techincal knowledge needed

[RichardMoore]

Hi am an electrician with the following dilemma. I've installed 9 dimmable led's on a led dimmer but the minimum load of the dimmer is 60 watts. The lamps are 4.5 watts and only have a total load of 40.5watts When I dim them down they do so far then they begin to flicker. But when i install a standard 50watt lamp the don't.my question if I can explain is. If I was to install a resistor at the EOL of the correct size to increase the current thus the load would increase to a significant size to replace the standard lamp and correcting the problem I have also any advice on resistor sizes that may work thanks for any input much appreciated

 

[Marvo]

If you add a resistor to increase the load current then it's going to be a complete waste of power plus it's going to get pretty damn hot.

Just replace the dimmer with a more appropriate type or leave one of the lamps as a halogen if you must but again this is a waste of power.

 

[SPARTYKUS]

:grinningelf:And as we know from the Pirelli advert, power is nothing without control

 

[RichardMoore]

Isn't a standard lamp of 50watts a resistive load. I could change the dimmer understood but am more interested if a resistor can work???

 

[Marvo]

It can work in theory but in practice it's not an option. A resistor is a small component and you're wanting it to dissipate close to 50watts of heat. Put it this way, a halogen spotlight is maybe 5% efficient at producing light so it's dissipating 47.5 watts of heat and they reach temperatures of 2 or 3 hundred degrees Celsius. Depending on the application not only are you wasting power by creating heat but you could be wasting even more power by increasing the air conditioning load if it's a commercial premises.

 

[telectrix]

as above. the only sensible option is to fit the correct dimmer. adding a resistive load is like buying a car that's good on mpg then driving with the handbrake on.

 

[monkeyelectric]

Try getting a different dimmer suitable for the load!

 

[i=p/u]

I found that with LEDs , dimmed ok to start with then flickered, have to say it was offered with lights but didn't like it.. So haven't fitted one since.

 

[Braiz]

Hey have you tried looking at the varilight v-pro range they have 10w minimum load

 

[ackbarthestar]

Isn't a standard lamp of 50watts a resistive load. I could change the dimmer understood but am more interested if a resistor can work???

Where exactly would you mount this resistor? Its going to be rated at 50W, be ceramic covered wire wound and be around 50mm long with possibly a heat sink . It will get hot particularly in a small confined space!

A standard leading edge power controlled adjustable switch (Traic/Thyristor) is not suitable for switching LEDs. You will require a slightly different type which triggers the control gate on the switching device, usually the trailing edge of the supply waveform. As the LEDs need a DC supply there has to be rectification. It appears that the modern approach is to modulate a pulse across the LED at somewhere in the region of 100 - 400Hz.

However, you should be able to run 9 5W LEDs with a 500W dimmer.

 

[sledgehammer]

If it's only at the bottom end, what about adjustment to not allow to dim down so far. I've seen a couple of methods of this being either a pot on the dimmer or a physical restriction like a ring or stop to limit rotation. Best dimming results for led always as far as I've personally seen are to use 0-10 and then even better 0-10 using Lurton gear.

 

[tazz]

Trailing edge dimmers are designed for dimmerble led lighting such as gu10 etc, IQ and silent are marketing this type through TLC etc, intelligent trailing edge dimmers with minimum load of 2.5w

 

[jimjimjim]

I'd fit a low wattage dimmer like the v-pro but Danlers do a product called Reslode which would do what you're asking.

 

[Marvo]

The Reload supposedly emulates an extra load of only 10Watts plus they're prone to damage during IR testing with a Mega tester. I'd avoid them like the plague to be honest.

 

[D Skelton]

A trailing edge low wattage dimmer is what you need. Failing that, a suitably rated capacitor would do the trick, I often have to use caps when fitting grafik eyes.