# Info on alarm/bell circuit

Discussion in 'The Projects Forum' started by dstroya, May 15, 2012.

1. ### dstroya Thread Starter New Member

May 15, 2012
1
0
Hi guys,I am new to this site.I am currently busy with my Electro Tech course.I need help regarding a project.I am finding some
difiiculty because I did not do any Microcontrollers yet.I need to build a circuit that rings an alarm or bell at certain times.
The bell has to ring at
a)8:00 am
b)9:45am
c)10:00
d)11:45
e)12:15
f)14:00
It must run from Monday -Thursday 8am-2pm
friday
8am-12pm
Sat and sun it must be off.
It must also have a backup battery which must always maintain its charge.

I am not asking you guys to build the project for me.I just need guidelines.I am thinking of using 555 timers and counters
but don't know how to integrate it.
Your assistance will highly be appreciated

2. ### wayneh Expert

Sep 9, 2010
15,250
5,579
Not a good choice for this, IMHO. I think you'd do much better using a crystal oscillator for your "clock", as the precision will be MUCH better than anything you can do with a 555-based clock, which will drift around due to temperature.

3. ### mcasale Active Member

Jul 18, 2011
210
12
There are so many Arduino or Basic Stamp projects out there. You should be able to find a clock project and then glom on the bells and whistles. It's a better learning experience, too.

Otherwise, you'll need a good oscillator chip and a bunch of counters and/or shift registers. It'll be much more difficult.

4. ### Bernard AAC Fanatic!

Aug 7, 2008
4,954
553
The shortest time period seems to be 15 min., so starting with a 15 min. clock divide by 4, periods in an hour; div. by 12, hours in a day, div by 2 AM-PM, div by 7 days.; all with 5 4022's. The rest is a bunch of OR gates, like a 4 input for Mon-Thurs., then for 8AM a 3 in , combined days, 8, AM = Bell. For Fri. the 5 time periods & Fri.
For clock divide line to 15 min, or hack a quartz clock for 38? kHz and rivide even further to 15 min.
Bring all outputs to a socket strip so that you can pick a choose.

Last edited: May 15, 2012
5. ### Bernard AAC Fanatic!

Aug 7, 2008
4,954
553
Sorry- left out the AND gates. How long should bell ring? Might start with A 4060 IC, clock & 14 stage divider, and add more accurate clock later if necessary. Consider running ckt from 7 AA Ni-Cd cells with 6 V regulator, trickle charge from wall wart.