90 day countdown timer

[riksworld]

Hi All,

I am looking at making a countdown timer that is set at 3 months to 0 to remind me to change my filter media.

I did think about using a 555 timer, but over this time period it might prove to be inaccurate.

The project will be powered by 2 aa or a 9v battery with 2 leds, 1 red and 1 green, the green led will stay on for 3 months, then go off and swop to the red led to indicate its time.

Ive been searching on google, but its now showing much up, can anyone on here please point me in the right direction.

Many thanks to all who replys.

 

[CocaCola]

Don't know if there is a commercial offering, this is easy enough to accomplish with a micro and a few LEDs, but then again you need to be setup to do this... As you suggest the 555 will drift all over that place over that period of time...

 

[riksworld]

thanks for your reply.

If you could recommend a micro, parts and how to program it, I will be willing to give it go.

 

[BobK]

What is your experience with microcontrollers?

Bob

 

[riksworld]

I have done a little, not much

 

[BobK]

Are you set up with tools to program any particular type?

Bob

 

[riksworld]

no, but if its cheap enough I will purchase a programmer

 

[BobK]

If you don't want to dive head first into micro development, a PICAXE is a good choice. It needs only a serial port (or USB to serial converter) to program and the software is free and it is programmed in a BASIC like language. There are several forum members here who have experience with them (not me, though)

Bob

 

[MrEE]

use your calendar or appointment book. easy.

 

[wingnut]

Don't cellphones and pc's have appointment reminders?

From experience I would recommend the Arduino Uno for ease of starting, but it won't work for this because the programmer and chip will be tied up for 3 months as they are one unit.

Next easiest is the Pickit 2/3 with a Pickit3 programmer (not MPLAB) and Mikrobasic. Use almost any PIC chip, I like the PIC16F628.

It would be only a few lines of code.

Picaxe code does not look any easier than any other code. Maybe the programmer is cheaper than others and that is its attraction.

 

[(*steve*)]

PICaxe is *way* easier (nowhere near as powerful though).

Still, it's powerful enough for a lot of tasks

edit: including this one.

I believe that long period timing using this chip uses the watchdog timer to allow the device to sleep for an extended period (up to 2.3 seconds or thereabouts) and you do that lots of times to get your 24 hour delay (which is repeated 90 times). Timing accuracy is not too great, but probably OK for a "replace XXX now" message that will be fine if it's out by a bit.

If you want to-the-minute accuracy you'll need crystal control and a little more power. If you want to go to this extent, then the PICaxe is probably not what you want.