Hey /diy/nos,
I'm trying to design a controller for a reef aquarium so the first thing I want to get figured out is switching AC devices on/off. I've done some research and most diyers use these relays as pictured or the solid state relays attached to a micro but I want something that I don't need to worry about failing or burning down my apartment complex.
I do have a few years with electronics but none really with mains power. Is it realistic to think I can basically make a controllable 8 outlet power strip and not have it be a fire risk?
I've been looking into some commercial controllable power strips and this seems like a good option but it looks like an ancient design: https://www.youtube.com/watch?v=s9odA7LH91c . There's also this: http://www.powerswitchtail.com/Pages/default.aspx but getting 6 or 8 might be a little pricey and I can see installation getting messy and a little cumbersome.
What do you guys think?
As long as you figure out how many amps are going to be flowing through the relays and you have relays rated for that current there shouldn't be a fire hazard. Though, relays aren't really meant to be constantly energized so that may be a problem if you're planning to use them as a switch that's going to be on for a long time.
>>947756
If you lived in Dallas, I'd give you 8 idecs and bases.
Look up idec (name brand) or icecube relays. You don't have to have bases, but they make it easier to mount. Those or RIBs are we use in a professional setting 99% of the time.
>Track mount relays are the last option, and only use them when space is the primary concern.
>>947756
if you design can be clock based, use pic related
>>947762
>relays aren't really meant to be constantly energized
citation?
OP here
>>947762
I'm sort of basing my caution on the fact that almost every tutorial working with these relays tell the user not to use without supervision and training ect ect. There's also the connectors, wires and and traces that need to be highly rated which makes me reluctant to start experimenting.
>>947774
I'm in NY actually but thanks for the suggestion, I now have a bunch more to research. Any pros and cons with ice cube vs RIBS? What is wrong with track mount and is the track mount a type of base? Overall these options are a lot better than the relay module?
>>947784
Yes those are nice and I've used them before but I want to use some process control so everything really needs to be digital.
Thanks everyone
>>947807
only the final relay which switches the main power needs to have a high-amp rating. your control wiring should be low volt, low amp.
a relay-in-a-box is going to cost the most. as far as mounting, you can get ice cubes with flanges so you can screw them to an enclosure. track mount i think he means DIN rail, which is nice but probably not something you need.
you would get better advice if we knew the scope of your project and how/what you want to control.
>>947784
Relays are electromagnets, keeping one powered for a long time will saturate it and mess up with the values of current it can work with.
>>947807
You could use a transformer to insulate your electronic circuit from the AC part.
You do everything electronic related on low volt/amp and then use signal output to activate the relay through the transformer since it will protect your electronic parts.
>>947835
If relays aren't optimal, maybe OP could rectify the AC coming from a transformer and use a mosfet to switch it on/off instead
>>947823
Ok some more details about the project. Everything is ballpark but should give you an idea. Devices plugged into the wall are:
-200 watt commercial led lighting unit, switched on and off morning and night
-50 watt water heater, control scheme to regulate temperature. Switched on and off maybe every 20min?
-50 watt water pump, mostly always on
-20 watt water pump, mostly always on
DC units are
- Up to 3 12v peristaltic pumps for dosing and water topoff. Maybe on a few minutes a day each.
So nothing high speed and I could get away with using manual switches with a few components but it would be nice to have the digital option.
>>947835
I plan to have something like a 12v dc power supply regulated down for the ICs and for the dc pumps. I agree it should be no problem managing the control signal, I'm comfortable with that.
Thanks
Months ago I made a circuit to do AC switching and be programmable. It uses 4 triacs and has 3 relays. It's still working. A triac will die instantly if you short it, a relay won't, so you'll probably have to rely on your circuit breaker to prevent fires or something like that. It's still working.
>>947852
I'v been looking into this myself. Its hard to do nicely without spending a bunch. Relays like OP pic are the most straight forward but can be a problem to drive from a micro controller as the current draw is usually too high.
best thing to do is control a mosfet that controls a relay. that way your circuits have good separation and youre not straining the micro controller for power requirements.
>>947756
triac, dude
>>947947
how can you control a triac with a micro controller and have it switch mains voltage?
>>948053
Opto-triacs used to drive the main triacs.
Any benefits of a triac? It seems like the popular solution is a relay.
>>948225
Triacs don't have moving parts, they won't wear out from being switched frequently, they don't generate RF interference when switching, etc. And you can switch at the zero-crossing point, which is sometimes useful.
Op here
I tried out the mechanical relays and I think the clicking is going to be a bit much so I'm looking into solid state relays.
Is it a bad idea to get chinese units off ebay for like 1/4 the price digikey parts?
I had a setup for a year or two using the clickey relays. I went the route of buying the plug-into-the-wall type of RF remote relays, then just deconstructed them and spliced the wires for my kitchen/livingroom/etc lights into them. Already built to handle that kind of power, so pretty safe. Then instead of using the shitty remotes that came with them (and only controlled a few units at a time) I just used an arduino board w/ RF receive/transmit ability (you can get an easy 25-35$ unit from Ray's Hoby called RF Toy i think), and used that to control them all. Had about 8 -10 units throughout the house controlling lights, so your setup is easily doable. Ultimately had the arduino board connected via USB to my desktop/house-brain PC, then just used a little autohotkey script to send signals through COM port to allow me to control the house lights with my desktop. from there you can write scripts to adjust timing or whatever you desire, even get a shitty phone app capable of hitting taskbar icons, and then just pin a shortcut to your script to the taskbar.
Like I said, pretty safe route, the clickiness never bothered me, and since the relays are built with wall-plug-in in mind, there little danger of sucking it up/fire. Just splice it good and use the little screw on caps or tape for safety.
In the end, 5-8$ per relay unit, 25-35$ or the arduino board with RF send/receive ability. Def cheaper than a commercial home automation route, and fun as fuck to build tinker with. Just took the system down, bout to move, and you can reuse/retweak the hardware as you want for years to come.
Manufaturer of relays i think was Etekcity or someshitty chinese thing, they come in packs of 3-5 with a remote (just get one, you're gonna use it to steal the RF code anyway).
>>948836
How did you figure out what the remotes are emitting and then copy that with the RF module?
>>948817
They're hit and miss, but for the price you can upsize bit and buy a few extras for half the price of a professional quality one. At my work we have a box of cheap Chinese parts that we use for prototyping and fucking around, but anything that goes to a client we purchase from Mouser or Digikey so we know it works when it needs to.
