Hi all
As I'm taking a short break and doing some DIY. I purchased a LED light, It uses a LED driver and is not dimmable. Well not using a mains dimmer. The issue is that its a big LED strip and is very bright :o
I can see no reason why I cannot PWM the low(ish) voltage once its been through the AD-DC led driver apart from the driver says it is...
180v - 265v AC to 132 - 201 DC It also has 3 wire output labeled N-, +, B-
I can find nothing online about that wiring online and even resorted to Chat gpt via Bing. It just made sh!t up about the B- being the dimming current supply. Following the source link to RS comps the page had ZERO references to B- or Dimmable anything
So I'm looking for enlightenment I want to build a PWM controller to the DC side that will be a small pot controlled mounted in the lighting driver housing.
What is B- and can I PWM it with say a Mfet?
Hi Tim-
I think you may end up fighting an uphill battle by trying to add PWM to that driver. That is a constant-current driver, so it will be trying to maintain a current of 230mA. I suspect that if you add PWM it could cause the constant current circuit to become unstable. Also, you will have to be PWM'ing 200 volts so you'll probably need an isolated driver.
I'm thinking you will be better off to replace the driver with either a dimmable one or a lower wattage one that will supply 200 volts.
Sorry to rain on your parade.
-Rick
Thanks Rick
Any idea what B- is?
Tim
Just a thought and I am probably wrong but could it be 2 seperate negatine outputs with one common positive. Does it look like the LED has 2 segments?
Bob
HI Bob
Yes your spot on. I'm thinking now that if I get a meaty power resistor I can short some of the current through it to reduce the current/voltage going to the leds.
The issue I have is they are way to bright. I need to reduce the lumens
Quote from: TimB on Nov 27, 2023, 08:16 AMThanks Rick
Any idea what B- is?
Tim
Not a clue- but there's a phone number on the driver. Might be worth a shot.
Why not just get a strip of WS2812B RGB LEDs or APA102 RGB LEDs?
They are very inexpensive and can be driven from 4 to 5 volts directly from a microcontroller, and you can make them any colour and any brightness (individually or sections if requied), and they come in very long strips of them that only require a single (WS2812B) or double(APA102) line to them. When fully on, they do draw quite a bit of current when there are a lot of them, but they are very bright. And they are a lot safer than a series of LEDs carrying a high voltage.
Thanks Les
I think swapping out the leds for a COB style would be a good option
Tim
Is it anything like this one Tim? I bought it some years ago at Costco. It's so bloody bright it has given me a tan. I'd love to dim it but haven't had the time or know-how.
Charlie
Quote from: TimB on Nov 27, 2023, 03:09 PMI think swapping out the leds for a COB style would be a good optionTim
Beware of the cheap Chinese COB LEDs. Those COB assemblies do not have any current limiting on each series string. The ones from reputable manufacturers have closely matched chips that share nicely, but the cheap ones tend to be very uneven and will often fail prematurely (voice of experience speaking....).
Hi Tim,
As LED's are current controlled my first thoughts were to search for 'variable current sink' to put control in the low side, but if the original controller is trying to maintain a high constant current then it may not work.
I have used CC IC's to control the high side of back lights but they were only 24 volt circuits.
Hi See_Mos
Hmm yes I think a variable current sink would be a good solution if it can handle say 100ma at 200v. I have a 25 watt 2k2 resistor coming today and will see what happens when I short + to one of the negs. If that works then I will see what can be done with say a 25w pot
Quote from: TimB on Nov 28, 2023, 03:53 PMHi See_Mos
Hmm yes I think a variable current sink would be a good solution if it can handle say 100ma at 200v. I have a 25 watt 2k2 resistor coming today and will see what happens when I short + to one of the negs. If that works then I will see what can be done with say a 25w pot.
Hi Tim
I had a look on line and found 25W opts are available at a reasonable price.
https://www.aliexpress.com/item/32670027322.html?src=google&src=google&albch=shopping&acnt=708-803-3821&slnk=&plac=&mtctp=&albbt=Google_7_shopping&albagn=888888&isSmbAutoCall=false&needSmbHouyi=false&albcp=19373925530&albag=&trgt=&crea=en32670027322&netw=x&device=c&albpg=&albpd=en32670027322&gad_source=1&gclid=CjwKCAiAvJarBhA1EiwAGgZl0JsnL2vrwFMNEswmM5DsVHORHtvvU14YietmPdFfnDCTLfVhC41MyxoCJbsQAvD_BwE&gclsrc=aw.ds&aff_fcid=7f29628d18594caf85f6bbda72901096-1701218688165-09936-UneMJZVf&aff_fsk=UneMJZVf&aff_platform=aaf&sk=UneMJZVf&aff_trace_key=7f29628d18594caf85f6bbda72901096-1701218688165-09936-UneMJZVf&terminal_id=3c29050e5e2c407eb9f2f9eb4ac93f40&afSmartRedirect=y
I must admit this was a surprise to me, even 50W pots are quite cheap.
