We have a house with an outdoor staircase lit by warm white LED strip lights. However, the lights are "too bright" and we want to lower the intensity of the LED lights. On another loop of the garden lights, the same LED strip lights are lower in intensity because there are more LED lights on the same loop. So, I was wondering what resistor (or other device) would be the smartest to use? A dimmer normally works with 110 V but that is not possible here to use. It has to be something on the low voltage loop so therefore I was thinking adding a resistor or similar to that specific loop. The loop it is currently on is a 5 V loop with 8 LED lights pulling 6 W each (=48 W). Anyone with experience/suggestions?
Electronic – How best to lower LED garden light intensity
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Related Solutions
Your LED bulbs are most likely fitted with a wide-range power supply, operating from 100-240 Vac. Hence, when the voltage dropped, they were still within their operating limits and your LED bulbs were as bright as before.
Side note: You'd be surprised how many bulbs marked 220-240 Vac can actually operate down to 100 Vac or less. The nameplate numbers only tell you where it can operate, not where it can't.
Figure 1. The CIE colourspace with a "best-fit" line running through the whites.
To do what you want would require some good fortune with availability of the right LEDs. To be able to adjust along a best-fit spectrum of whites requires that you have two light sources with colours on the outer ends of the line overlaid on the graphic of Figure 1. Colour control in this case would be fairly simple: blend between blue only to gold only.
If the colours don't line up as desired then you would need at least three colours.
Figure 2. With three colours (located at the points of the triangle) any colour within the triangle can be generated.
In this case control becomes a little more complicated but could still be done without resort to a micro-controller.
Figure 3. A green-blue pair and a green-red pair could generate the two colours at the ends of the grey line.
If a green-blue set of lights is adjusted to generate the blue at the left end of the grey line and a green-red pair is adjusted to provide the hue at the right end of the line then, by varying the relative intensity of the pairs we could travel in a straight line through daylight, cool white and warm white.
Update
simulate this circuit – Schematic created using CircuitLab
Figure 4. A very simple 0 - 10 V dimmer control.
How it works:
- This control is designed to work with 0 - 10 V LED controllers.
- It uses two 2-gang linear potentiometers (pots).
- R1 controls the intensity. As the potentiometer is turned from minimum to maximum the wipers' voltage will increase from 0 to 10 V.
- R2 controls the temperature. Note that the potentiometers' inputs and grounds are reversed. When turned all the way to the left the cool control will get the full value of the intensity setting while the warm control will be grounded and get zero volts. When turned all the way to the right the situation will be reversed.
- With R2 in the centre position both lights will be at 50% intensity. This is intended design to maintain intensity across the range of the temperature control pot.
- The 1 kΩ and 10 kΩ values are chosen so that R2 doesn't load R1 too much (as this would distort the desired linear adjustment.
Figure 5. The potentiometer connections on the PWM controller are not grounded.
Unfortunately your Amazon controller is not suitable for this scheme as the pots have neither end (points 1 and 3) grounded (to 4) and so must not be using a control voltage as required.
Many LED controllers are available with 0 - 10 V control inputs. While it may not suit your application, my article Dimmable mains PSU control explains some of the control features.
Best Answer
The best and most economical way is to reduce the voltage of the supply with the small orange screw near the terminals. Outdoor hermetically sealed supply don't have this adjustable screw (potentiometer). In this case replacing the supply may be necessary. It can be cheaper or not more expensive than buying a PWM dimmer. PWM dimmer consume more electricity but are better fit for accessible, user friendly, regularly adjustment. For a one time adjustment, setting a lower voltage is better and more climate friendly (LOL). The change in voltage has to be of the order of 10%. If you replace the supply by a supply with 30% less voltage, it will be too much. You can reduce voltage safely. But you can't increase it.