Dimmable LEDS - maybe a "dim" question

[TimmyTee]

Hi all, and thanks in advance for any light you can shed on this topic.

I've been rooting through the stores of our am-dram group and found a box of old halogen floodlights, like this 

My question is whether I can convert them to dimmable LEDs, using something like this: Dimmable 118mm bulb

Well, the answer is obviously yes. But my real question is whether they'd be compatible with a dimmer back, we have a Eurolight LD6230, would it be able to dim them?

The other option would be to use non-dimmable bulbs and set the channel on the dimmer to a straight on/off, that could also be handy.

Lastly, apologies for the bad puns. Shed some light, dim question.... As I said, am-dram.

[Robin D]

I would expect them to work, but suggest as always get one and try it. Make sure there is no preheat set on the dimmer. Expect a fairly sharp snap to off at the bottom end and you may have to play with the dimmer curve to get it to behave as though it were halogen. 

You may also find that some manufacturers work well and others don't. It's trial and error. Buy one and then buy plenty of the one that works best so you have a few spares. 

[sandall]

Maybe not a problem, but 8OW equivalent (possibly nearer 50W in practice) isn't going to be very bright compared to the original 500W K/1 lamp

[TimmyTee]

Trial and error is my usual MO. If it doesn't trip or go up in smoke...

The only trouble is that we're a "homeless" company and I have no way of hooking the dimmer pack up to a 3-phase supply. I suppose I could wire it up to single phase and try it at home.

[TimmyTee]

3 minutes ago, sandall said:

Maybe not a problem, but 8OW equivalent (possibly nearer 50W in practice) isn't going to be very bright compared to the original 500W K/1 lamp

That's a good point, but since we've got at least 10 of them and they weigh next-to-nothing, I'm sure they'll come in handy.

[Tomo]

They'll never dim 'nicely'. Mains dimmable LED doesn't dim to zero, and on those dimmers you'll be lucky to get below 20%.

SCR/Triac dimmers like the one linked have relatively high minimum loads - 40-50W of resistive (tungsten) is a common minimum.
Mains LED lamps like the ones linked will tend to flicker, flash, or never fully turn off at all. Adding more in parallel can make it better - or worse.

I'd suggest fitting non-dimmable LED retrofits and using them as working light.

[richardash1981]

In case you didn't know, CPC in the UK still have stock of the original halogen lamps if you want to stock up on bulbs to make them usable in the original manner for a while longer.

[sunray]

I have tried the Philips pro core 60W in both cool and warm and ended up returning to 300W as house light uplighters as the LEDs don't bounce off the ceiling tiles

Edited August 24, 2022 by sunray

[sunray]

1 hour ago, Tomo said:

They'll never dim 'nicely'. Mains dimmable LED doesn't dim to zero, and on those dimmers you'll be lucky to get below 20%.

SCR/Triac dimmers like the one linked have relatively high minimum loads - 40-50W of resistive (tungsten) is a common minimum.

I've witnessed 500W fresnels etc in a 'back room' as the load on dimmers being used for LED on a number of occasions

[adam2]

LED lamps sold as dimmable should dim on a theatre lighting dimmer, at least to an extent, but do not expect "nice" dimming. You may need to add a tungsten load lamp if the dimmer is to work properly. 60 watts is generally enough. Use of a 500 watt lantern sounds very wasteful of electricity and lamp life.

A three phase dimmer can be used from a single phase d0m3stic supply for low power tests.

[TimmyTee]

All good advice, thanks folks. 

I'm going to drag the dimmer home tomorrow and have a play, wired to single phase.

[alistermorton]

We tried some of those LED replacement lamps in our nocturnes. They were lamentably dim at full and didn't dim at all well on our strand dimmers.  There's a reason linear halogen is exempt from the purge. 

Edited August 24, 2022 by alistermorton

[sunray]

3 hours ago, adam2 said:

You may need to add a tungsten load lamp if the dimmer is to work properly. 60 watts is generally enough. Use of a 500 watt lantern sounds very wasteful of electricity and lamp life.

 

Yes I agree 500W is wasteful but there are usually plenty of them around and how many lighting guys would think about energy waste while rigging?

[adam2]

I suspect that electricity consumption will be taken more seriously than in the past. 60 pence a unit or more is now the going rate and it may go higher still.

And I can remember the good old days of "a penny a unit and the more you want the better" and that was an OLD penny a unit. Gas was cheaper, and when I was but a nipper, there were still coin meters for gas that took pennies.

[Stuart91]

On 8/25/2022 at 4:10 AM, sunray said:

Yes I agree 500W is wasteful but there are usually plenty of them around and how many lighting guys would think about energy waste while rigging?

One factor is how long they stay on for. 

I've still got a collection of Molefay-style blinders, 650w per lamp. Often these days they are the only incandescent lanterns at the show. However all they are used for is brief flashes at the audience, maybe on for a brief chorus when a sing-a-long is called for. So even though the instantaneous consumption is very high, the kilowatt-hours used is relatively low. 

Using incandescents for front wash, where they're on for most of the show, is a very different and much more expensive proposition.