Re LED transformers for hard-work

[hard-work]

Bernard, Winston, etc, So what is the appropriate transformer? This:
https://www.tlc-direct.co.uk/Produc...Kr1wEsKRIh3B5T2RDNfwsqB8kVJTM_8YaAoJaEALw_wcB

 

[bernardgreen]

Output 11.5 volts 4.3A eff. Max

Your LED strips require a DC supply hence that "transformr" is NOT suitable

 

[ban-all-sheds]

John, the two transformers were for two different LED strips in one room, but one could be used. But, the transformer would be unswitched and always on. The two LED strips can have their own transformers and be switched, but and earth wire in a T&E cable would need to be used on the 12v side.

As John said - a diagram to explain what you're planning would be invaluable.

But maybe you should be using a different sort of cable for the 12V wiring?

 

[Risteard]

But maybe you should be using a different sort of cable for the 12V wiring?

There's no maybe about it. Using the uninsulated (and if not 1mm^2 then also smaller) cpc core of T&E for another purpose is ample proof that it is not the correct cable for the application.

 

[bernardgreen]

For what it is worth......

Portable radio in a kitchen did not seem to work well when the LED strip lights were on.

There was 2 metres of flat twin flex between the LED power supply ( 12 v DC eff) and the LED strip it was feeding ( 3 metres of 3 LED + resistor groups ).

Replacing the flat twin flex with twisted pair flex allowed the portable radio to work when the LED strip lights were lit.

 

[ban-all-sheds]

It wasn't, actually....

 

[ban-all-sheds]

The transformers are not in the the rooms the LEDs are in.

But that has no bearing on how they are switched.

 

[winston1]

Bernard, Winston, etc, So what is the appropriate transformer? This:
https://www.tlc-direct.co.uk/Produc...Kr1wEsKRIh3B5T2RDNfwsqB8kVJTM_8YaAoJaEALw_wcB

There is no appropriate transformer as LED strips require
DC and transformers give out AC, as I have said several times. That also includes switch mode power supplies as above incorrectly labelled "electronic transformer".

The appropriate driver is a 12 volt DC power supply.

 

[ericmark]

There is no appropriate transformer as LED strips require
DC and transformers give out AC, as I have said several times. That also includes switch mode power supplies as above incorrectly labelled "electronic transformer".

The appropriate driver is a 12 volt DC power supply.

I would agree most likely not suitable as most likely needs a DC supply, or should it be called a polarised supply? Since the current likely does alternate between zero and maximum can't really say it's not alternating current, if not smoothed it will still cause imbalance it wrong feeders are used in the same way as true AC. Plus we are only guessing the strip lights actually need a DC supply, when we first started talking about MR16 replacements we also assumed the 12 volt type were DC, however it was found many were marked 50 Hz.

I think it very likely that the LED's are in groups of 3 plus a resistor as a simple driver between two feeder wires, however we have not seen any spec for the strip so we are just assuming. I looked at a few adverts this one was interesting this is a part copy of the data sheet.

• Power: 70 W
• Voltage: 12V DC
• Frequency: 50-60 Hz
• Lumens: 1680 lm/m

I am sure it is DC but it also states 50 - 60 Hz which if not smoothed and using a transformer and simple rectifier it could be still 50 or 60 Hz depending if used in Europe or USA. The other thing stated in nearly every add is "for decoration" at 24 lumen per watt they could not be sold for lighting. The last point to make is dimmers and colour changing modules are placed between the power supply output and the strip, so it would seem it is common to switch the extra low voltage supply, I know with inverters to drive motors there is a warning not to put any switches in the output, and so it does go against the grain, but it seems for lighting it is permitted. At 12 V 70 W however that is around 6A and if DC and there is a if there as it could be polarised AC, then the switch must be designed for DC.

It does seem an odd thread being split like this, think it would have been better kept to one. I am assuming this is just between electricians?

So one other point if using a pulsed supply at around 47 kHz even if polarised then the feeder could be critical as to length just like with an AC supply, however the problem is a typical advert does not tell us what we are buying, find a well known make and you may find a data sheet, however in the main you would need to buy and then feed the output into an oscilloscope to find out what you really have, I suppose a cheap method feed a transformer if no output then input is DC if there is an output then input is AC but you need to buy the power supply first, one really has no idea what you are buying.

Has any one actually tested one, I am unlikely to buy one just to test it, so I will never know.

 

[bernardgreen]

It does seem an odd thread being split like this, think it would have been better kept to one. I am assuming this is just between electricians?

A MOD decided that genuine concerns about SMPS devices should be treated as a joke and some contributorrs were barred from posting in the thread.

 

[winston1]

I think it very likely that the LED's are in groups of 3 plus a resistor as a simple driver between two feeder wires, however we have not seen any spec for the strip so we are just assuming. I looked at a few adverts this one was interesting this is a part copy of the data sheet.

• Power: 70 W
• Voltage: 12V DC
• Frequency: 50-60 Hz
• Lumens: 1680 lm/m

I am sure it is DC but it also states 50 - 60 Hz which if not smoothed and using a transformer and simple rectifier it could be still 50 or 60 Hz depending if used in Europe or USA.

The person who wrote that advert was clearly an idiot. Those 5050 strips are always DC. Possibly the 50/60Hz was referring to the power supply input, but with electrics one must not assume.

Interesting about RFI from LED power supplies. I have never used an official LED power supply so I have no idea if they have a pulsating output. With the LED strips I fitted in a wardrobe I recycled old 12 volt DC power supplies from the likes of Freeview boxes. These have a pure DC output so they must have proper filtering and smoothing, and certainly did not produce RFI.
It could well be that official LED power supplies are made "down to a price" and omit filtering components.

 

[ban-all-sheds]

A MOD decided that genuine concerns about SMPS devices should be treated as a joke and some contributorrs were barred from posting in the thread.

No, he decided that we did not need another example of the utter rubbish you keep writing on that issue.

 

[bernardgreen]

we did not need another example of the utter rubbish you keep writing on that issue.

Do some research and maybe you will be less ignorant about the hazards that cheap SMPS devices can create and the hazards that good quality SMPS devices can create when not used correctly ( such as long leads on the output ).

Or provide some evidence of your qualifications to pass judgement on matters relating to radio communications and the resolution of problems affecting communications. Mine is 12 years working as a design and development engineer in a company that specialised in high integrity radio communication systems and equipment. Among the customers were several emergency services in the UK and abroad.

There is not much in the public domain about incidents where radio communications have been compromised by spurious radio frequency radiation from SMPS devices

Some starting points for your research.....

http://www.conformance.co.uk/adirectives/doku.php?id=emc

https://www.ukqrm.org.uk/smps.php

https://www.ukqrm.org.uk/your-story.php

http://ieeexplore.ieee.org/document/7893115/

 

[winston1]

All very interesting. I wonder why Ofcom are so reluctant to do anything about interference from PLT devices.

 

[ban-all-sheds]

The same old utter rubbish that he has written countless times before.

Bernard - it really does not make a scrap of difference how often you repeat it, until you show how it is the NAMING of the devices which either causes the problems or prevents the makers and/or sellers of them from warning of the problems, then it will remain rubbish in the context in which you write it.

You, of course, will now ignore any request to show how the name is relevant, just as you have done countless times before, and no doubt we can all look forward to you writing your utter rubbish again, in the future.