Bedroom Low Level Lighting Issue

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A while back you may remember I discussed the above.

I have fitted three Click MM1000CW: https://www.electrical2go.co.uk/click-new-media-240v-1w-led-euromod-cool-white-mm1000cw.html

They fit in a 1G box on a euro mod plate.

These sadly are not dimmable and are too bright for Mrs Secure.

I guess if they are not dimmable, they would not take kindly to resistors in circuit.

I have had a look at alternatives that fit a 1G box and options are limited.

I have found this: https://www.downlightsdirect.co.uk/collingwood-mc015s-2w-mini-cube-wall-kit-240v.html, which I don't think is dimmable either and is twice the wattage.

The other is this Collingwood one recommended in a previous thread, but I think it is obsolete now:
https://www.diynot.com/diy/threads/flush-mount-led-luminaires-that-fit-a-1g-metal-box.463634/page-3
 
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These sadly are not dimmable and are too bright for Mrs Secure. .... I guess if they are not dimmable, they would not take kindly to resistors in circuit.
I'm not sure what you mean by 'would not take kindly, but I certainly can't see a series resistor doing any harm to the LED module.

If the resistor were high enough in value, the light output would inevitably fall to zero (or imperceptible) - so the only question is whether there is a reasonably gradual diminution of light output as the resistor value increases (in which case you could select the resistor value that gave you the desired result) or whether there is a threshold value (of resistor) beyond which light output would suddenly cease (or flickering suddenly start).

Given the modest price, if it were me, I think I would probably 'suck it and see' (i.e. do some experiments!).

Kind Regards, John
 
Electronics not really my forte.
What values would you try? Ideally, I want to reduce light output by half (assuming no flickering).
 
Electronics not really my forte. What values would you try? Ideally, I want to reduce light output by half (assuming no flickering).
Not a simple question, since goodness knows what actually goes on within the module (it may be nothing more than a capacitor and bridge rectifier, but could be something closer to an SMPSU) - the relationship (if any) between voltage applied to the module and current through the LED, and the relationship between light output and LED current (assuming one could successfully vary it) would be unknown quantities.

However, as a starting point (and without troubling you with the maths), I will consider the case of the module having simple capacitive current control. If the module draws 1W at 240V (hence a current of about 4.2mA, all of which would go through the LED element in this simple case), one could, if I've got my sums right, approximately halve that current (to about 2.1mA) by putting a resistor of about 100kΩ in series with the module. About 0.44W would be dissipated in that resistor, so you would want one rated at a minimum of 0.5W (probably ≥1W, if you didn't want it to get too hot).

We obviously don't know whether that will work at all with your module (the light may go completely out, or might flicker), and I haven't a clue whether halving the current would do anything like half the light output - but if you used that as a starting point, you might at least get a feel as to whether there was any future in the approach. Even if the principle works, you might find that you have to change the resistor value a lot (in one direction or the other) to get the result you want.

The simpler/'cruder' the module (e.g. just a capacitor and rectifier), the more likely the approach is to work

Kind Regards, John
 
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You would be better off opening the module first and determining the circuit topology. Don't just add a series capacitor.
 
You would be better off opening the module first and determining the circuit topology. Don't just add a series capacitor.
That's certainly what I would do - and I haven't even suggested a series capacitor (which would be the most logical {no heat generation} if 'just a capacitor' is what it already had) since secure asked about a resistor. However, given that he said that 'electronics was not his forte', I was hesitant to suggest that he opened it up - but I suppose that, if he can do so fairly easily (and non-destructively), some photos of what he finds might enable us to make some sort of assessment of what is going on in there.

Secure: IF the module does have just a series capacitor (plus a rectifier) (and possibly even if it has some different electronics) then, rather than the resistor, you could probably try a capacitor (rated at a minimum of 240V AC) of, say, about 0.05 μF (50 nF).

As I said at the start, I can't see that that trying either a series resistor or series capacitor could do any harm to the module.

Kind Regards, John
 
Not a bad idea, thanks.
Was thinking of "wrapping" them in a white film, but that may be better.
 
IMG_20180711_150615.jpg
IMG_20180711_150944.jpg
 
BTW, you probably don't need to remove the existing capacitor or do any soldering. A series 22/27/33 nF with one of the incoming live terminals will do the job.
 
BTW, you probably don't need to remove the existing capacitor or do any soldering. A series 22/27/33 nF with one of the incoming live terminals will do the job.
Indeed. I suppose we are all guessing how much light reduction secure wants (and, indeed, how much light reduction will result from given reductions in LED element current) - I was clearly aiming for a bit more light when I suggested 'about 50 nF' (which could obviously be 47 or 56 nF)! In the final analysis, I suppose that it really has to be down to secure to determine, by experiment, what produces his desired result.

Kind Regards, John
 
I recently had to add a control to one of our pieces of test equipment, to adjust the led indicator levels individually in the field. As various sources in the past have indicated, the results is by no means linear. Typically I have had to adjust to much lower inputs than the brightness would have indicated. My control method was pwm so in the present case the results may be different, but initially I'd lean towards the smaller values myself.
 

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