Author Topic: How do you tell what "type" of power a DC power supply is?  (Read 6756 times)

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Offline DW1961Topic starter

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #25 on: July 24, 2020, 07:38:29 pm »
Anyone who does anything at all with electronics should have a multimeter, even if it's just a basic $20 model. A bench power supply with CV and CC modes is very handy but there are substitutes you can use in a pinch to accomplish most things.

I have three DMMs. All capable of doing current test. What could I use for a power source instead of getting a bench supply? I mean, they're like $120.00 bucks on Amazon.
 

Offline DW1961Topic starter

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #26 on: July 24, 2020, 07:40:54 pm »
Might be just for regulation and applied standards reasons.

Lighting is a different kind of equipment than e.g. a general purpose power brick, so it's tested and declared conforming to different standards.

^^^ This.

If a power supply is sold with a CE mark, then it's sold as being compliant with all applicable standards.

If the set of standards which apply is different - say, because it's being used with computing, communications or other equipment, instead of the type of equipment for which its testing and certification applies - then it's no longer compliant.

Good information, but why does that power supply I linked to above have  a CE mark on it and say "LED use only?" Also, how could you test it to make sure it is compliant? I'd love to know that. Does complaint mean ripple and etc are in spec?
 

Offline John B

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #27 on: July 24, 2020, 08:35:29 pm »
For the same reason it says UL LIGTED, all it proves is that they have a silkscreen printer. Hence why I try to stick to industrial brand name supplies from legit suppliers.
 

Offline DW1961Topic starter

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #28 on: July 24, 2020, 09:04:27 pm »
For the same reason it says UL LIGTED, all it proves is that they have a silkscreen printer. Hence why I try to stick to industrial brand name supplies from legit suppliers.

lol, yep. I guess the only way to test it is to put it under load and xx heat and scope it. I don't have that ability, sadly. It would be interesting to see exactly what it's doing.

I know I'm going to have to get a scope and learn how to use it to test stuff like this. I just want to KNOW!
 

Offline james_s

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #29 on: July 25, 2020, 04:57:07 am »
If you have any serious interest in electronics you should get a scope, they've gotten really cheap, relatively speaking. A decent 4 channel scope costs less than most smartphones these days.

 
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Offline AndyC_772

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #30 on: July 25, 2020, 06:55:42 am »
Good information, but why does that power supply I linked to above have  a CE mark on it and say "LED use only?" Also, how could you test it to make sure it is compliant? I'd love to know that. Does complaint mean ripple and etc are in spec?

The standards in question relate to EMC (radio interference) and safety, not functionality. The ripple voltage, for example, could be atrocious, but that wouldn't make it non-compliant from a legal standpoint.

To test it properly, you'd need to take it to an approvals lab where they'd put it in a screened enclosure, connect it to a load (which in this case is an LED lighting strip) and measure the radio emissions from it. It's also tested for its conducted emissions back up the mains cable, immunity to spikes, surges and drop-outs in the mains supply, and immunity to radio interference generated by other nearby equipment.

In terms of safety they'll look at things like electrical isolation between the mains and the low voltage output, the temperature of the case when it's under full load, flammability, current leakage to earth, and whether or not it's correctly marked with voltage and current ratings, type of fuse and so on. A lot of the process is about paperwork.
 
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Offline DW1961Topic starter

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #31 on: July 25, 2020, 05:04:35 pm »
If you have any serious interest in electronics you should get a scope, they've gotten really cheap, relatively speaking. A decent 4 channel scope costs less than most smartphones these days.

I've noticed bench power supplies (adjustable) are really cheap on Amazon. Any suggestions under 110.00 bucks? Same for scopes, but they seems like they start around 400+.
 

Offline DW1961Topic starter

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #32 on: July 25, 2020, 05:08:52 pm »
Good information, but why does that power supply I linked to above have  a CE mark on it and say "LED use only?" Also, how could you test it to make sure it is compliant? I'd love to know that. Does complaint mean ripple and etc are in spec?

The standards in question relate to EMC (radio interference) and safety, not functionality. The ripple voltage, for example, could be atrocious, but that wouldn't make it non-compliant from a legal standpoint.

To test it properly, you'd need to take it to an approvals lab where they'd put it in a screened enclosure, connect it to a load (which in this case is an LED lighting strip) and measure the radio emissions from it. It's also tested for its conducted emissions back up the mains cable, immunity to spikes, surges and drop-outs in the mains supply, and immunity to radio interference generated by other nearby equipment.

In terms of safety they'll look at things like electrical isolation between the mains and the low voltage output, the temperature of the case when it's under full load, flammability, current leakage to earth, and whether or not it's correctly marked with voltage and current ratings, type of fuse and so on. A lot of the process is about paperwork.

Got it. I would hope those PSU would at least be safe. A scope could test for voltage and ripple and other undesirable, though, correct? I'm less worried about burning to death than protecting my equipment :)
 

Offline james_s

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #33 on: July 25, 2020, 05:41:43 pm »
I've noticed bench power supplies (adjustable) are really cheap on Amazon. Any suggestions under 110.00 bucks? Same for scopes, but they seems like they start around 400+.

