Sunday, April 5, 2009

Hour Alarm Clock

This hour alarm clock will work nicely as a real time clock with a backup battery & also it will give you an alarm notification on every hour. This hour alarm clock show time in 12 hour clock format.

Features

*Accurate Timekeeping
*AM/PM Indicator
*Hourly Chime
*Key Press Tone
*Power Sense / Display Off
*Battery Backup

How to Adjust Time

There are two switches, Hour switch & minute switch. Press & hold the corresponding switch & it will automatically increment the display value. When the correct value (time) comes released the switch. While pressing you may also hear a key press tone for a short period time.

Note: when adjust the time it will reset the seconds to zero “00” automatically so you can keep the time to the exact second.

AM/PM Indicator

Every 12 hour the AM/PM led will toggles. You can change the state of this Led by adjusting the hour switch.

Power Sense / Display Off

There is a separate input for power sense. It will always monitor the external power is present or not. I have placed a CR2032 coin cell battery to compact the overall design. You can use two AA alkaline batteries.

If the external power is present the clock will work normally with all the features. (Hour Alarm, Key Press, AM/PM etc...)

If the external power is not available it will shift to backup battery & keep the time running without getting switched off. When the clock is running from backup battery, the display will be switched off & all the features will be disabled. So only the internal clock program will run in this mode.

When the external power comes it will give you an alarm notification & start powering from external power mode. Now the display will start displaying the present time & the clock will work with all the other features.

Piezo Diaphragm

You need a piezo diaphragm (without built-in oscillator). Which means it has only diaphragm & requires an AC waveform or pulsed-DC to produce a sound.

The other type piezo is a piezo diaphragm with built-in circuitry which only require dc source to generate the sound.

You need the first type piezo above mentioned. If you cannot find such as mentioned you can use a small speaker instead.
 






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