A/C Energy Saver

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A/C Energy Saver

Postby matseng » Thu Aug 16, 2012 5:05 am

This is an "intervalometer" made for your air conditioner. I live in Kuala Lumpur just three degrees north of the equator - a rather hot and humid place. Since I don't really like a/c's I tend to just use floor and ceiling fans to keep cool. But the bedroom gets a bit too humid during some nights so I wake up every now and then and turn on the a/c for a few minutes to dry up the air a bit in the room.

This device can be set to automatically send the on/off IR-code to the a/c at regular intervals between set hours. Like run the a/c for 5 minutes every other hour between 11pm and 9 am.

Powered by a small lipo battery and having the PicoPower version of the ATMEGA48PA it should be able to run for months between charges (usb charger is on board).

The board has a "ghetto" version of four 7-segment displays where each segment is made up by two smd 0805 leds.

It also includes a IR decoder for learning the on/off code in case the remote code is not already included in the firmware.

The PCB is a Sick-Of-Beige DP7043 design so I can easily get a nice looking enclosure for it.

I'll send the gerbers to Seeed for a prototype batch next week when I'm done routing the leds.

ACsaver-render.png
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Re: A/C Energy Saver

Postby arakis » Fri Aug 17, 2012 3:06 am

Nice project, will you release the source code/design files.
I'f you need any help wiht the case, I'll be happy to oblige..
best regards FIlip.
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Re: A/C Energy Saver

Postby systemstech » Fri Aug 17, 2012 9:04 am

This is nice. Replace that old thermostat with this and you could read in the dark from about five feet away, just change the red leds to white and bingo there you go. :) I want one just for the leds.
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Re: A/C Energy Saver

Postby matseng » Fri Aug 17, 2012 9:28 am

Arakis: I'll put up the files at github soon, but I won't start doing the firmware until I have received the boards. I'll try to do the case myself, but I'd appreciate if you could give it a check to see if I've screwed it up too bad :-/

Systemstech: The cpu is meant to go into deep sleep with only the internal rtc running (750 nA power consumption) most of the time. The leds would only be lit when setting the parameters or the battery would be drained too quickly. But it would be easy to implement a mode where the leds are always lit when the charging cable is plugged in to the usb port.
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Re: A/C Energy Saver

Postby systemstech » Fri Aug 17, 2012 10:04 am

I like your design, I would add blue tooth so that I can change the settings via my phone and put it in a clear thermostat case mounted on the wall as art and function. I'll wait for the files and see if I can think of some more stuff to add to it to make it my own.
Great idea.
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Re: A/C Energy Saver

Postby dps » Fri Aug 17, 2012 11:32 pm

YES! Such a project has been on my "maybe to-do" list for quite some time. Mine would support precise on and off times (multiple) and an onboard thermometer for better thermostat-ing.

Maybe some day... which probably will end up being after I no longer have a window A/C that needs the remote! :p
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Re: A/C Energy Saver

Postby matseng » Sat Aug 18, 2012 3:53 am

Hmmm.. A thermometer might be nice to include on the board. Unfortunately I've already run out of I/O's on the ATmega and had to do a ugly hack to share the ports for the led cathode drivers and the reading of the buttons. But with some more uglyness I should be able to fit in a temp sensor as well.
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Re: A/C Energy Saver

Postby matseng » Mon Aug 20, 2012 5:45 am

dps: Thank you for the idea of having a temp sensor on the board. I added an LM75 but I had to do some creative untested sharing of pins on the ATmega. If it works it will be like a bonus functionality of the board - if not, no harm is done :-)

The design files are available at Github; https://github.com/SmallRoomLabs/ACsaver I'll send the gerbers to Seeed in a couple of days...

ACsaver-v4.png
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Re: A/C Energy Saver

Postby dps » Thu Oct 25, 2012 9:20 am

matseng: You're welcome! It's cool to see one's ideas included! :-)

Any luck building up the boards?
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Re: A/C Energy Saver

Postby matseng » Mon Oct 29, 2012 3:05 am

Nah, not yet... I forgot this in my last order of pcb's. So it will be in the next order together with the bugfix-revisions for the last order.
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