Convert LED lamp from 230V AC to 12V DC - Page 1
Forum section: electronics / repair

author: dredd
author_rank: Contributor
timestamp: March 28, 2022, 03:15:28 am
content: Hi.I was searching for a perfect 4WD reversing light to put at back of my car and bought this 30W unit. I thought I'll be seeing some kind of PSU which I would bypass. But it looks like magicHow do I power this thing by 12V?Reason I bought 230V is I could not find well made 12V one, I already got some ebay thing that is just 12W and flimsy made.Thanks!Edited:Adding ebay link:https://www.ebay.com.au/itm/154906042148?var=455029498756

author: james_s
author_rank: Super Contributor
timestamp: March 28, 2022, 03:34:49 am
content: That looks like it's going to be difficult to convert, it's a series string with a linear regulator. To convert you'd have to break up the chain and wire the sections in parallel with separate resistors for each section, or build a boost converter that will get you ~240V.

author: inse
author_rank: Super Contributor
timestamp: March 28, 2022, 05:24:21 am
content: I agree on that, just wondering about the silkscreen "9V 18V" at the top.Maybe there are low voltage versions available as well?

author: james_s
author_rank: Super Contributor
timestamp: March 28, 2022, 05:45:54 am
content: That's a good question, I didn't notice that before. Maybe this has multi-chip high voltage LEDs installed and with single chip LEDs it can be configured for a lower voltage? You'd have to trace out the circuit and take some measurements to determine exactly what's going on, but either way I doubt conversion will be feasible.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 28, 2022, 07:58:12 am
content: 24 LEDs in series would be some 80 V, which would be OK for the 110 V case. If they have inside the LEDs 2 crystalls in series it would fit the 220 V case.Chanes are the 9 V / 18 V version would need a different PCB and also other changes as the regulator part would be different.I somewhat doubt the conversion is feasable - it would likely end up as a new PCB with new LEDs and reusing the case.

author: dredd
author_rank: Contributor
timestamp: March 28, 2022, 12:01:21 pm
content: Thanks, looks like no easy way to do it ... I'll start checking voltage in some spots.

author: Haenk
author_rank: Super Contributor
timestamp: March 28, 2022, 12:48:27 pm
content: A converter 12V -> 230V is not too expensive if you can't find a good 12V replacement.

author: wraper
author_rank: Unknown
timestamp: March 28, 2022, 01:01:19 pm
content: Quote from: Haenk on March 28, 2022, 12:48:27 pmBut it's a complete waste to buy one for powering this garbage. Probably LEDs are sort of OK when powered from low voltage DC with 2x reduced power. But it's a flickering junk when powered from AC. Power rating is likely fake too, not that you should want higher power consumption since these lamps often have terrible efficiency.

author: Haenk
author_rank: Super Contributor
timestamp: March 28, 2022, 01:06:03 pm
content: I agree, since these are so cheap, it's certainly better to buy the same stuff as 12V versions.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 28, 2022, 01:56:12 pm
content: Replace the LED module with a 100W DC version (about 30V) and then get a constant current boost converter to run it. Run it at something like half its rating to allow tolerance for higher temperatures.

author: tooki
author_rank: Super Contributor
timestamp: March 28, 2022, 06:21:08 pm
content: Or just remove the PCB entirely and replace it with a 12V COB module that fits. By far the better solution.

author: mariush
author_rank: Super Contributor
timestamp: March 28, 2022, 08:34:26 pm
content: Well, it wouldn't be impossible to make it work, but would require a bunch of modifications.First thing you would need to do is figure out the forward voltage of each led (it's probably 2 or 3 tiny leds in each package, making each led require 6 or 9v to work)It looks like it starts from top right and you have 2 leds in parallel , then these 15 groups are in series and you can sort of see a traces going from the 4th group on the right, back to the 2nd column of leds from the right and so on.So in theory, you COULD use a sharp knife or something to CUT that trace that goes from the 4th group of leds back to the top and then cut the trace that goes from bottom of middle column to the top of first. ... and you can now join the 6 columns at the top and at the bottomSee picture below ...Your "panel" would now need at least 4 x forward voltage of one led, so at least 4 x 3 / 6/ 9v ... worst case 36v ... but the current is much higher. Let's say 100mA per led (because original design says 30w and it's 30 leds so 30 leds x 9v x 0.1A = ~ 27 watts if there's 3 diodes in each package) , you're looking at 6 columns x 100mA per led = 600 mA ... but you don't need to drive them that hard. Even at 50-60mA per led it would still be quite bright.So you'd want to look for a led driver that can do 15-30w and let you adjust current to around 300-600 mA of current.For example :https://www.ebay.com/itm/133163263125?hash=item1f01262495:g:tPEAAOSw9Xhdc1CzThe 20w version claims output 20...40v , max 600mA so if you're lucky the chain of 4 leds has the forward voltage below 40v ... or you could just desolder the last row and solder jumpers instead to have 3 leds in series.

author: dredd
author_rank: Contributor
timestamp: March 29, 2022, 03:43:20 am
content: Quote from: Haenk on March 28, 2022, 01:06:03 pmTrust me, I triedI am now returning some of it, total junk. But this enclosure is really well made, real thick glass and rubber seal. And brightness actually looks like real 30W. And I searched for 12V version, these are were in 230V versions...

author: xavier60
author_rank: Super Contributor
timestamp: March 29, 2022, 09:56:09 am
content: What are the ICs?

author: dredd
author_rank: Contributor
timestamp: March 31, 2022, 08:16:57 am
content: Thanks all, bought this 30W/12V LED module on Aliexpress for $5 as a solution.https://www.aliexpress.com/item/4000251299260.html