Generating a pulse every certain number of hours, Developing IC and

[LuisGtz]

Hi, I'm trying to design a low price electronic circuit that triggers an audible alarm every certain amount of hours (1, 4, 6, 8, 12 or 24). Once I have the complete design on a protoboard I would try to send it to a company such as TI, in order they can manufacture all the circuit in a single chip. My Idea is to attach this circuit into a tape, so it has to be of very little size. However it is the first time I try to do something like this and have little idea.

I designed one circuit using a NE555 in astable mode, with RA=2.2Mohms, RB=1.49Mohms and C=1000microF, in order it can generate a pulse each hour. Then I connected the output of this circuit to another NE555, this one monostable, that would gave a pulse for 10 seconds in order to activate an alarm during this time of period (I used a capacitor, a transistor, and some resistors to couple the output of the first NE555 with the trigger of the second one and have the correct polarization).

I know NE555 are not designed to work at frequencies so small, but I don't know what other IC I can used to generate a pulse every hour or every 12 hours. I don't want to use a microprocessor because it would be more expensive. I had already build a circuit with a time period of 3600 seconds (1 hour) and connected it to a PC to monitor how exact it is, the results have being (4766, 3775, 3707, 3675, 3655, and still trying) as you can see the error is decrementing each time.


Another problem I'm Facing is that I would like to use a small battery to feed the system, I found a 3V battery from Panasonic with very small dimentions, however NE555 function with minimum 4.5 volts.

Do you know if a company dedicated to built IC can desing me a circuit with the characteristics I want, that can operate only with 3V?

Finally, I don't know if there is a chip you can recommend me, cheap and easy to get, that can generate a beep alarm o certain melody, or if would be better to use a buzzer piezoelectric of very small size. I found one from CUI of only a couple of centimeters (less than one inch in diameter)is there any other option? What kind of speaker does the musical greeting cards had? I tried to buy one of this cards, but they are not being sell in my country anymore.

I would appreciate ALL your comments or ideas.

 

[nbucska]

Making a dedicated ( ASIC ) IC is expensive -- think
$50,000 to $100,000 or more.

Cheap solution would be to take apart a cheap wristwatch
and use its LCD inputs to drive some logic.

at about $10 you could use a XILINX FPGA but software
is $$$$ .


<nbucska@pcperipherals.com>

 

[LuisGtz]

I know that making an ASIC is expensive, but if I can have an efficient IC and my company's marketing department aproves it, we would have a big volume (1 million maybe) so, the price per IC would low, am I rigth?

 

[nbucska]

send detailed spec's -- Do you want NDA ?

<nbucska@pcperipherals.com>

 

[melone]

Doesn't your system already have some sort of &quot;brains&quot; in it? If so, why doesn't that generate the signal?

 

[designchain]

32,768 Hz crystal into a transistor to drive a string of 74HC4040s (or a couple relatively simple PLDs wired as a 32 bit counter or a single PLD with 32 registers you can configure as a counter). Even with a million a year I'd do the math since you can do this with a single chip anyway...

 

[nbucska]

What is your target price per ea? Do you have other electronic function ? Using a cheap ucontroller may be
a better alternative !

<nbucska@pcperipherals.com>

 

[amidabadi]

the 4060 with interna osc with a 3276800 hz crystal give 1 hz on Q14 then divide by 4040 and use some and gate to get your output