The cheapest decent new scope I'm aware of is the Rigol DS1054z which is trivial to hack to 100MHz and costs $349 from Tequipment, that's dirt cheap for a scope.

On a tighter budget there are some 2 channel models from Rigol and Siglent, or if you have space for a "boat anchor" and don't mind a gamble on used gear, I've seen 1990s CRT digital scopes from A-list brands like Tek and HP go for as little as $100. Then there are old analog scopes, you might get lucky and score one of those for free if you're in the right place at the right time, but typically working ones fetch about $1/MHz.
 
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Offline TimNJ

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #34 on: July 26, 2020, 06:48:19 am »
Good information, but why does that power supply I linked to above have  a CE mark on it and say "LED use only?" Also, how could you test it to make sure it is compliant? I'd love to know that. Does complaint mean ripple and etc are in spec?

The standards in question relate to EMC (radio interference) and safety, not functionality. The ripple voltage, for example, could be atrocious, but that wouldn't make it non-compliant from a legal standpoint.

To test it properly, you'd need to take it to an approvals lab where they'd put it in a screened enclosure, connect it to a load (which in this case is an LED lighting strip) and measure the radio emissions from it. It's also tested for its conducted emissions back up the mains cable, immunity to spikes, surges and drop-outs in the mains supply, and immunity to radio interference generated by other nearby equipment.

In terms of safety they'll look at things like electrical isolation between the mains and the low voltage output, the temperature of the case when it's under full load, flammability, current leakage to earth, and whether or not it's correctly marked with voltage and current ratings, type of fuse and so on. A lot of the process is about paperwork.

Got it. I would hope those PSU would at least be safe. A scope could test for voltage and ripple and other undesirable, though, correct? I'm less worried about burning to death than protecting my equipment :)

Just be aware that there is a lot more sketchy stuff on Amazon than you might think. I don’t know the vetting process for items like power supplies, but there are certainly many which have slipped through the cracks. Some may have questionable safety and/or lack relevant safety documentation. Others might be safe but do not comply with mandated efficiency or EMC requirements. As expected , these items tend to be cheap and thus appealing to consumers, but in reality may be ignoring some regulations intended to help the consumer and protect society as a whole. Not to mention, undercutting legitimate manufacturers who ARE abiding by the laws.

By the way, technically power supplies for LED lighting should be IEC61000-3-2 “Class C” compliant for line frequency harmonic current. This is a measure of current drawn by the power supply at harmonics of the line frequency (50/60Hz). Drawing large currents at the harmonics can cause line voltage distortion, which in turn can mess up other systems on the same power distribution network.
 
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Offline DW1961Topic starter

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #35 on: July 26, 2020, 08:33:01 pm »
Good information, but why does that power supply I linked to above have  a CE mark on it and say "LED use only?" Also, how could you test it to make sure it is compliant? I'd love to know that. Does complaint mean ripple and etc are in spec?

The standards in question relate to EMC (radio interference) and safety, not functionality. The ripple voltage, for example, could be atrocious, but that wouldn't make it non-compliant from a legal standpoint.

To test it properly, you'd need to take it to an approvals lab where they'd put it in a screened enclosure, connect it to a load (which in this case is an LED lighting strip) and measure the radio emissions from it. It's also tested for its conducted emissions back up the mains cable, immunity to spikes, surges and drop-outs in the mains supply, and immunity to radio interference generated by other nearby equipment.

In terms of safety they'll look at things like electrical isolation between the mains and the low voltage output, the temperature of the case when it's under full load, flammability, current leakage to earth, and whether or not it's correctly marked with voltage and current ratings, type of fuse and so on. A lot of the process is about paperwork.

Got it. I would hope those PSU would at least be safe. A scope could test for voltage and ripple and other undesirable, though, correct? I'm less worried about burning to death than protecting my equipment :)

Just be aware that there is a lot more sketchy stuff on Amazon than you might think. I don’t know the vetting process for items like power supplies, but there are certainly many which have slipped through the cracks. Some may have questionable safety and/or lack relevant safety documentation. Others might be safe but do not comply with mandated efficiency or EMC requirements. As expected , these items tend to be cheap and thus appealing to consumers, but in reality may be ignoring some regulations intended to help the consumer and protect society as a whole. Not to mention, undercutting legitimate manufacturers who ARE abiding by the laws.

By the way, technically power supplies for LED lighting should be IEC61000-3-2 “Class C” compliant for line frequency harmonic current. This is a measure of current drawn by the power supply at harmonics of the line frequency (50/60Hz). Drawing large currents at the harmonics can cause line voltage distortion, which in turn can mess up other systems on the same power distribution network.

Well, let's hope they test enough of them to keep them relatively in compliance, but I have my doubts too. The only way to tell is to scope them under load. It would be interesting to do.
 

