Long Duration Timer

[albertson]

I am trying to build a long duration timer as part of a bigger project. I found one at QKits Electronic Kits with their model QK152. A bit surprised (but should not have been as it was a "KIT", when it came and it was in pieces! I put it together and it does everything I want it to do but the max time delay is 8192 seconds or about 22 hours. It says the values for R1 and C1 can be changed to make longer times but they have no chart. I need the timer to count to 690,000 seconds or about 8 days +/- 10%.

They say you can put two kits together to get up to 20 years but it will make my overall project to expensive.

Can anyone recommend values for R1 and C1 that would be compatable with the 555 chip?

Thanks for any help, Doug

 

[KMoffett]

Can you post a schematic or a link to the manual. How accurate do you need the timer? +/-seconds?...minutes?...hours?

Ken

 

[albertson]

Thanks for the help! Here is the Schematic and parts list for the timer I built. The accuracy is not very important. I will be looking for the unit to reset every 7 days from an outside set of contacts that open if a test is successful. If it has not reset by 8 days, then this timer will send a text message saying the test did not happen. Long and short, +/- 3 or 4 hours would be fine.

Hope you can come up with somethings and happy holidays

Doug

 

[MrDEB]

this link sound exactly like your circuit

**broken link removed**
the 4020 can be cascaded in a chain so bascally just an additional 4020 needs to be added on.
for $13 you got a fair deal considering it includes a pc board.
just porcure a protype board from ? (radio shack) but you still need a 4020.
pretty simple design.
An actual schematic would be good then someone here can direct you on connecting the second 4020

 

[KMoffett]

Changing C1 from 1.0uF to 10.0uF will increase the time period by a factor of ~10.

Ken

 

[albertson]

Thanks for the help. I will purchase the cap. today and try it out.

Merry Christmas.

Doug

 

[rmn_tech]

Use a PIC it's so much easier, less components and as long a delay as you want. µ seconds to hundreds of years.

 

[albertson]

rmn_tech

I am open for anything if it is easier and cheaper as I have to be able to supply 100s of these things. What is a PIC and is it commercially available.

Thanks Doug

 

[KMoffett]

If you have to do 100, I would agree with the PIC approach.

Ken

 

[albertson]

I need 200 hours +/- so where do I purchase this PIC?

Also, I need an inexpensive phone dialer that can be programed to send a 10 to 20 second message or a text message that I can couple with the timer.

Any ideas? Everything I see on line is +$50

Thanks

Doug

 

[KMoffett]

PICs are microcontrollers that run of of 3-5VDC power supplies, have several inputs and outputs, and require programming. The chips are dirt cheap, but require a programmer interfaced to a computer, software to write the program, and someone that can do it. For that many, you can have that hired out...probably someone here..for a reasonable price.

Ken

 

[Boncuk]

I am trying to build a long duration timer as part of a bigger project. I found one at QKits Electronic Kits with their model QK152. A bit surprised (but should not have been as it was a "KIT", when it came and it was in pieces! I put it together and it does everything I want it to do but the max time delay is 8192 seconds or about 22 hours. It says the values for R1 and C1 can be changed to make longer times but they have no chart. I need the timer to count to 690,000 seconds or about 8 days +/- 10%.

They say you can put two kits together to get up to 20 years but it will make my overall project to expensive.

Can anyone recommend values for R1 and C1 that would be compatable with the 555 chip?

Thanks for any help, Doug

Hi Doug,

8192 seconds do not equal about 22 hours, but 2.2755~ hours.

Did you consider this? (1 hour = 60mins, 1min = 60 secs) 8192/3,600=2.2755~

 

[KMoffett]

Boncuk,

A typo, then a calculation using that error on the OP's part. From the manual:

If you change the count to 10 seconds then a maximum timer delay of 81920 seconds, or 22.7 hours, can be obtained.

Ken

 

[Pommie]

Just to give you an idea about pics, the 12F683 (an 8 pin pic) in quantities of 100 are $1.22 each. It would need no external components except a resistor to keep reset high. With the following code pin 7 will go high after 8 days +/- 1%. The external circuit should pull pin 3 low to reset the circuit.

#include <system.h>
#pragma DATA _CONFIG, _MCLRE_ON&_WDT_OFF&_INTOSCIO
#pragma CLOCK_FREQ 4000000

#define Cycles 1000000/8/10             //cycles for 100mS

volatile int ccpr1 @CCPR1L;

void main(){ 
unsigned char   tenths=0,seconds=0,minutes=0,
                hours=0,days=0;
    gpio=0;
    cmcon0=0;
    ansel=0;
    trisio = 0b11111110;                //GP0 output
    t1con = 0b00110001;                 //timer 1 on and pre=8
    ccpr1 = Cycles;                     //interupt every 10th second
    ccp1con=0b1011;                     //special event trigger
    while(1){                           //loop forever
        while(!pir1.CCP1IF);            //wait for time up
        pir1.CCP1IF=0;                  //clear bit
        if(++tenths==10){
            tenths=0;
            if(++seconds==60){
                seconds=0;
                if(++minutes==60){
                    minutes=0;
                    if(++hours==24){
                        hours=0;
                        days++;
                    }
                }
            }
        }
    }
    if(days==8){
        //time up
        gpio.0=1;
    }
}

It's a bit of a steep learning curve to get into pics but well worth it. They are very flexible.

The above code is C for the free BoostC compiler and is untested but should work.

And, as it's Christmas, you even get free code.

Mike.

 

[Dr. Mjh]

thanks

Thanks for the help. I will purchase the cap. today and try it out.

Merry Christmas.

Doug

thanks for being with the knowledge seeker.