Anyone see anything wrong with that?
