12V Power supplies...

[beelzerob]

So as I gather more little devices that seem to always require a 12v power supply...I begin to wonder if I can have a single power supply and just attach multiple devices to it....or if a wall wart for one device will work just as well for another device (since I seem to have acquired some spares).

Is it really just as easy as making sure that the required amperage for any attached devices is less than what the wall wart can supply?

If that's the case...then wouldn't a single PC power supply handle almost all devices? I have a ton of these things laying around. Granted, they would probably tend to use more power just sitting there than a wall wart would...but I bet a PC power supply could handle the load of maybe a dozen wall warts.

 

[icellama21]

In general DC voltage and current is pretty simple. 12V is 12V(usually a bit more, but that is OK), and you can just add up your max current needs(either measure or check the specs). A few things to keep in mind when picking a power supply:

1) Higher quality switching/rectification/voltage regulation. Some devices are more sensitive to their input power than others. Some devices work with a two dollar half-rectification transformer, others need a much cleaner supply. Go with a clean(hard to evaluate, but usually the more expensive switching varieties) and you'll avoid occasional unpredictability.

2) Make sure you have enough power. Many power supplies have large voltage drops(aka below 12V) as you near their power maximums. Keep some extra for the future.

3) Use good distribution. Don't try to run 5A through cat5, use appropriate wires.

4) If using a computer power supply be aware there are sometimes multiple 12V rails and each is current limited separately. You'll need to balance your loads. There are also 3.3, 5, -12, -5 and other voltages.

I never thought about it, but using a computer power supply is probably a good, cheap way to get high current that is clean. You can probably hook it up to a battery charging circuit for a backup too.

 

[icellama21]

Also, don't assume PC power supplies will take more power. AC power = Voltage X Current X PowerFactor. Some PC power supplies are highly efficient(greater than 95% energy converted to output instead of heat) and have active power factor correction to get the PF over 90% too. Also, forgot to mention that using too large a switching power supply can be inefficient, keep some extra capacity, but more than 2x the capacity is usually wasteful.

 

[KenM]

So as I gather more little devices that seem to always require a 12v power supply...I begin to wonder if I can have a single power supply and just attach multiple devices to it....or if a wall wart for one device will work just as well for another device (since I seem to have acquired some spares).

Is it really just as easy as making sure that the required amperage for any attached devices is less than what the wall wart can supply?

If that's the case...then wouldn't a single PC power supply handle almost all devices? I have a ton of these things laying around. Granted, they would probably tend to use more power just sitting there than a wall wart would...but I bet a PC power supply could handle the load of maybe a dozen wall warts.

Just Be Aware that some of the wall power 'transformers' are regulated, AND, some are not (the 'some' are only semi-regulated). I am not up to speed as to how things like cell phones want the power to be. You may turn a good electrical device into smoke by plugging in a 'semi-regulated' PS where it wanted a regulated PS. On the other hand (I think) using a regulated PS where a semi-regulated PS is needed will cause no problems. I have been using a small regulated (switchable voltage) power supply for fifteen years with good results. It may not charge the batteries as well, but, what the heck.

ken

 

[beelzerob]

Well, I'll have to tally up the warts I've got and see how much that is. I think a PC power supply will always be wasting power in the fan, if nothing else....I don't have any spare PC power supplies that use a temp controlled fan. Of course, being in the basement, I'd think I could just disable the fan altogether and see what happens....I'm sure I won't be pushing a 350w power supply to its breaking point running a datanab and an ocelot...

 

[beelzerob]

Just Be Aware that some of the wall power 'transformers' are regulated, AND, some are not (the 'some' are only semi-regulated). I am not up to speed as to how things like cell phones want the power to be. You may turn a good electrical device into smoke by plugging in a 'semi-regulated' PS where it wanted a regulated PS. On the other hand (I think) using a regulated PS where a semi-regulated PS is needed will cause no problems. I have been using a small regulated (switchable voltage) power supply for fifteen years with good results. It may not charge the batteries as well, but, what the heck.

ken

Regulated or unregulated...anyway to tell? Either on the wall wart or on a PC power supply?

 

[CollinR]

If you use an ATX power supply you need to short green to black to get it to fire off without a mainboard and put a load on the 5v rail. I dunno why just heard they will smoke if the 12v (yellow wires) rail gets loaded up with no load on the 5v (Red wires).

A decent fan is what I have used in the past, this is how I am testing my jeeputer right now, 350watt atx supply 1 12v rail will run my jeeputer, touchscreen, GPS reciever and USB keyboard/mouse.

