Flummoxed by fluorescents, baffled by ballasts - Page 1
Forum section: electronics / projects

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 18, 2016, 02:50:31 am
content: Confused by connectorsSo I finally installed the T8 LED lights at my parent's place. I eventually got them to light up, after filing the new sockets down to fit the fixture. But here's what's baffling.The wiring diagram is as followsThis is standard stuff. An actual household bulb has two pins at each end, which connects to the filament inside. The ballast has single wires which push right into the new sockets I installed. On the red end I simply used the excess red wire to jumper across the two connectors. This worked great for the old tubes I tested. Lights right up. This is with one wire connected to one pin on each connector, which should be fine.But the LEDs didn't turn on until I shunted each pin of each connector. WTF?I know the sockets have individual connections for all the different kind of magnetic and rapid-start and what not ballasts, but instant start is all about just slapping 600V across the bulb.What is inside the LED bulb that it can tell the difference and why is it wired this way? It means it is not a direct replacement since you can have a working fluorescent setup that will not work with a simple swap to LEDs, even though it is written on the box "for instant start ballast".I don't get it. Must be something very simple since I can't figure it out.The LEDs are super bright, and no problem after 30 minutes, no smell, smoke, buzzing, or excess heat.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 18, 2016, 03:36:42 am
content: It's a classic inverter fluorescent driver. The (auto)transformer secondary connects to the blue wires through series capacitors. The red wire connects to the other end of the secondary. LT has a bunch of app notes relating to fluorescent lamp drivers if you want to know more.Most likely the LED drop in modules happen to use just one pin on each end. They can't just short the two pins together since that will short the preheat windings on drivers that have them.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 18, 2016, 04:05:22 am
content: The LEDs are specifically designed for instant start ballasts and it says so on the box. But you're right, the only thing that I can see that explains it if there is indeed a dummy load in the LED bulb that needs to be shorted out. It would prevent disaster in case the LED is plugged into the wrong kind of ballast.But it really needs to be more clearly spelled out on the box, because I initially just went with the idea that only one pin needs to be connected.

author: jdraughn
author_rank: Regular Contributor
timestamp: October 18, 2016, 08:04:13 am
content: FYI, the connectors inside the big 4 pin connectors on PC power supplies (RED, BLACK, BLACK, YELLOW) that plug into CD-ROM's and such are the perfect size for most fluorescent bulb pins, I remove them from the housings and use heat shrink around them.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: October 18, 2016, 08:40:10 am
content: Quote from: Alex Eisenhut on October 18, 2016, 02:50:31 amI have done 2 styles of LED replacement tubes. Both times I bypassed the original ballast and replaced the starter with the LED fuse.1 was wired only at 1 end. The other end was no contact.the other one was active one end, neutral the other.They should have instructionsanda fuse.They do look better than real tubes, especially better than with the magnetic ballast fittings.