Why are my LEDs so dim?

[Cyril Eaton]

I have 5 x 5W LEDs connected to a 12V transformer powering the lights in my kitchen.
The transformer is described as 20 - 60W so at 25W I'm above the minimum load requirement.
The lamps are described as 10 - 30V 5W LEDs so with the transformer output at a stated 11.6V I'm within the tolerances of the lights.
I've checked the transformer output and it is actually 11.8V
They work OK, but these are supposed to be the equivalent of 50W Lamps (500 lumens) yet they are not that bright.
I also have a separate 35W Mains powered Halogen lighting a step area and it is far brighter, yet it is only rated at 320 lumens.
I've checked all of the wiring to ensure the connections are sound.
Any ideas why these LEDs are so dim?
I know we are meant to be thinking of the environment and using LEDs, but I feel like cutting my losses, ditching the LEDs and reverting to mains powered Halogens?

 

[pc1966]

What make/model of LED?

Are they for an AC supply (i.e. replacement for halogens) or intended for use with a 12V DC supply (i.e. just for safety low voltage applications)?

What is the "transformer" type, simple AC output or a DC LED driver?

Are they of the same style as the halogen (e.g. both with reflector, or both omnidirectional)

While the "equivalent lumens" is often optimistic to the point if lying, a 5W LED light ought to be equivalent to at least a 35W halogen bulb.

 

[plugsandsparks]

As above you need to double check the LEDS are constant voltage type or constant current type, then that the driver is compatible in voltage , current and wattage.

If you post answers to the above question, i am sure someone can help

regards

P&S

 

[HappyHippyDad]

I have 5 x 5W LEDs connected to a 12V transformer powering the lights in my kitchen.
The transformer is described as 20 - 60W so at 25W I'm above the minimum load requirement.
The lamps are described as 10 - 30V 5W LEDs so with the transformer output at a stated 11.6V I'm within the tolerances of the lights.
I've checked the transformer output and it is actually 11.8V
They work OK, but these are supposed to be the equivalent of 50W Lamps (500 lumens) yet they are not that bright.
I also have a separate 35W Mains powered Halogen lighting a step area and it is far brighter, yet it is only rated at 320 lumens.
I've checked all of the wiring to ensure the connections are sound.
Any ideas why these LEDs are so dim?
I know we are meant to be thinking of the environment and using LEDs, but I feel like cutting my losses, ditching the LEDs and reverting to mains powered Halogens?

Did you buy the LED's from ebay/amazon or from a reputable dealer? There are a lot of very cheap poor quality LED bulbs around that do not live up to the specification that is stated on the advert.

Also, they are not designed to be used with a transformer, they are designed to be used with an LED driver. Perhaps buy one LED driver and see if this makes a difference, then buy more if it does. However, the best option would be to change the ones you have to mains voltage and use GU10 LED's (not from amazon/ebay), screwfix sell them at good value and they live up to their spec.

I also found once that when I installed a dimmer switch on one set of lights, it made another set (on a normal plate switch go dimmer)!!

 

[telectrix]

sounds like the LEDs want a constant current driver.

 

[Taylortwocities]

sounds like the LEDs want a constant current driver.

If so, wouldn’t they need to be rewired so they are in series, not in parallel?

another request for the spec of the LED lamps.

 

[DPG]

+1 for cheap lamps and made-up wattage figures.

 

[Cyril Eaton]

Thanks, everyone. I'm comparing costs of changing to mains powered from Low Voltage. If I'm going to rewire I'd sooner take that approach. Seems I missed the bit about Constant Voltage/Current when going down the Low Voltage route. I never buy cheap for these things and will take up the claim about lumens with the Supplier.

 

[Taylortwocities]

Please tell us the lamps you are having problems with. We may have more/better/specific advice.

 

[brianmoooore]

It's a long shot, but have you checked the voltage at the lamps? If the Tx is some distance away, and the supply cable is thin, then it could be below the minimum voltage at the lamps.

 

[HappyHippyDad]

It's a long shot, but have you checked the voltage at the lamps? If the Tx is some distance away, and the supply cable is thin, then it could be below the minimum voltage at the lamps.

Most LED's can work at pretty low voltages. Possible, but I think it may be more of an ultra long shot ?

 

[Lucien Nunes]

We need to know what the 'transformer' is. An electronic 'transformer' designed for halogen lamps is not simply a transformer, they are often high-frequency AC output and only suitable for halogens. The fact that it is rated at 20-60W 11.6V makes me think it is of this type. 11.6V is used to slightly under-run the halogens to make them last longer. I would therefore not expect this unit to work with LEDs, and it might damage them.

The LEDs sound like they have active electronics within if they are capable of operating on a wide range of voltages. Nonetheless they would then be described as 'constant-voltage' and hence would require a constant-voltage DC power supply unit or constant-voltage LED driver within their specified voltage range. The LEDs do not seem to be constant-current otherwise the current would be stated.

 

[marconi]

I suspect your MR16 10-30V led lamps are direct current only and will require a suitable power supply driver to produce it:

MR16 LED Bulbs 12/24v - litecone.co.uk - https://www.litecone.co.uk/mr16-led-bulbs-12v-24v.html

and:

24v LED Drivers - litecone.co.uk - https://www.litecone.co.uk/24v-led-drivers.html

The lamps contain a bridge rectifier circuit so that the pins are not polarity sensitive ie: it does not matter which way around you plug the two pins into the lamp holder.

Your current ex-halogen lamp transformer does not provide the correct constant voltage waveform even though the lamp's internal bridge rectifier converts the transformer's alternating output to a uni-directional voltage waveform - it is not constant. For reasons I will not go into now the lamp's internal voltage regulator (so it can operate over 10-30V range) only works when the input is constant as from a battery.

A trial if you fancy: Connect a halogen and then one of your LED lamps across your car's battery- I expect them to be of the same brightness. Be careful not to short the wires!!! Please tell us what you find.