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Light timer

 
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Markdem



Joined: 24 Jun 2005
Posts: 206

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Light timer
PostPosted: Sat Jan 28, 2006 3:15 am     Reply with quote
Hi All, i am tring to get a simple light timer working. I am testing the time from a ds1307 by the following statment

Code:

(currenthrs >= on_hour[i] && currenthrs <= off_hour[i] && currentmin >= on_min[i] && currentmin < off_min[i])


This all works OK, it the off_min is bigger then the on_min
on time 19.10 off time 19.50.

But if i try
on time 19.10 off time 20.01, it will not work. I can seem to come up with a good test statment.

Any one have any ideas??

Thanks, Mark
Eric Minbiole



Joined: 10 Jun 2004
Posts: 16
Location: USA

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PostPosted: Sat Jan 28, 2006 7:29 am     Reply with quote
To make the logic easier, I would make a small helper routine that simply compares two times, taking into account that hours are more significant than minutes. The example below returns +1 if A>B, -1 if A<B, and 0 if they are equal:

Code:

signed int8 CompareTime(int8 hourA, int8 minA, int8 hourB, int8 minB)
{
    // compare hours first
    if (hourA > hourB)
        return 1;  // time A > time B
    if (hourA < hourB)
        return -1  // time A < time B

    // hours equal: compare minutes
    if (minA > minB)
        return 1;  // time A > time B
    if (minA < minB)
        return -1; // time A < time B

    // both times equal
    return 0
}


Then, in your main code, do something like this:

Code:

if ((CompareTime(currenthrs, currentmin, on_hour[i], on_min[i]) >= 0) &&
    (CompareTime(currenthrs, currentmin, off_hour[i], off_min[i]) <= 0))
{
  // current time is within start/stop times: turn on lamp
}


Also, creating a structure that has both hours & minutes together might help clean up the code, too. Hope this helps!
J1M



Joined: 15 Feb 2005
Posts: 21

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PostPosted: Sat Jan 28, 2006 8:04 am     Reply with quote
Hi, in my page www.hobbypic.com ive uploaded a project called TerraPIC, its a controller for terrariums or small conservatories ;), project has a hygrostat, termostat, and two timers. This timers makes that you are looking for ;)

best regards
Markdem



Joined: 24 Jun 2005
Posts: 206

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PostPosted: Sun Jan 29, 2006 1:32 am     Reply with quote
Hello all, Eric Minbiole, thanks for the code, but it is still doing the same as my code. If the off min time is leas then the on min time, it will not go on.

J1M, i cant seem to download your code for the ftp. Could you please upload it here??

Thanks Mark
J1M



Joined: 15 Feb 2005
Posts: 21

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PostPosted: Sun Jan 29, 2006 3:23 am     Reply with quote
Hi Mark,

Try clickin secondary button and click on 'Save Link As', works ok Smile

regards
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