Timer

[wjwong]

i am stuck on how to ON my project every 1hour?
Hope for some clue.....

[low5545]

first you need a microcontroller.

[shahrul]

For timing, I think you need RTC. This is suitable design.

[wjwong]

i thinking of doing 60s delay and looping 6o times is that possible? RTC is a burden to add on to my project instead i choose timer 555 and decade counter as hardware control.

60s Delay with PIC16F877A 20MHz
is there any example for delay program and looping?

[shahrul]

RTC is very easy, if you know.
Easily can program what to do for every hour.

For delay, you can use

CODE: SELECT_ALL_CODE

for(i=0;i<3600;i++) __delay_ms(1000); //delay 1 hour


[sich]

Shahrul is right that using the RTC is really simple. You can refer to this DIY project.

If you're using delay to get the time, the error will increase over time. Moreover, you can't do anything while the delay is counting...it means that within the one hour, your system is just working on the delay loop and nothing productive can be done.

Timer interrupt is more advisable to be used compared to delay function, if you don't want to use the RTC chip. Some microcontroller also has RTC module built-in. You can have a look in Microchip's product tree too.

[wjwong]

Thanks for the advise. Yeap i am considering and going to start study on it.

RTC capable to trigger my project every 1 hour? Just slightly confirmation.
Anyways thanks alot

[sich]

RTC capable to trigger my project every 1 hour? Just slightly confirmation.

RTC keeps the time and your program will need to retrieve the current time from the RTC. So it's your program which triggers certain function when the time is up.

[yonghui]

RTC is real time clock, for sure it can do the task.

if no precise timing is required, __delay_ms() with Hitech compiler can do the task.
or else u can use the available timers in the PIC to do counting and keep accumulating the time in a variable. and compared it while loop to trigger hourly.

if u have microcontroller which has the internal RTC like new PIC18F u can use the function in RTC to generate interrupt to wake and trigger.

regards,
yh

[ABSF]

i thinking of doing 60s delay and looping 6o times is that possible? RTC is a burden to add on to my project instead i choose timer 555 and decade counter as hardware control.

60s Delay with PIC16F877A 20MHz
is there any example for delay program and looping?

It's not so easy and not accurate to generate 60 second pulses using 555 timer. You may generate shorter duration pulses and further divide them down using counters like 4020, 4040 or 4060 (dont need 555 as there is a built in osc). You can even cascade the 4040 to make longer chain of dividers to finally get 3600 second pulse. connect the out put to one of the RB ports (IIRC) which has edge trigger function. It can trigger an interrupt when it senses H-L or L-H edge.

Or just set up the 555 to generate 1 second pulse and connect it to RB0. On every pulse let there be an interrupt (has to setup the SFR properly). Set up two counters (CountH and countL)to increment the pulses in the ISR() till it reaches 3600 then set the variable One_Hour_Flag high. Your main routine would poll this flag to see if time is up to start up your project.

Or you can even do the above without the 555 timer. Just use the 16-bit TMR1 inside the PIC. Refer to this link to see how to do it

viewtopic.php?f=21&t=10676&p=13420&hilit=interrupt#p13420

Allen