Turning a florescent replacement type A LED T8  into a type B - Page 1
Forum section: electronics / beginners

author: dclevy1
author_rank: Contributor
timestamp: July 15, 2018, 02:51:21 am
content: Is there a way I can turn a type a t8 LED strip into a type B strip. I want to be able to use 120 volt from Mains directly to the light like you can with the type B lights. Maybe reverse-engineer or remove a certain component from the board or add a really cheap component. The reason I ask is because I have tons of these type A lights because they were on clearance at a local store. But I want to be able to wire 120 to the lights because like I said before I have a bunch of these lights and I don't want to have to spend a whole lot of money on ballasts.Sent from my iPhone using Tapatalk

author: edavid
author_rank: Super Contributor
timestamp: July 15, 2018, 03:55:55 am
content: You can buy a good ballast for $11 or so that will run 4 strips. Hard to see how you could build anything cheaper than that.

author: dclevy1
author_rank: Contributor
timestamp: July 15, 2018, 04:00:29 am
content: Quote from: edavid on July 15, 2018, 03:55:55 amI see what you mean but the way I want to implement them will be far apart from each other and I am trying to convert multiple areas of my home to LED T8 so the 11 or so dollars is going to add up really quickly. And what I mean by far apart I mean I will be making custom fixtures that will require me to destroy the outside of the bulb so that it is just the strip left behind. So I have no issue with modifying the strip to accommodate 120 voltSent from my iPhone using Tapatalk

author: dclevy1
author_rank: Contributor
timestamp: July 15, 2018, 04:03:14 am
content: I literally have 30 of these bulbs that I want to do something weird with LOLSent from my iPhone using Tapatalk

author: Cody Turner OKC
author_rank: Contributor
timestamp: July 15, 2018, 03:24:20 pm
content: hi, I have one of these that i wanted to try and use for a bench light over my desk, i reverse engineered it and got it working i can send you the schematic for mine

author: amyk
author_rank: Super Contributor
timestamp: July 15, 2018, 04:20:05 pm
content: First of all, what's the definition of "type A" and "type B"? Me and probably others here are not familiar with that term.If you mean the former has a built-in current regulator and the latter doesn't, then add one. It could be as simple as a series capacitor or resistor, depending on the current required. I see a bridge rectifier, two diodes (?), some capacitors, and a 3-pin SMD. Getting the part number of the latter would be very useful.

author: dclevy1
author_rank: Contributor
timestamp: July 16, 2018, 05:34:05 am
content: Quote from: Cody Turner OKC on July 15, 2018, 03:24:20 pmYes definitely do you want my email? I'm not very good at reading schematics but I'll try. When you say you were reverse-engineered at what are you using to power it now?Sent from my iPhone using Tapatalk

author: dclevy1
author_rank: Contributor
timestamp: July 16, 2018, 05:42:01 am
content: Quote from: amyk on July 15, 2018, 04:20:05 pmOkay type A are LED T8 bulbs that require a ballast to operate because they are supposed to be easy to retrofit into pre-existing fluorescent light fixtures. Type B bulbs are LED T8 bulbs that can be wired directly to 120v ac Mains voltage and you are able to bypass a ballast completely so you can use it as typical lighting. If you are willing to help me do you need the item number or model number on the components themselves?Sent from my iPhone using Tapatalk

author: Kjelt
author_rank: Super Contributor
timestamp: July 16, 2018, 08:54:26 am
content: It should not be such a great difference, buy one type B and compare, probably even the same PCB with a few additional components or even less components

author: eKretz
author_rank: Frequent Contributor
timestamp: July 16, 2018, 11:30:41 pm
content: I've got some T5 LED bulbs that I need to do this with. I think there are now than two types actually - there's the ones that can run directly from line voltage and I've seen a couple variations that can run from different kinds of ballasts - regular and "instant-on." I ended up with the wrong LED bulb style for my fixture apparently. With my fixture and this bulb type, when the switch is turned on, the LEDs flicker but don't stay on. If I switch the fixture a bunch of times, eventually they will "catch" and stay lit. I'm guessing they need to be switched on when the AC cycle is in just the right place.

author: amyk
author_rank: Super Contributor
timestamp: July 17, 2018, 01:22:55 am
content: Quote from: dclevy1 on July 16, 2018, 05:42:01 amThat makes it much clearer, thanks. In other words, type A are the ones which don't have a current limiter and rely on the ballast for current limiting, while type B does. Depending on the rated current and voltage, a capacitor or resistive dropper would probably be suitable, but once again you need to post that information.QuoteThe marking on the component itself. A clear high-resolution picture would be preferable.

author: Kjelt
author_rank: Super Contributor
timestamp: July 17, 2018, 06:53:09 am
content: Quote from: amyk on July 17, 2018, 01:22:55 amThe cupper/iron ballast is nothing more than a coil. You don't know what the coil does in serial with the tube.It could for instance drop the voltage with 20V or so, in that case they would have fitted less leds in the serial led string.That is why I say, buy one type B and compare it:- pcb equal ?- components missing , different or additional components ?- are the amount of leds equal ?- is the Vf of the leds equal ?that kind of things. Ofcourse you can just put it on a DC supply with current regulation and see with what voltage/current it reaches its nominal power.