If the current shunt method works other options could be.
1/ A FET on a heatsink, a small pot and a few components to make a current sink circuit.
2/ A few power resistors maybe heatsink mounted for preset brightness levels switched with FET's, relays or toggle switches.
Have you scoped the fet drive?
Is there galvanic isolation from the mains?
kk
Why not use something that is dimmable by usual means?
In my case because I have bought the thing, struggled on a stepladder to fix it to the ceiling, only then discovering that it's far too bright. If I ever get any time, and trust myself on a stepladder, I'll take it down and poke around inside the control box thingy. It's a beautifully artistic thing.
Charlie
I tried the 25w resistor but it made no difference
I found the LED strip has 3 connections like the rest of the wiring. The LED strip seems to have 2 circuits and the leds are numbered B N B N...
My opinion now is if we keep it (wify is not keen on it) then I will rewire with a standard led strip and mains dimmable controller
Quote from: TimB on Nov 30, 2023, 09:19 AMI tried the 25w resistor but it made no difference
Remember that the resistor will have to go in parallel, not series. If it's in series, the driver will just crank up the voltage to maintain the same current.
I retried the resistor as I realised that one of the channels of leds (they alternate on the same strip) dimmed. So I fitted the other but all it did was dim one channel completely
Searching Aliexpress I found a number of replacement controllers that will match the specs needed. They are not Triac dimmable but they all seem have a remote.
https://www.aliexpress.com/item/1005005066525126.html
I went for that one because the size will fit in the space.
Not got my new driver yet but made a discovery that eluded me before
The light as it turns out has 3 modes. Each Led bank (alternate leds on the strips) is a different colour. Cool white and warm white
If I turn on the light both come on. Off then on again and just the White leds come on. Off and back on and the Warm white leds come on.
If the dimmer does not work then I at least can just chop the drive to the cool white leds and then using a few diodes make sure the warm white is the only one that comes on and use a bigger wattage R to sink some extra m amps to dim the one strip. (The 25watt got a bit to hot for my liking)
The new driver/dimmer arrived from China (wow quick delivery) and after wiring in now works a treat. I have to use the remote control as it does not remember the last setting on switch power down and the remote on/off does not seem to actually turn the Leds 100% off
Overall now its solved
Cheers for the help given
Tim
Well- it's probably too late, but it occurs to me that given the 220 mains on your side of the big pond, and the LED voltage of 132-201V, there is an easy way to make a driver.
The attached schematic takes advantage of the capacitive reactance of a metallized film capacitor. It should be rated 350 volts or higher. It's important that it be a metallized capacitor and NOT an electrolytic, since it will see AC voltage. I'd start with about 1uF. Higher capacitance makes the LEDs brighter. The bridge rectifier obviously converts the AC to DC. R1 limits the inrush into the rectifier and filter capacitor C1. C1's purpose is to eliminate flicker. C1 should be an aluminum electrolytic, maybe 10 to 50uF, with a voltage rating of 350 volts or better. R2 is only needed if there's ever a possibility of the LEDs being disconnected and reconnected while the driver is powered up, since the voltage across C1 will fly up to more than 300 volts in the absence of a load. R1 and R2 are not critical, but you could use 33 ohms 2 watts as a starting point.
Sounds like you've already got this solved. Sorry to be late coming up with a possible solution.
(https://ibb.co/rpQn5hW)
-Rick
Quote from: rick.curl on Dec 11, 2023, 11:51 PMWell- it's probably too late, but it occurs to me that given the 220 mains on your side of the big pond, and the LED voltage of 132-201V, there is an easy way to make a driver.
(https://ibb.co/rpQn5hW)
-Rick
Hi Rick
I believe your solution is technically correct.
My guess is that it may be illegal in the UK, one would need to refer the the regulations.
Voltage spikes with a fast rise time will pass through C2, allowances need to be made for this.
Ken
Hi Tim,
I have one which works similar https://www.tlc-direct.co.uk/Products/GLCPL24CT.html
From the instructions you can set the colour temperature like so, might work for yours. It also has a selector switch which I used.
QuoteColour Temperature Adjustment
The colour temperature may be set by means of a switch on the rear of the luminaire. The
options are:
WW (warm white), CW (cool white), DL (daylight) and SWITCH
The SWITCH option allows the colour temperature to be controlled from an external
wall switch. Switch the luminaire off and on again repeatedly until the desired colour
temperature is achieved. - then switch off and leave off for at least 5 seconds to save the setting
Bob
Thanks Bob
Another feature I did not know was there. Yes it works on the new driver.
Tim