# Solar Refrigerator Timers. 5min On Delay. And 50 Percent Swap.

#### N11778

Joined Dec 4, 2015
176
The 5 min Monostable on delay timer allows the Inverter to stop and start during short sun outages and not destroy the compressor.

The 30 min Astable Swap timer allows you to run two refrigerators without increasing the load on the system.
Most refrigerators only run 40 Percent of the time. They can be used with freezers also.

Timers use the old stand by NE555 timer and a low leakage Tantilum Capacitor C1.
They are line voltage operated, use caution working on them they are NOT isolated.

Use both of them in Series, 5 Min. Delay first, for two refrigerators or freezers.

In the Swap timer R7, Z2, D2, and D3, can be left out. They are there to make the first on time the same length as the following times.
Without them the first on time will be about 5 Min. longer.

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#### Bernard

Joined Aug 7, 2008
5,788
Thanks, I was contimplating something like that for when the grid went down, but that's still a way off

#### AnalogKid

Joined Aug 1, 2013
9,385
I think a 10 M resistor and a high-value, ultra-low-leakage capacitor are expensive and hard to get for many people. Here is an alternative to the 555 part of the circuit. It uses a single chip oscillator/divider to get accurate and repeatable long duration time periods from relative common components. The oscillator runs at approx 4.5 Hz. When divided by 16384, this produces a 1 hour period square wave, 30 minutes high and 30 minutes low, to drive the TRIAC gate. I added an LED at a little under 2 sec on, 2 sec off to show that the circuit is thinking. Note there is no need for 1% tolerance components; those are what's in my design library.

ak

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#### debe

Joined Sep 21, 2010
1,251
Bernard, if you want they are available on Ebay for $10 Aust for when the mains fails. This is one I have. Thread Starter #### N11778 Joined Dec 4, 2015 176 I think a 10 M resistor and a high-value, ultra-low-leakage capacitor are expensive and hard to get for many people. Here is an alternative to the 555 part of the circuit. It uses a single chip oscillator/divider to get accurate and repeatable long duration time periods from relative common components. The oscillator runs at approx 4.5 Hz. When divided by 16384, this produces a 1 hour period square wave, 30 minutes high and 30 minutes low, to drive the TRIAC gate. I added an LED at a little under 2 sec on, 2 sec off to show that the circuit is thinking. Note there is no need for 1% tolerance components; those are what's in my design library. ak View attachment 115331 Mikee Likes It. I did not know about the 6040. I have 5 on order ($3.75 for 5) for the next timer project.
Guess I should have posted my Idea, when I was googling and trying to figure it out.
I would have went your way .
Thanks for the post.
Sparky

#### AnalogKid

Joined Aug 1, 2013
9,385
The 4060 is my go-to part for loooong oscillator periods. For even longer periods, check out the CD4521. That part can time out to the 8-second range starting with a crystal oscillator for real precision.

Adding one signal diode turns it into an equally long monostable. The one quirk is that it always powers up running, not sitting there waiting for the first trigger, because the decoded output that inhibits it after the whatever delay hasn't happened yet. Still, for many applications it fits in nicely.

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