Capello wood alarm clock2/15/2024 ![]() This means that although during the day the display does The clock has 3 brightness levels to allow the display brightness to be adjusted to the user's preference, but theīrightness does not auto adjust with ambient light conditions. The display glows through fascia to display the time without the LED's being directly The Capello Clock is a cheap alarm clock with a wood grain fascia covering a display composed of small white LEDsĪrranged as 7 segment digits. Hack to make the cheap Capello alarm clock auto dim at night Use the Arduino IDE to program the ATTiny using the following code: /*** ![]() Detail showing how the modifications are wired in ATTiny on the back of the display, with the LDR mounted in a hole on the display frame Program This allows light to reach the LDR through the front of the display without making a hole through the outside of the clock. Drill the fascia panel from the underside at the spot the LDR touches it, until there is just the thickness of the wood effect vinyl covering the hole. Drill a hole in the display frame and hot glue the LDR into the hole. Mount the ATTiny in a socket which is hot glued to the back of the display, along with the resistors. ![]() The traces on the clock are cut at the places marked in the picture to disconnect the clock’s display signal at R6 and R7 from the drive transistors Q1 and Q2. Modifications to the Clock Detail of the clock PCB where we will make modifications Pin 8 will be connected to the clock’s Vcc which is 3.3v. Pin7 is analog input AD1 and will be connected to the LDR. Pin 6 is PB3 and will be connected to the clock’s resistor R7. Pin 5 is PB4 and will be connected to the the clock’s resistor R6. Pin 4 of the ATTiny will be connected to the clock’s ground. Pin 3 is PB0 and will be the output connected to the clock’s drive transistor Q1 for digit pair 1. Pin 2 is PB1 and will be the output connected to the clock’s drive transistor Q2 for digit pair 2. R6 and R7 connect the signals from the clock’s microcontroller (hidden under the display) to the two transistors Q1 and Q2 that drive the display. Remove the four screws in each corner of the display and then carefully pry it out from the case of the clock:Ĭarefully pry the 5 clips that attach the plastic frame to the circuit board to remove it. Use a pry tool or knife to carefully remove it. The front panel of the clock is about 2mm thick and held on with double sided tape. ![]() We will monitor the light level using a photoresistor or (light dependent resistor, LDR) connected to an Atmel ATTiny85 microcontroller and generate signals that decrease the amount of time the display is turned on when ambient light levels decrease. We will disconnect the clock’s signal lines from the transistors that drive the display segments and modify the signal to reduce the “on” time as ambient light in the room decreases. The display operates as two pairs of digits, whereby one pair is on while the other pair is off and they are switched on and off fast enough that the user does not perceive any flicker because of the LED’s residual glow and the user’s persistence of vision.Īt the bright setting the PWM duty cycle is 50% (ie an on time of approx 44ms), at the medium setting the on time is 1.4ms and at the dim setting the on time is approx. The clock has very few internal components – a single microcontroller and a few transistors and capacitors to drive the display using signals from the microcontroller. This project will make the Capello clock automatically dim at night. However, even the dimmest setting is quite bright at night in a dark room, and if you are sensitive to light at night, the issue is worse because the light is white, not a muted red or green. The clock has three different brightness levels, selected by pressing a button on the top. It features a 3 1/2 digit numerical display using white LEDs that glow through a woodgrain effect front panel. The Capello Big Time alarm clock is an attractive, inexpensive bedside clock commonly available at Target stores and online.
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