Offline james_s

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #36 on: July 27, 2020, 05:22:25 pm »
I have three DMMs. All capable of doing current test. What could I use for a power source instead of getting a bench supply? I mean, they're like $120.00 bucks on Amazon.

I didn't see this earlier.

I used various salvaged "wall wart" type adapters for years, batteries, power supplies salvaged out of scrapped equipment. Now there are a lot of cheap modules you can get from China to build a bench power supply, just add a surplus laptop charger or other similar PSU and put it in a box and you're good to go, I think Dave did a review on one of those a while back. If you have a decent thrift store around those can be a good place to get power adapters, used to be one down near our cabin that had a whole bin of cast off AC adapters and power cords for 99c each, I got several good ones from there. Those all in one scanner/printer/fax things get junked all the time and often have an adapter that puts out around 32V at several amps.
 

Offline DW1961Topic starter

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #37 on: July 27, 2020, 10:43:25 pm »
I have three DMMs. All capable of doing current test. What could I use for a power source instead of getting a bench supply? I mean, they're like $120.00 bucks on Amazon.

I didn't see this earlier.

I used various salvaged "wall wart" type adapters for years, batteries, power supplies salvaged out of scrapped equipment. Now there are a lot of cheap modules you can get from China to build a bench power supply, just add a surplus laptop charger or other similar PSU and put it in a box and you're good to go, I think Dave did a review on one of those a while back. If you have a decent thrift store around those can be a good place to get power adapters, used to be one down near our cabin that had a whole bin of cast off AC adapters and power cords for 99c each, I got several good ones from there. Those all in one scanner/printer/fax things get junked all the time and often have an adapter that puts out around 32V at several amps.
That's a good idea, but those bench supplies on amazon are like 50-70 bucks. Also, I want t make sure the power is clean. Who knows what the ripple is in those other types of supplies is, for instance? a bench supply would make things so much easier.

On the other hand, if I had a decent scope, I could test the supply under load and see how it performs - lol.
 

Offline cdev

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #38 on: July 27, 2020, 10:48:50 pm »
Good information, but why does that power supply I linked to above have  a CE mark on it and say "LED use only?" Also, how could you test it to make sure it is compliant? I'd love to know that. Does complaint mean ripple and etc are in spec?

The standards in question relate to EMC (radio interference) and safety, not functionality. The ripple voltage, for example, could be atrocious, but that wouldn't make it non-compliant from a legal standpoint.

To test it properly, you'd need to take it to an approvals lab where they'd put it in a screened enclosure, connect it to a load (which in this case is an LED lighting strip) and measure the radio emissions from it. It's also tested for its conducted emissions back up the mains cable, immunity to spikes, surges and drop-outs in the mains supply, and immunity to radio interference generated by other nearby equipment.

In terms of safety they'll look at things like electrical isolation between the mains and the low voltage output, the temperature of the case when it's under full load, flammability, current leakage to earth, and whether or not it's correctly marked with voltage and current ratings, type of fuse and so on. A lot of the process is about paperwork.

Got it. I would hope those PSU would at least be safe. A scope could test for voltage and ripple and other undesirable, though, correct? I'm less worried about burning to death than protecting my equipment :)

Just be aware that there is a lot more sketchy stuff on Amazon than you might think. I don’t know the vetting process for items like power supplies, but there are certainly many which have slipped through the cracks. Some may have questionable safety and/or lack relevant safety documentation. Others might be safe but do not comply with mandated efficiency or EMC requirements. As expected , these items tend to be cheap and thus appealing to consumers, but in reality may be ignoring some regulations intended to help the consumer and protect society as a whole. Not to mention, undercutting legitimate manufacturers who ARE abiding by the laws.

By the way, technically power supplies for LED lighting should be IEC61000-3-2 “Class C” compliant for line frequency harmonic current. This is a measure of current drawn by the power supply at harmonics of the line frequency (50/60Hz). Drawing large currents at the harmonics can cause line voltage distortion, which in turn can mess up other systems on the same power distribution network.

Well, let's hope they test enough of them to keep them relatively in compliance, but I have my doubts too. The only way to tell is to scope them under load. It would be interesting to do.

Some of the designers of the cheap power supplies should go to jail for cutting corners the way they do. I say that because they kill people, usually poor young people, all of the time.
"What the large print giveth, the small print taketh away."
 
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Offline james_s

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Re: How do you tell what "type" of power a DC power supply is?
« Reply #39 on: July 28, 2020, 03:46:18 am »
That's a good idea, but those bench supplies on amazon are like 50-70 bucks. Also, I want t make sure the power is clean. Who knows what the ripple is in those other types of supplies is, for instance? a bench supply would make things so much easier.

On the other hand, if I had a decent scope, I could test the supply under load and see how it performs - lol.

If you have the budget then a proper bench supply is better, I'm just trying to give you options.

Don't forget there are also a lot of good quality used power supplies available from places like ebay. Others may have some specific recommendations.
 
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