3 month countdown alarm (miniature circuit)

Thread Starter

MLD

Joined Dec 7, 2012
76
Hello Everyone,

Im trying to build a 3 month countdown timer alarm in the smallest miniature form there possibly is using the smallest electronic components. Trying to use the smallest battery like a watch battery or smaller, I would like the timer countdown to start right after I apply power to the battery then sound a buzzer after the countdown has been completed. Id like the buzzer to be the smallest and very low consumption.

If anyone can help me supply me a schematic diagram and the parts list it would be great that way I can go ahead and build it and test it.

Thank You All.
 

AnalogKid

Joined Aug 1, 2013
9,362
OR, you could supply me with a block diagram and schematic of what you have so far, tell me if this can use a microcontroller or must be all discrete hardware, information about what accuracy you need, the type of display, any switches or controls, how the device will be packaged, what environment it will be used in, and basically everything I need to do all of the work for you.

Based on your description, a PIC10F200T-I/OT will do this for 42 cents.

ak
 
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DickCappels

Joined Aug 21, 2008
7,746
A long time ago I read an application note for this very thing. It was a timer to indicate when it is time to replace air filters in office buildings. The solution presented in the application note was a microcontroller with on-chip clock generator.
 

AnalogKid

Joined Aug 1, 2013
9,362
The PIC has an internal clock oscillator factory trimmed to 1%, so the period might be 89 or 91 days. For another 10 cents there's one with1/3 the operating current for even longer battery life. Scarey what you can get in a SOT-5 package. Is my memory conflating things or does someone make a 3-pin uC?

ak
 

Thread Starter

MLD

Joined Dec 7, 2012
76
3 months is the time of the countdown. Not adjustable. Does not have to be exactly precise at 3 months but close. As small as miniature as possible. No switches, no displays. Simplicity. Smallest and most economical as possible. It will be at room temperature and normal atmosphere. It will not be exposed to rain or humidity.
 

Bernard

Joined Aug 7, 2008
5,788
As I'm stuck in the past, I would use 2 SMT 4060's, buzzer driver, & a few R's & a C. First 4060, stage counts up to 24 hours, 2'nd counts to 2048, but to avoid decoding, tweek colck to give 2160 hours @ 12 th stage, which on resetting causes 13 th stage to go high, turning on buzzer. What turns buzzer off?? Guessing about 40 mA hr. for battery, excluding buzzer.
 

Dodgydave

Joined Jun 22, 2012
10,050
Here is a programme using a pic12f675 for three months, sets two outputs to go complimentary after time limit , then stops, use it to feed your buzzer.

the pic is a 8 pin dil, works from 3-5V dc, i am sure you can modify it for other smaller pics if you want.
 

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AnalogKid

Joined Aug 1, 2013
9,362
As I'm stuck in the past, I would use 2 SMT 4060's, buzzer driver, & a few R's & a C. First 4060, stage counts up to 24 hours, 2'nd counts to 2048, but to avoid decoding, tweek colck to give 2160 hours @ 12 th stage, which on resetting causes 13 th stage to go high, turning on buzzer. What turns buzzer off?? Guessing about 40 mA hr. for battery, excluding buzzer.
My first thoughts also. But some jobs cry out for a uC, and a 38 bit counter plus a beeper seemed to be one of them.

ak
 

Thread Starter

MLD

Joined Dec 7, 2012
76
BOM: Battery, decoupling cap, PIC, beeper.
Have two of the PIC output drive a piezo beeper and there's nothing left to do but the firmware.

ak
AK, what will be the smallest parts to use PIC, CAP, BATTERY, BUZZER I usually buy my parts at digikey, can you supply me with a parts list from digikey? Can you provide me with the schematic diagram and the firmware, id like to build this and test it by the end of this month. THANKS
 

Thread Starter

MLD

Joined Dec 7, 2012
76
Here is a programme using a pic12f675 for three months, sets two outputs to go complimentary after time limit , then stops, use it to feed your buzzer.

the pic is a 8 pin dil, works from 3-5V dc, i am sure you can modify it for other smaller pics if you want.
Dave,

I have either the Top Max II or the Chip Max II programmer by EE tools, I have to check which is the one I have for sure, can I use that to program the PIC? Problem on my programmer I only have the DIP socket, is there a cheaper programmer I can buy online or ebay to program the smaller mini surface mount PIC?
Thanks
 

Thread Starter

MLD

Joined Dec 7, 2012
76
As I'm stuck in the past, I would use 2 SMT 4060's, buzzer driver, & a few R's & a C. First 4060, stage counts up to 24 hours, 2'nd counts to 2048, but to avoid decoding, tweek colck to give 2160 hours @ 12 th stage, which on resetting causes 13 th stage to go high, turning on buzzer. What turns buzzer off?? Guessing about 40 mA hr. for battery, excluding buzzer.
Bernard,

Im trying to use as least components as possible and the smallest there is. Forgot to ADD one thing WHAT TURNS THE BUZZER OFF. I might need to add a mini push or slide switch, didn't think of that.
 
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