how to interface an external timer and changing the timer value on run time

Hello Everyone,

I want change the timer value during run time. How should i do that? I also wanted to see timer value on LCD module ? How should i do that? Suppose initially i had given timer value as 10sec and later on during run time i want to change the timer value to 20sec, and these values i have to see on the LCD . Please help in me doing it.

Hello ,

I will try to explain you what am working on, There are two motor initially i will give some 10 sec delay between both the motor and this delay should be displayed on lcd. Then after some time i need to set timer for 30 sec between these motor which will also be displayed on lcd. This is like HMI ( human machine interface ) externally i want to change the timer according to my need.

well, so it's not an external timer...
its just two timers with respective output pins and a LCD for actual time display hopefully a microcontroller for the task...

so, how do you plan to set the new time?
-by an keypad connected to the microcontroller
- or by an external HMI (rs232?)
- or by a few buttons (up / down or something....)



sorry, from my point of view (from the microcontroller side) you must implement two programmable delays... you must set the outputs to some kind of switching device (a common Relay? or transistor?) and make an interface to a LCD.. then another interface to the input method


If you don't know how to do these things...
mmm
first: choose a microcontroller
seccond: learn that microcontroller..
third: search or design a programmable timed Delay (just a count down register... it's easy)
fourth: search or design a LCD interface (a common HDT44780 is almost for any microcontroller)
fifth: implement the input method to change the programmable timed Delay.
sixth: test an re-test!!!

any questions?

the approach and complexity will depend on details of your project but Kurenai_ryu has given you a pretty good approach.

I would suggest that before you start down that path, you may think about what kind of motors you intend to use, how they can be controlled and how you intend to control them. Many things can be done with a mcu but not everything needs to be done with a mcu.

many times, knowing what you want gets you half of the way there.

Thanks kurenai_ryu for this valuable reply......

i will tell you what exactly i want to do -
my aim is to switch on and off of a valve . initially there will be some delay let say 10 sec of delay between two valve. so when my system is on i will be able to see the delay value on the LCD. The process will continue. Now after some time i want to increase or decrease the timer value with the help of a push button , this value will be shown on the LCD. this is the total task .

Now what should i do. i am thinking for AT89c51 microcontroller and i will write the program in C language. So what would you suggest ?

like anything in life, you start small.

ask yourself if you can turn on / off a valve, if you can read a push button, if you can control a delay process, and if you can display something on an lcd. if you cannot do one of those, focus your efforts there until you can.

once you are able to do all of it, come back and ask people help to put it together.

i want to start a timer in 89c51 after a 10 usec pulse is given by pin p1.1 then timer wil continue to count the time and stop when it gets low on pin p1.2 , basicaly pin p1.2 is initialy LOW i want to stop the timer when it goes from low to HIGH and then again low after that i want to stop the timer and also i want to use that TIMER value for further process

plz can any buddy help me out for the source code of that

thanks in advance

---------- Post added at 12:20 ---------- Previous post was at 12:12 ----------

i want to start a timer in 89c51in such a way that timer wil start after a 10 usec puls is given from pin p1.1 ,on the rising edge or dosent mater on the falling edge of this puls then continue to count the time and stop when it gets low on pin p1.2 , basicaly pin p1.2 is initialy LOW i want to stop the timer when it goes from low to HIGH and then again low after that i want to stop the timer and also i want to use that TIMER value for further process

plz can any buddy help me out for the source code in ASSEMBLY LANGUAGE of that

thanks in advance