LED lighting PCB - want to add a second LED driver module for a dim mode - Page 1
Forum section: electronics / projects

author: badrequest400
author_rank: Contributor
timestamp: January 09, 2024, 06:53:25 pm
content: I have this LED light which has its own built-in power supply on the PCB. However, I also want to have the option to run it at lower power using a different modified (72-160 V) LED driver module (that way I can use a switch to choose between high and low brightness).The problem is: I don't understand the arrangement of the LEDs.The chips appear to each contain 6 LEDs giving each chip a forward voltage of ~18 V. They're arranged in two groups of 4P6S so each group must take about 108 V. The groups are not connected to each other in parallel or series.The positive side of one group of LEDs is connected to the negative leg on the electrolytic and the negative side of the other group is connected to the positive leg.The SOP8 chips are labelled MLS3535B but I can't find any information on them. They're not like other high voltage LED driver chips I've seen like the BP2861. The legs on one side of the chips are all shorted together, for example. Changing the values of R1 and R2 changes the current passing through the LEDs and those resistors are connected to two legs of the SOP8 chip.Are there places I can attach the outputs of my other LED driver so it lights both groups of LEDs. Of course only one driving circuit will be powered at any one time.

author: thm_w
author_rank: Super Contributor
timestamp: January 09, 2024, 11:46:48 pm
content: This just seems incredibly unsafe and not really worth the effort. Have you tried a regular light dimmer to see if that would work? Have you looked at the cost of buying a normal dimmable LED?These are linear regulator LED chips, you can search for Bigclive on youtube and he has a few videos explaining how they work.

author: themadhippy
author_rank: Super Contributor
timestamp: January 10, 2024, 12:00:49 am
content: QuoteOr just a suitable capacitor in series with the supply

author: badrequest400
author_rank: Contributor
timestamp: January 10, 2024, 12:15:02 am
content: Incidentally, the LED symbols are reversed on my attached image in the OP. The positive and negative sides of the LEDs are connected in the expected way to the electrolytic.I think it's impossible to do what I wanted; I'll just use the dim supply to power half the PCB.I don't think these chips are like the ones in BigClive's videos; I've encountered those before and their datasheets give them like seven differrent pins where as these have like four (since many of them are shorted, maybe internally, maybe on the PCB; not the same as the BP2861 for example for which all pins are distinct).I don't want to use any other dimmer or anything. I'm going to have a bright mode and a dimmed mode which will use a radio/radar occupancy sensor. If I used a dimmer, I'd have to make two adjustments every time I wanted to change mode.

author: themadhippy
author_rank: Super Contributor
timestamp: January 10, 2024, 12:33:49 am
content: QuoteIf your plan is to have the light automaticly switch from dim to full when the occupancy sensor triggers just simple make the detector bypass the dimmer/capacitor

author: badrequest400
author_rank: Contributor
timestamp: January 10, 2024, 12:35:25 am
content: The plan is to have a bright mode and an automatic/dim mode. The bright mode will not be automatic.