Teeny tiny exhaust fan – time delay switch
Hi all,
We re-use milk bags, ziploc bags, and other plastic paraphernalia. This involves washing them, which involves drying them. They are an ugly thing to have hanging in your kitchen drying, so I turned a small 5″ wide space between cabinets into a little drying cupboard.
My current plan is to use a old cooling fan from a computer tower to ventilate this little cupboard into the toekick space, to speed up the drying process in a closed cupboard. I’d like to be able to have the fan turn on automatically whenever the door is opened and then stay on for an adjustable time period, likely over an hour. I was going to convert the fan to run off 120v via one of the many methods shown on youtube. But I can’t find something I could use as a cupboard switch with a time delay.
Electrical finagling is not my specialty…any ideas would be appreciated.
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Not sure how you're going to control the logic. Via arduino or a premade timer board, but a few switches I can think of that might work like proximity sensors or magnet sensors that can act as a switch or input when you open the cabinet door.
Why not just use a bathroom fan timer? You'd have to press the button to start it, but other than that, it does what you want. Something like:
https://www.amazon.com/Enerlites-HET06-Countdown-Switch-Bathroom/dp/B01LYQV7B8/
Simple and off the shelf. Run the output to a receptacle, probably in the same 2 gang box, and plug your 12v fan power supply into that.
You can use a security-style magnetic door switch to detect door openings, something like this: https://www.mpja.com/Mag-Switch-SPDT-With-Magnet/productinfo/31514+SW/. You can use that switch to trigger a time delay relay such as model #21EP67 from Grainger (http://www.grainger.com).
All you need is a 12v DC power supply (https://www.mpja.com/12-Volt-DC-Adapter-Power-Supply-1A-Cisco/productinfo/33381+PS/) to power the relay through the switch. Mount everything in a regular electrical box with a receptacle on top. Use that to control your fan.
This is a pretty simple project, you don't need any fancy programmable stuff.
I've actually built something similar to this to activate pantry lighting whenever the pantry door is opened. The only difference is I don't have any time delay since that's not needed with the lights.
Bill
Ah! The time delay relay, that's what was missing. I'm sure I can find something similar available in Canada. Something like this maybe: https://www.amazon.ca/Infinite-Timing-0-15min-0-60min-Adjustable/dp/B075581Q58/ref=pd_sbs_469_7?_encoding=UTF8&pd_rd_i=B075581Q58&pd_rd_r=4be7ccfa-0494-4d52-8bb0-dcbe85e66231&pd_rd_w=QWE7j&pd_rd_wg=S2vdZ&pf_rd_p=dbebb38c-0e3d-4a67-ac15-432d7c7a2789&pf_rd_r=3QNEMB46ANA6J2SKT7JP&psc=1&refRID=3QNEMB46ANA6J2SKT7JP Thanks!!! Excuse my ignorance (really out of my depth but how else do you learn to swim?) but how do I size the power supply for it? Do you need something that exactly matches the power requirements of the fan?
If you want to power a 12v DC fan, you need a 12v DC power supply that provides AT LEAST the amount of current that the fan requires. The fan will have a label something like "12V DC 0.17A". That means 12 volts DC, 0.17 amps. You need a power supply that provides 12v DC, and AT LEAST 0.17A. Any extra power (higher amperage) rating on the power supply is fine. The 1 amp supply in the link I posted would be a good fit for you, especially for only $5. MPJA probably won't have a problem shipping to Canada either. They're always easy to deal with, I've ordered from them many times.
The time delay relay in your link will probably work just fine too.
Note that if you get a little plastic enclosure and a few LEDs (a "power" and a "FAN ON" LED), you can make a very nice little system for your fan controller.
Bill
Thanks, that clears it up! I can probably hunt down an old power supply around here then...
That would be very nice, although I don't know where I would get an enclosure or LEDs. Google here I come!
Be careful buying component level parts like LEDs from googled sources. That includes amazon and eBay in many cases. Many of the parts found there are counterfeit or otherwise compromised (low quality, knockoffs, etc). Buy from reputable places.
The MPJA site I linked to is a surplus place that has been around a long time. I’ve ordered from them many times. All Electronics in California is another similar place.
Some real electronics suppliers are digikey (http://www.digikey.com) and mouser (http://www.mouser.com). These places will have top quality parts and they have good prices. Digikey I know no longer has a minimum order, and they’ll have everything you need — although MPJA will be cheaper for the power supply. I’m sure digikey will ship to Canada too.
Future electronics is a Canadian electronic component distributor. It’s been a long time since I used them, but they’re probably still around. I think they’re in Quebec somewhere but I don’t remember for sure.
Bill
Thanks Bill, that's really helpful info. All kinds of cool stuff available from those suppliers...I'm going to need more spare time :D
MPJA doesn't ship outside the USA. Luckily, power supplies like these are pretty common.
Digikey has a dedicated Canadian site: http://www.digikey.ca
Definitely go to that site, because while you can order from the .com site, you will get screwed on import fees.
I agree with the suggestion of just a simple timer. Won't there be times when you get bags out but don't add any? I don't think I'd want the fan to run every single time the door was opened. You can also get 120Vac fans in the same size as the ones from computer power supplies. If you have a surplus store or Princess Auto near you, you can pick one up for just a few dollars.
We do the same thing with Ziploc bags. We just wash them inside out and "tent" them on top of the sink drain board (or on top of any dishes already drying there).
The fan draws such little power, it won't matter if it runs every time. I'd really like it to be automatic, because otherwise it won't get used. Then I'll have a musty smelling cupboard...
Search Mcmaster.com for a "Socket-Mount Multifunction Timer Relays" Part # 6964k16 $110 plus socket
Thanks Tim!
Yupster,
I've never done this before, so I don't know if what I'm going to suggest below will work for sure. But I'm sure others can comment. I do think a 120vac bath timer is probably most people's easiest.
But if I were to do it. I might buy something like this one: https://www.amazon.ca/6V-30V-Multifunction-Trigger-Control-Display/dp/B07CYMTM5R
you get way more options with this board. The board itself is a little more complicated, but it affords some simplicities in other aspects... For instance, you can power it with a cellphone charger:
https://www.amazon.ca/AUKEY-Charger-Portable-Foldable-Compatible/dp/B01M0EOZ3L
Then a fan like this, goes in the other slot of the charger. https://www.amazon.ca/GDSTIME-7530-Brushless-Blower-Cooling/dp/B07SWJPXNS
Where the power cord of the fan, I'd strip and wire it to the output relay of the board.
The I'd get these magnet sensors as the input because they already come with wire. I'd wire one of them to the input on the board
https://www.amazon.ca/Uxcell-a14060400ux0169-Magnetic-Door-Switch/dp/B00PZMG980
Not the simplest solution, but cheap, cheerful and keeps it low volatge. I like little custom builds like this that handles a specific problem.
I like that relay, that's a great idea! Sound like it would work to me, thanks!
I recently installed a tiny fan from AC Infinity in a kitchen cabinet to send a tiny amount of air into a very tight space behind a built-in refrigerator. The build-up of heat behind the fridge was causing the compressor to run too hot, and there wasn't a good way to get air back there passively, so I put in the fan to give it a boost. It works great. It cost about $35, and seems to be very high quality. They're dead quiet, designed for cooling stereo and computer racks. The company also sells timers, I think, but I haven't tried them.
Nice, thanks for the heads up!