Unfortunately unlike my CCTV power supplies you get almost exactly 12vdc so you have no room for voltage loss along the wire. Still it's quite a bit of power on the cheap and being residental you probably don't have too long of wire runs.

 

[KenM]

Regulated or unregulated...anyway to tell? Either on the wall wart or on a PC power supply?

The only way I know of for sure is to use a volt meter. A 12 volt regulated supply will probably measure between 11 and 13 volts. A semi-regulated 12 volt supply will read higher, it may read as high as 17 to 20 volts without a load. The semi-regulated supply relies on components in the device to do the final voltage regulation.

ken

 

[PaulD]

Google the phrase "converting computer power supply" and you will find a bunch of web sites that discuss the details and circuits on how to convert a standard computer supply into a power supply like you are interested in.

 

[Steve]

Personally, I would do something like this and then you can use a distribution board like this. You can usually find 8 port distribution boards. This is a similar supply (mine was only 4A) to what I got and will use to power all my PIR's, GB's, sirens, etc.

 

[beelzerob]

Darnit Steve, you have to be more careful than that. I almost bid on the distribution on the spot, just because it's (currently) so cheap. Never point me to a low priced ebay item!


So converting a PC power supply sounds interesting. Definitely along the "hobby" and "is work" lines, but still seems almost right on the edge of what I'd be capable of...and I seriously have at least 4 of these things just laying around.

So maybe converting a power supply...and THEN using the distribution panel? Is the distribution panel just for convenience, looks and (because of the fuzes) safety?

I'm going to do a wall-wart count tonight.

 

[gatchel]

Personally, I would do something like this and then you can use a distribution board like this. You can usually find 8 port distribution boards. This is a similar supply (mine was only 4A) to what I got and will use to power all my PIR's, GB's, sirens, etc.

The altronix part number is "PD8" for the 8 port. I use them all the time at work.

 

[Mike P]

Darnit Steve, you have to be more careful than that. I almost bid on the distribution on the spot, just because it's (currently) so cheap. Never point me to a low priced ebay item!


So converting a PC power supply sounds interesting. Definitely along the "hobby" and "is work" lines, but still seems almost right on the edge of what I'd be capable of...and I seriously have at least 4 of these things just laying around.

So maybe converting a power supply...and THEN using the distribution panel? Is the distribution panel just for convenience, looks and (because of the fuzes) safety?

I'm going to do a wall-wart count tonight.

beelzerob,

I have a bunch of Altornix AL400ULX power supplies, If you want one, let me know and I will put one up for sale on the for sale section. I also have some Altronix PD-8 dis. boards. These are 8 output boards that can be used with the 400 power supplies. I use these as well as 600(More amperage) in my set-up. Every device including 4 wire smokes in my system has its own fused output. They come in a can, But if you are short on space they can be removed from the can. Check the Altronix web site for details. I love these things, They make for a super clean installation.

Mike

 

[beelzerob]

I love these things, They make for a super clean installation.

Mike

HHAHAAHAHA. :lol:

Sorry. But if those are meant to be used to make a clean installation, then they'd probably self destruct as soon as I brought them into the room.

I really do have to start my showcase thread so people can see it and weep. The most organized thing I have is the full rack I just got which dates back to I think the early 70's. Otherwise, instead of cans, I have terminal blocks screwed to the wall. It works for me, but I had to spend some time the other night explaining to my wife that, no matter how cool she thinks it is, it's actually very ghetto by HA standards.

Anyway, I do appreciate the offer, and I'm rare to turn down an offer of getting some more equipment at a decent price (even if I hadn't needed it prior to, oh...NOW)....so let me make my accounting tonight of wall warts and see where I'm at.

I do like the idea of converting a PC power supply, just to be able to put one to use! but that does take time, and a certain amount of skill....both of which I'm in very short supply of.

Here's the bonus question for you smart guys out there, though....I notice in the pc power supply conversion thread I read through, that you end up with a +12V and a -12V output supply. If that's true...then could I bridge those to use that as a 24V power supply also? The rain8net I have has a 24v brick, and if I were to actually get the damper put in I'm thinking of, that would also require a 24v power supply. Would that work, or is it not that easy?

 

[Helheim]

Personally, I would do something like this and then you can use a distribution board like this. You can usually find 8 port distribution boards. This is a similar supply (mine was only 4A) to what I got and will use to power all my PIR's, GB's, sirens, etc.

That's what I have but haven't even used it yet.. http://my.webpix.ca/d/154-2/IMG_2622.jpg