I'm going to be running a series of electrical outlets in my crawl space - and want to have an arduino selectively switch power from the outlet to a set of plugs. Each of the outlets in the string have 2 outlets, 1 will need to go to the arduino as the source of the switched power, and I was originally going to put a 9v A/C wall wart in the other to power the unit.
However, I didn't want 8 or 10 wall wart running - that would be a hugh waste of energy converting the AC to 9 DC
So, I am considering running a low voltage run along with the AC lines and tap each unit off this line.
What would be the best power supply that would supply enough 9v power to handle 10 units? So I will only have
one wall wart instead of 10. I just want to minimize the amount of wasted electricity - since this will run 24/7.
I'd prefer a plug n play - vs having to build one.
Forgot to add: I'll need enough power for the arduino, an RF receiver and two relays that will be switched - for each unit
One power supply isn't necessarily more efficient than 10 power supplies. And, if you use switching supplies (or one switching power supply) they are nearly 100% efficient.
You'll need to measure (or estimate) the current required for each Arduino in your particular application. I don't know what the current requirement for the Arduino alone is, but I'm sure someone can tell you. Thenyou'll ned to know the current requirements for the RF module and relays. And, leave yourself some safety margin. A power supply with extra current capability won't be any less efficient and it will be more reliable.
So, I am considering running a low voltage run along with the AC lines and tap each unit off this line.
If you can run wires in parallel with the AC line, you probably don't need 10 Arduino's.
BTW - And I'm not sure what you are doing, but you can buy "home automation" systems such as [u]X-10[/u] or [u]Insteon[/u]. I've got an X-10 controller/timer and 8 or 10 X-10 controlled lights & outlets. The controller get's programmed by the computer and it turns-on my porch lights at sunset, etc. And, I've got a couple of manual controllers, so I can press a button an turn on/of everything that's X-10 controlled.
I've also got a "sunrise simulation" gizmo I built with a microcontroller that slowly fades-on the light with a "gentle beeper" that wakes me up in the morning. That gizmo doesn't have it's own time-of-day clock, so it's plugged into the X-10. (With the Insteon dimmers, you don't need the gizmo because you can actually dim-up in steps to simulate fading-on the light over several minutes.)
You can interface the Arduino with the X-10 protocol, but I've never tried it.
If you are concerned with power efficiency, run the Arduino from a 5V switching supply. The on-board regulator is linear and at 9V almost as much power is wasted in the regulator as the Arduino is using. (At 10V, the regulator is consuming exactly the same amount of power as everything running from it! i.e. 50% efficiency.)
If you need 9V for something else you can use two power supplies or a dual power supply.
Having 1 p/s vs 10 has the advantages of - I was hoping for a power supply I could
just plug in and have two wires out.
the outlets won't be in areas that are easy to get to - so having only one p/s to
worry about. nice.
I seemed to think that 10 p/s (1a) would lose more electricity in heat converting
the 120a/c -> 9v dc than one p/s would - but that might not be the case just
seemed like it would be.
As for not needed 10 boards - I thought about that - and running the individual trigger
wires to each relay - then I'd need like a 10-12 conductor wire, and as the farther you
go on the string, you would need less wires. So for consistency it would be better if
all I needed to do was tap into the 9v and the AC plug - the box would be pre-addressed
with it's "address" - and would monitor the RF signal for any packets for it - which
would tell it to activate/deactive an AC outlet .
For space I'm using a nano board.
But the more ideas, the more the project evolves.....
I don't see the need for more than one Arduino. One Arduino Uno can control 10 relays. Keep them all near to the Arduino and run all your mains cables from this central position. That way, all your control stuff is in one place for ease of maintenance, and I'm sure that a Uno, a PSU, an RC unit and ten lengths of mains cable is a lot cheaper than 10 Nanos, 10 PSUs and 10 RC units.
I thought about doing the single controller - but then to do runs of electrical lines to each is a lot wiring.
I want to do one run of a string of outlets - and have each unit plugged into an outlet and will have
control over what is plugged into it.
This way if that unit's function is no longer needed - it's still a normal outlet.
As for cost - I'm not sure it might be even , if not more expensive to run separate mains. I would have to add
in a large junction box - not to mention now each main can only control one output - whereas with separate
units, I could put in a 2, 3 or 4 relay - not to mention it would look like an electricians nightmare to see a junction
box with 10 sets of mains running out of it and god forbid the insurance nightmare if there was ever any
damage from that - they most likely wouldn't pay - a Major factor to consider!
As for not needed 10 boards - I thought about that - and running the individual trigger
wires to each relay - then I'd need like a 10-12 conductor wire, and as the farther you
go on the string, you would need less wires.
Telephone systems and computer networks usually have a separate cable running from each "terminal" to a central "hub". To me, that seems like the most practical solution (unless you want to use X-10).
I've seen multiconductor cable used in telephone/telecom systems, but it can be a mess where you "tap in".
But, it's your project and you get to make all of the decisions and compromises!
I thought about the telephone system cabling - which I would most likely have gone with rs232 (not ribbon) cable which has around 10 conductors - going higher than it starts to get a little higher in per foot charge - that would allow me to have one controller and trigger the relay(s) from one spot with the low power cable, but one of the features of the system I wanted to put in was giving each unit and address that can be triggered by RF - so placement doesn't matter, and for that matter could
be put anywhere in the range of the RF transmitter if need be.
Just as If I decided to run the 5-9v from one power supply, then I'd need (most likely) a thicker gauge wire to handle the
higher draw along that cable from all the units - that an rs232 (or a cat5/6 cable) might be able to safely carry - that, I'd have to experiment with to see how hot the wires get with the full draw.
Although I am more leaning now, to putting in a small power supply inside each unit to tap off the A/C input - Just not sure if I want the boards being powered off the same lines that are getting switched - if there is any spikes - so having a separate low voltage power line might be an advantage there.
Lots of things to consider, need to make sure everything is safe first.
gginnj:
I thought about the telephone system cabling - which I would most likely have gone with rs232 (not ribbon) cable which has around 10 conductors
No such thing as RS-232 cable.
I would have thought you were referring to "Cat 5" cable, but you mention that in passing. That is of course, 8 conductors and would be the overall cheapest option for your application. Suspect you are thinking of telephone multi-pair cable such as 5 pair (10 wires), 6 pair or 10 pair.
Suggest you use SSRs (only 20 mA or so to control each), and if you are dabbling with the possibility of running a low voltage power supply from place to place, then it will be much more practical to use the multi-pair cable instead to operate the SSRs from a central point. Assembling multiple Pro Minis together with relays at each location (and housing them) and implementing a communication protocol between them will complicate things immensely and your "plug and play" concept will come back to bite you.
In case you are wondering, I wired my house to have all (light and fan) points cabled back to a single central relay box. I will most likely be using Pro Minis for each control point (switchplate, but touch).
Granted, RS232 is a protocol....It was D-Sub 25 pin connector - that had 25 wire cable (usually ribbon cable) - but most only had 10 or so wires since not all pins were used - these weren't twisted pairs - separate wires.
And then they had that monster telephone cable that had 40 or 50 wires - forget the connector type - it was used to
connect multi-line phones (those with 8 or 10 lines)
