Alright, everyone!
I’ve recently fitted a set of 12V LED garden spotlights in the back garden – about 10 of them, each drawing 5W. At the moment, they’re running off an old magnetic low-voltage (MLV) transformer, which gives out 12V AC and has a total rating of 80W.
Now, the snag is I’d really like to add a dimming function to these lights so I can get a softer glow in the evenings. I tried chucking on a leading-edge dimmer I had knocking about, but the lights are dimming really unevenly, sometimes flickering, and the dimmer itself is giving off a slight hum.
I’ve heard that LEDs are usually best with a trailing-edge dimmer, and that with low-voltage systems, there’s a difference between electronic low-voltage (ELV) and magnetic low-voltage (MLV) transformers. My main head-scratchers are:
Can I keep my current MLV transformer, or will I absolutely need to pair it with an MLV-compatible trailing-edge dimmer?
If I need to switch to an electronic low-voltage (ELV) transformer for better dimming, will my existing 12V LED bulbs actually be compatible with an ELV unit? Any recommended ELV transformer models that won’t break the bank?
For outdoor use, does anyone have any pointers for a waterproof universal dimmer? Ideally, a smart one that I can control with my phone.
What are the key things to look out for when changing transformers and dimmers, like cable sizing or ensuring the minimum/maximum loads are matched up?
Fingers crossed some of you seasoned pros can shed some light on this for me and stop me making a hash of it! Cheers for any help!
Too2dBegginer
Low-voltage LED Garden Lighting Upgrade: Will My Existing Transformer Cope?
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You’ve hit a very common snag with LED dimming, and your observations (flickering, hum) are spot on – it’s almost certainly a compatibility issue with your MLV transformer and leading-edge dimmer trying to talk to LEDs.
Here’s the simplified lowdown:
1. MLV Transformers & Dimming LEDs: Not Ideal.
Your current magnetic low-voltage (MLV) transformer combined with a leading-edge dimmer is causing the trouble. MLVs are great for old halogens, but LEDs are different beasts. They prefer a cleaner power supply for smooth dimming. For reliable, flicker-free dimming, you’ll almost certainly need to replace your MLV transformer.
2. The Solution: ELV Transformer + Trailing-Edge Dimmer.
The gold standard for dimming 12V AC LEDs is an electronic low-voltage (ELV) transformer paired with a trailing-edge dimmer. This combo provides a much smoother power delivery, stopping the flicker and hum. Your existing 12V AC LED bulbs should be compatible with an ELV transformer – the key is the transformer and dimmer working together.
3. Outdoor & Smart Dimming:
For outdoor use: You’ll need an IP-rated (waterproof) ELV transformer. Look for brands like Mean Well or those stocked at UK electrical wholesalers. Ensure its wattage is at least 20% more than your total LED load (your 50W needs at least 60W+).
For smart control: The easiest way to get app control is usually to install a smart trailing-edge dimmer indoors (e.g., Lutron, Fibaro, Shelly compatible with your smart home system) that controls the 230V mains supply before it gets to your new outdoor ELV transformer. True outdoor-rated smart dimmers for low-voltage systems are less common.
Key things to double-check:
Ensure your new ELV transformer and trailing-edge dimmer both have their minimum and maximum load requirements met by your 50W (10x5W) total LED wattage. This is crucial for performance and longevity.
To help further, could you confirm a couple of things?
Are your existing LED spotlights definitely 12V AC bulbs, or could they be DC? (Most garden lights are AC, but just to be sure)
What smart home system, if any, are you currently using or planning to use? (e.g., Alexa, Google Home, Apple HomeKit, Zigbee, Z-Wave) This helps narrow down smart dimmer recommendations.
Hope this helps steer you in the right direction and stop the hash!
I’d suggest you first check the make and model of your existing MLV transformer. Sometimes, older transformer brands still have corresponding compatible dimmers on the market. Before you buy anything, you could check the brand’s website to see if they recommend a specific pairing.