*Circuit Issues* DIGITAL ALARM CLOCK

Thread Starter

MissFluffy

Joined Oct 25, 2023
16
Hi everyone! I'm currently working on a digital alarm clock project and have used a website for reference: (https://bestengineeringprojects.com/digital-clock-with-seconds-and-alarm-time-display/) However, I've made some modifications, such as removing the transformer and some diodes. I've added a buzzer, a potentiometer, and a voltage regulator (7805). Currently, I'm using a 9V DC adapter, but since I'm just breadboarding everything for testing, I'm using a 9V power supply.

I've connected everything as shown in my schematic, but it seems not to be working. See the photo below:
*Note: I've also changed the capacitors in the original schematic from 47pF to 20pF since I am using an ATS042 4.9152 MHz ±30ppm Crystal 20pF 120 Ohms HC-49/US, which I bought from Digikey.

I'm open to any suggestions, comments, or advice about my schematic/circuit. I'm hoping to get this issue fixed as soon as possible
 

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Thread Starter

MissFluffy

Joined Oct 25, 2023
16
What isn't working?
I’m not getting square waves on pin 14 of IC5 and output of IC4 , all I’m getting is noise. One potential problem I considered was that I might have purchased a crystal oscillator with a different load capacitance than needed. The original schematic shows two 47 pF capacitors connected to the crystal oscillator, but the datasheet on Digikey specifies a load capacitance of 20 pF. So I replaced the 47 pF capacitors with 20 pF ones.
 

WBahn

Joined Mar 31, 2012
30,065
There's valuable lesson to be learned here -- you wired up this entire circuit and then applied power and hoped everything works. Yet you have a problem with the clock signal, which is the very first thing you should have gotten working.

Incremental build and test -- it pays off.

Remove everything from the clock generation portion of the circuit (you don't have to remove much, just the wire(s) where the clock signal is being used) and see what kind of clock signal you get, if any. Until you have a decent clock signal, there's no point going any further.
 

Audioguru again

Joined Oct 21, 2019
6,695
You cannot use 20pF capacitors on a breadboard that has a lot of stray capacitance from rows of contacts and wires all over the place. Many other circuits also will not work in a breadboard.
 

sarahMCML

Joined May 11, 2019
370
I’m not getting square waves on pin 14 of IC5 and output of IC4 , all I’m getting is noise. One potential problem I considered was that I might have purchased a crystal oscillator with a different load capacitance than needed. The original schematic shows two 47 pF capacitors connected to the crystal oscillator, but the datasheet on Digikey specifies a load capacitance of 20 pF. So I replaced the 47 pF capacitors with 20 pF ones.
If you're trying to use a standard CD4060 at 4.9152 MHz with a 5V supply you're exceeding it's designed operating specifications. You need to use a 74HC4060 version for such speeds at 5V.
 
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