How to dim an LED downlight on the low voltage side?

Sorry for question title wasnt sure how to word this. I have an offgrid office and have put in an LED downlight (from Bunnings), this has a transformer that plugs directly into an inverter that runs off a 12v Battery. Is there some sort of rotary dimmer that I can use AFTER the transformer? The usual ones sold at Bunnings etc vary the voltage to the transformer (I think), but I want to just simply plug the transformer straight into the inverter.

 

my understanding is if you change resistance on the negative line between the two, it'll allow you to dim it. You may be able to find a dial that lets you alter resistance on the fly.

 

What does it say on the transformer output 12v? how many amps? and I'm assuming the 'transformer' is actually stepping down the 240vac to a DC level to run the LED's
throwing a resistor into the DC side will dim the light but waste power, you need a PWM controller
Search ebay or ali express for "pwm led dimmer" or "pwm motor controller"just make sure it can handle the current

Much more efficient to run a LED strip direct from your battery/s no waste through the inverter

 

Hi, the transformer says 23-28v and 260 mA
Yes good point on the 12v option, this is using 2 transormers I guess, the inverter then the LED transformer, very inefficient huh. I should have thought of that earlier, but there are only a couple of lights. 12v wouldnt be enough to drive the light I have now Im guessing.

So I can use a PWM on the DC side?

EDIT:
So something like this would work?
Ebay PWM dimmer

 

Should work but I would suggest getting a module specifically for LED's as the freq will be higher to avoid flicker

like this https://linearlux.com.au/product/ll-con-rd5/ or this https://www.ebay.com.au/itm/335202755755 which is in a box already just hook up the wires

 

Awesome, thanks so much for taking the time to send me in the right direction

 

Flicker may be an annoying side effect

https://www.google.com/search?q=led+flicker+on+dimmer

 

Yes. all my LED strips are dimmed with PWM. I use the various dimmers from p5.hu - though was in the automation industry, and I'd suggest to just go for something off Aliexpress - or, there are likely devices such as those made by Shelly(?) that are not particularly expensive and also allow for app control, along with a physical button.

Usually these days, dimming is with a single button - tap for on or off, and press and hold for dim/raise (the function alternates). Mechanical dials tend to have short lives.

Z...

 

Ahh well it didnt work out, I bought this off Ebay:
https://www.ebay.com.au/itm/234770908984
It basically sort of flashes the LED on and off a bit, it remains on more the less resistance you ask for and at about 3/4 its fully on, no dimming really.
That dimmer is a 12-24v device, my transformer says 23-38v, it also calls itself "dimmable" (via 240v options it would mean).
Meter on it shows 38v at full input and as I turn the dial it does go down in voltage to about 35 or so where the light starts turning off.
Any thoughts on a different dimmer that might work? I could look at the 240v option but I liked the idea of dimming via the low voltage side since this is all just in the top of a cupboard, no switch boxes etc to put a 240v dial into.

 

You wont see any change in voltage from the LED dimmer output its controlling the duty cycle

https://www.google.com/search?q=pwm+duty+cycle

Can you link the bunnings light, pic of the transformer, a pencil sketch of how you have it wired up, the dimmable 240v idea is the same but its cutting off parts of the sine wave before it gets to the TX

There's something going on with the light +Transformer package that it may not like.

End of the day it maybe less frustrating to buy a LED strip on a roll+ dimmer package from Ali or Ebay if the inverter you're using is in the same room and you have access to the 12VDC run it off that

 

The fact that it lists a 5V spread in the output voltage and a very specific current rating makes me think this is probably a constant current supply, trying to add resistance or PWM on the output side is unlikely to have the desired results. Either use an AC side dimmer, or get some LED strips that are designed to run off 12V.

 

A variable resistor would allow you to dim the light as much as you want, yet would also not use a pwm feature which would cause flickering.


Note: it does not matter whether it is before or after the light, it will have the same effect. But for safety reasons, make it on the 12v side of the transformer please.

Now, I can't advise, on components but would need specs on the rest of the setup.

Send a picture of the sticker on the light and transformer ect:

 

A variable resistor won't work with a constant current power supply, the PSU would just increase the voltage to compensate. You could keep increasing the resistance until it reached the maximum voltage the supply is capable of, at which point the behaviour would depend on the design of the power supply, maybe it starts dimming, or maybe it decides that it's out of spec and completely shuts down.

 

Heres a pic of the transformer and how I have it hooked up. I was checking the voltage on the output of the dimmer. I like the nice black downlight, didnt want to use LED strips. If there is a dimmer that can do this job Id buy it but this one didnt work unfortunately.

 

Transformers are what old style downlights used to use, there are new led bulbs that are suitable for retrofitting into a transformer based system. To over simplify a bit, transformers are voltage based while LEDs are current based, LEDs that are designed to work with plain old transformers have the smarts in the bulb.

What you have there is not a transformer, it is an LED driver, the smarts for controlling how much power goes into the LED are in the driver. When you try to mess with stuff between the driver and the bulb you are making it no longer behave like a simple LED. The driver will try to compensate but the results will be unpredictable at best.

The driver specifically says it supports dimming on the AC side, so the way to make it work is to use that.

 

Aha, ok thanks, I might just make a small box up then and put the proper dimmer on that and wire it on the AC side.
I guess I just like the idea of doing it on the low volatage side for safety and simplicty but not possible with this "box of tricks" huh, thanks.

 

Get a sparky to wire your dimmer on the AC side.

 

All done, bought a little rotary dimmer from Bunnings and wired it in, works as intended of course. Ive leaned a little about LED drivers though so thanks for the info all who gave it.