author: edavid
author_rank: Super Contributor
timestamp: July 17, 2018, 02:32:33 pm
content: Quote from: amyk on July 17, 2018, 01:22:55 amNo, a capacitive or resistive dropper is not suitable. These are 32T8 replacement lamps, so they are probably rated about 18W. They need a proper power supply (SMPS with constant current output).Quote from: Kjelt on July 17, 2018, 06:53:09 amThe "Type A" LEDs only work with electronic ballasts, not magnetic ballasts.

author: amyk
author_rank: Super Contributor
timestamp: July 18, 2018, 12:32:34 am
content: Quote from: edavid on July 17, 2018, 02:32:33 pm18W @ 120V is 150mA, which is at the high end but still within the usual currents that capacitive droppers are used for.(I'm more used to 240V circuits where the current is halved, <100mA is definitely possible with a cap dropper.)

author: james_s
author_rank: Super Contributor
timestamp: July 18, 2018, 02:46:08 am
content: Quote from: Kjelt on July 17, 2018, 06:53:09 amT8 tubes longer than 18" in the US use electronic ballasts. The larger diameter T12 tubes above that length used autotransformer ballasts. The choke ballasts that are still very common in many parts of the world need more than 120V for longer tubes.

author: dclevy1
author_rank: Contributor
timestamp: July 18, 2018, 07:04:13 am
content: Quote from: amyk on July 17, 2018, 01:22:55 amI will take better pictures on Friday because the camera on my current phone is broken and I'm getting it fixed on that daySent from my iPhone using Tapatalk

author: dclevy1
author_rank: Contributor
timestamp: August 04, 2018, 05:36:09 pm
content: Quote from: dclevy1 on July 18, 2018, 07:04:13 amOkay guys sorry for the long Hiatus but I was able to find a DC negative and positive output to the actual LED array and test voltages. I found that the strip that I want to use is being supplied around 80 volts dc so that means it is powered through parallel and series connections.. so I need to find a high voltage DC Supply can anyone help me out with this.Sent from my iPhone using Tapatalk

author: james_s
author_rank: Super Contributor
timestamp: August 04, 2018, 05:42:40 pm
content: If you're going to add a DC supply why not just use a ballast?Otherwise you could take apart a screw in LED bulb and use the driver out of that, or you could try a capacitor dropper.

author: dclevy1
author_rank: Contributor
timestamp: August 05, 2018, 02:59:46 am
content: Quote from: james_s on August 04, 2018, 05:42:40 pmI won't use a ballast with the existing fixtures that I have because I am completely taking it apart and I want it to be easy to accommodate other strips and parallel other strips. That's why I want to use a DC Supply and it all depends oncreative things I want to do with the strips as well so I like to have options. Out of the variety of three different brands of LED T8 I've taken apart I like these the most. These are Sylvania older LED T8 retrofit bulb strips. Sorry for the shity photos my camera on my iPhone is really screwed up. But I hope y'all figure out what I'm trying to do or figure out what this strip is. The strip looks like it has a bridge rectifier on it but then again I don't know a whole lot about ElectronicsSent from my iPhone using Tapatalk

author: james_s
author_rank: Super Contributor
timestamp: August 05, 2018, 04:21:13 am
content: You'll need to reverse engineer the circuit and draw a schematic to see what it is. It looks like you're going to need a constant current source though, ie a ballast. That doesn't necessarily mean a fluorescent lamp ballast but you will need something to provide a constant current with the ability to supply at least 80V. If you don't know much about electronics though I can't say I recommend this project, it involves voltages that could potentially cause injury or death, and a fault due to a poorly designed driver could start a fire. Don't take this the wrong way as I encourage learning but this is one of those things where if you have to ask, you maybe shouldn't be messing with it.

author: dclevy1
author_rank: Contributor
timestamp: August 05, 2018, 07:02:47 pm
content: Oh yeah I understand completely but I do understand voltages and different amperage the harm they can cause bodily wise. I do know about different components and what they do and DC and ac voltage as well so I'm not a complete noob. What I don't understand is reverse engineering and how to really draw a schematic I understand the idea but not exactly how to do it. That's where I need you guys help but from there I know how to be safe with these type of things. But if I can make it easy on myself and find a supply from AliExpress or somewhere trusted that will get me by on my crazy projects that'll be great. Just to be 100% sure why do I need a constant current source.Quote from: james_s on August 05, 2018, 04:21:13 amSent from my SM-N910P using Tapatalk

author: Kjelt
author_rank: Super Contributor
timestamp: August 05, 2018, 07:04:16 pm
content: I agree with james-s you end up with unisolated 80V drivers that can kill even with 50mA's.I abandoned a project like this a few years back and redesigned it to 36V which makes it safe (cheap isolated dc power supply) and easy to make adj. current with a lm317.

author: Kjelt
author_rank: Super Contributor
timestamp: August 05, 2018, 07:08:19 pm
content: Normally these power supplies are fed with rectified mains busvoltages, that is around 360V for 230VAC in and from that busvoltage a dc-dc converter generates the 80VDC current regulated. If you look at the components used in a commercial supply to do this right it are two hundred components, microcontroller with software and at least a year of finetuning and testing, again: NOT recommended for DIY unless you work in the field and have plenty of experience.