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I like using led strips to create various pieces of lighting around the house for myself and also for friends. I buy the cheap 3528 analog reels from Amazon, (the stuff that gets shipped straight from China), and I go to Goodwill or other thrift stores and find small 12v plug-in power supplies to run them. I don't know what some of the classifications mean though, or which ones I should, or should not, use.
For instance, some say "class 2", while others don't state a class classification at all. And a lot say I.T.E. use only. I did Google that and found that it stands for information technology equipment, but what does that really mean?? Can those only be used with equipment that turns on and off constantly rather than staying on for very long? Are either of these types okay? Our should they be avoided? Are there any other markings that I should be looking for? Thanks for the help.

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  • \$\begingroup\$ V = Volts. | I = Amps = current. | mA = 1/1000th of an amp so eg 500 mA = 0.5A. | PSU = power supply unit = plugpack = wallwart. | Power in Watts = W = V x I || PSU Watts should be >= (greater than or equal) to LED strip Watts rating. | Watts of LEDs may be specified by supplier. Watts = V x I (Volts x Amps). PSU will say Watts or 12V at eg 500 mA or 2A or whatever. 500 mA = 0.5A. Power = V x I = eg 12V x 0.5A = 6W or 12V x 2A = 24W etc. APPROXIMATELY LED power = 1/4 Watt per "section" of strip if 3 LEDS per section (based on std current of 0.02A/LED BUT this may vary | .... \$\endgroup\$ – Russell McMahon Jan 2 '15 at 10:52
  • \$\begingroup\$ .... Sometimes they use 3 LEDS in one pack and occasionally 3 x 3 LED pkgs = 9 LEDS/section. For 9 LEDs/section power ~~= 3/4 W/section . | LEDS may specify Watts per metre. Current can be measured with multimeter (part of DMM = digital multimeter. | IF psu volts are 12V +/- 0.5V unloaded and sags only slightly (say 0.5V) when loaded it is probably OK. | Ideally psu will run warm to cool. If it gets toasty hot it's overloaded. \$\endgroup\$ – Russell McMahon Jan 2 '15 at 10:54
  • \$\begingroup\$ possible duplicate of Choosing power supply, how to get the voltage and current ratings? \$\endgroup\$ – Passerby Mar 3 '15 at 20:13
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There's a company called UL that certifies electrical devices for safety and publishes several standards related to electrical safety. You can read about Class 2 Power Units in more detail but in general they are isolated and should be a good choice for safety.

Personally for the sake of saving a few dollars I'd stick with a power supply that has been UL certified rather than one of unknown origin / safety and it should have a mark such as the following:

UL Logos

You're correct that I.T.E stands for information technology equipment. There's a related question here Why are laptop power supplies marked “IT equipment only”? and while they may work OK you'd be best to avoid using them for other purposes.

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  • \$\begingroup\$ Thank you, this helps. I am aware of UL, and I do only buy psu's that are UL listed. That part has kind of seemed like a no-brainer. I'll definitely go and read the articles you linked to. For some reason I seem to think there was a third designation that I commonly saw on power supplies, but none of the ones I have on hand have it (if, in fact, there is a third...). Other than making sure they're CLASS 2, UL LISTED, can you think of anything else I should look out for? Thank you again for the help. \$\endgroup\$ – Jeff A Jan 2 '15 at 20:38
  • \$\begingroup\$ Hi Jeff, you may be thinking of a CE mark. That covers safety and issues with interfering with other equipment and is required to sell in Europe, there's a lot of overlap so you'll find a product will often carry both so it can be sold globally but I think for the USA just the UL certification should be sufficient. I guess the only other thing to keep in mind is while it's illegal in most countries if you but really cheap imported ones from e-bay and the like the marks can be counterfeit, it may be best to stick with a reputable supplier instead so that's less likely. \$\endgroup\$ – PeterJ Jan 2 '15 at 21:52
  • \$\begingroup\$ That makes sense. And I do want to start selling some of my pieces, so ya, I will definitely make sure I'm providing a safe and reliable power supply with them. After all, my name will be on the line right along with other people's safety... Thanks for the help guys. Cheers! \$\endgroup\$ – Jeff A Jan 4 '15 at 17:37
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Glossary:

V = Volts.
I = Amps = current.
mA = 1/1000th of an amp so eg 500 mA = 0.5A.
PSU = power supply unit = plugpack = wallwart.
Power in Watts = W = V x I


PSU Watts should be >= (greater than or equal) to LED strip Watts rating.
Watts of LEDs may be specified by supplier.
Watts = V x I (Volts x Amps).
PSU will say Watts or 12V at eg 500 mA or 2A or whatever.
500 mA = 0.5A.
Power = V x I = eg 12V x 0.5A = 6W or 12V x 2A = 24W etc.

APPROXIMATELY LED power = 1/4 Watt per "section" of strip if 3 LEDS per section (based on std current of 0.02A/LED BUT this may vary

Sometimes they use 3 LEDS in one pack and occasionally 3 x 3 LED pkgs = 9 LEDS/section.
For 9 LEDs/section power ~~= 3/4 W/section at 20 mA.
LEDS may specify Watts per metre.

Current can be measured with multimeter (part of DMM = digital multimeter.
Use 10A range for more than 200 mA = most strips.

IF psu volts = 12V +/- 0.5V unloaded and sags only slightly (say 0.5V) when loaded it is probably OK.

Ideally psu will run warm to cool.
If it gets toasty hot it's overloaded don't use it OR use for shorter strip.

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  • \$\begingroup\$ Wow, that was quite the reply, and took a while to write up, I'm sure. Thank you for that. It's not quite what I was asking though. I know how to calculate the wattage and amperage, I'm just not sure what TYPE of power supply to use, meaning, should it be class 2, or is there a reason that it specifically SHOULD NOT be class 2? Can I use ones marked as ITE ONLY, or is there a reason that I definitely SHOULD NOT use those? Your reply did have other useful information tho, acronyms in particular. So again, thank you, I do appreciate it. \$\endgroup\$ – Jeff A Jan 2 '15 at 20:26

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