Simplest to Build Alarm Clock

Simple clock based on the SC3610D and LCD. It can be configured to work as alarm clock or radio frequency counter. The clock can be used as single device or embedded in AM/FM radios acting as display of the current frequency, adding an alarm clock function, when the radio is off. To work as clock it needs only three main parts : SC3610D chip, small LCD and clock quartz crystal.

The SC3610 is a frequency and clock display driver used for displaying FM/AM radio frequency or a 12 hour alarm clock. By using CMOS technology, it consumes very low power in clock display mode.

FEATURES

* FM input with pre-scalar for radio frequency up to 150 MHz

* AM input for radio frequency up to 30 MHz

* 3 common, 13 segment, 1/3 bias LCD display drivers which supports 4 digits LCD display

* On chip oscillator for external 32.768kHz crystal

* 10.7 MHz / 70 kHz I.F. frequency offset for FM signal and 455kHz I.F. frequency offset for AM signal

* Internal real time clock in 12 hour display mode

* Selectable clock or frequency display

* 1.8V to 3.3V supply voltage

The chip is able to drive directly the LCD. The only required additional part is the quartz crystal. All other devices are optional. Most of the chip inputs has embedded pull-up or pull-down resistors, which define the default settings. These resistors can be overdriven by other resistors (4.7 kOhm should be OK) connected to the opposite rail, if different setting than the default is required. These pins can be also dynamically switched by external microcontroller or switch if needed.

Based on the mentioned chip and LCD, I have created a simple multifunctional alarm clock. It can be configured to work as clock or AM/FM frequency counter for radio. It has the two needed inputs for the AM or FM frequency and two control inputs to select

1. the mode: clock or frequency counter
2. the AM or FM radio receiver

Five small tactile buttons are used to :

1. Set the time (when hold pressed and the buttons "Hours" and "Min" are toggled)
2. Set the alarm time - works in the same way as Time set button
3. Hours - set hours
4. Min - set minutes
5. Alarm On/Off - activates/deactivates the alarm

As alarm I use universal passive buzzer.

The PCB for the clock has dimensions 43mmx35mm. It was produced and delivered by PCBway within a week. It can be ordered here.

Here is the BOM :

Part Value Package Comment

C1 15p C0805

C2 100n C0805

C3 15p C0805

C4 2-5p C0805

C5 3-5p C0805

C6 100n C0805

D13 SOD323-R diode

Q5 TC26H crystal

R1 R0805

R2 R0805

R3 4.7k R0805

R4 R0805

R5 4.7k R0805

R6 4.7k R0805

S1 Alarm On/Off DTSM-3 switch-tact

S2 Alarm Set DTSM-3 switch-tact

S3 Min DTSM-3 switch-tact

S4 Hours DTSM-3 switch-tact

S5 Time Set DTSM-3 switch-tact

SG1 F/QMX F/QMX buzzer MR270

U$1 MINI_LCD MINI_LCD Mini_LCD_SC3610D

U$2 SC3610D SC3610D SC3610D

The resistors with empty values can be also 4.7kOhm, or simply bridged with solder.

The clock is very simple and works fine. The alarm sound is quite quit - you cold try to use some other piezo speaker.Have in mind that the maximum supply voltage of the chip is 3.3V - the clock can be supplied by two 1.5V AA or AAA batteries or 3.3V voltage regulator (for example AMS1117-3.3V)