just_another_user
New Member
I've also been searching for a 28 day timer and hit this thread a few times. Nothing simple and economic turned up. Eventually I figured out a way to implement this, so I thought I'd share with everyone.
I needed a 28 day timer to turn on an appliance every fourth weekend. I have not made this yet but here is the plan...
I will get a 7 day digital timer. Every Saturday morning at 12:00am it will turn on for 3 hours. Then every Sunday night at 12 midnight it will turn on for 3 hours. Thus over a weekend it will turn on for a total of 6 hours, and over 4 weeks it will go a full 24 hours.
Now, a 24 hour mechanical timer has both the motor AND the output connected to the input, so the timer needs to be opened and modified to connect only the motor to the output of the 7 day digital timer. The simplest way is to connect a lead from the motor which plugs directly into the 7 day timer. The rest of the internals with mechanical switching of input to output can remain as is - just plug into a socket and plug in your load.
Since the timing of my application is not so critical I will offset the actual switching of the intended load by 1.5 hours - that is, it will turn on right in the middle of the second last 3 hour run time (18-21 hours) at 19:30, and off in the middle of the last 3 hour run time (21-24 hours) at 22:30. This will also ensure reliable operation since if one timer is switched even a fraction of a second before the other one then it could throw out the whole timing.
So that translates to a turn on time of 1:30am on the fourth Saturday and a turn off time of time of 1:30am on the morning following the fourth Sunday. Some adaptation may be needed to suit others' applications though, but it should be achievable. Perhaps another 24 hour timer (without modification) to switch on a load once a day for a short duration, a one-shot timer, or whatever.
I needed a 28 day timer to turn on an appliance every fourth weekend. I have not made this yet but here is the plan...
I will get a 7 day digital timer. Every Saturday morning at 12:00am it will turn on for 3 hours. Then every Sunday night at 12 midnight it will turn on for 3 hours. Thus over a weekend it will turn on for a total of 6 hours, and over 4 weeks it will go a full 24 hours.
Now, a 24 hour mechanical timer has both the motor AND the output connected to the input, so the timer needs to be opened and modified to connect only the motor to the output of the 7 day digital timer. The simplest way is to connect a lead from the motor which plugs directly into the 7 day timer. The rest of the internals with mechanical switching of input to output can remain as is - just plug into a socket and plug in your load.
Since the timing of my application is not so critical I will offset the actual switching of the intended load by 1.5 hours - that is, it will turn on right in the middle of the second last 3 hour run time (18-21 hours) at 19:30, and off in the middle of the last 3 hour run time (21-24 hours) at 22:30. This will also ensure reliable operation since if one timer is switched even a fraction of a second before the other one then it could throw out the whole timing.
So that translates to a turn on time of 1:30am on the fourth Saturday and a turn off time of time of 1:30am on the morning following the fourth Sunday. Some adaptation may be needed to suit others' applications though, but it should be achievable. Perhaps another 24 hour timer (without modification) to switch on a load once a day for a short duration, a one-shot timer, or whatever.
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