Modifying my new shop lights

[Kitchen Panda]

My electronics workbench in the basement was lit by two twin-tube T5 fluorescent lamp fixtures. These gave lots of light, probably around 9000 lumens between the two fixtures, in a room 6 feet by 10. The light level was OK but the lamps gave off a lot of radio frequency interference. For example, we used to watch TV in the basement on rabbit ears - if the shop lights were on, TV was wiped out. I couldn't even have a portable radio on while the lights were on, and my VHF/UHF scanner was useless. (Yeah, the answer there is an outdoor antenna....I'm working on that.)

It was so bad, I could see interference on my oscilloscope if the shop lights were on.

A friend of mine had replaced his basement shop lights with LEDs and I checked with my ham radio HT and found the radio noise level in his basement was low to non-existent. So clearly I needed to change my shop lights for LEDs. I had often seen cheap LED shop lights in the DIY flyers each week, but they listed fairly low lumens - I would have needed 3 or 4 lamps to match the lumens of the T5 lamps, and I didn't want a row of luminaires as my ceiling.

I picked up two Feit SHOP/4/HO/850/CAN at my local DIY store and proceed to hang them up. These were specificed as 12,000 lumens. I replaced the T5 fixtures with a duplex plug for the cord sets on the new lamps. I didn't have head room below the suspended ceiling for the chain and hook mounts, so I had to use the keyhole slots and screws - putting them through the ceiling tiles and into a solid wood backing strip to prevent the screws from pulling out. I put an extra screw at the end of each lamp to stop them from working off the screw heads. I also tied the lamp to the ceiling T-Bars with a loop of paracord at each end, so the lamps can't fall if I bang into them by accident.

24000 lumens of 5000 K goodness. Great! Much less radio noise. I can hear a little bit of "frying"in the background on local FM broadcast if the receiver is close to the lamps, but out in the rec room all is well and the internal whip gives me clear quiet reception on local FM even sitting in a basement.

And tons of light - I have about 4 times the lux at my bench than I had before, according to my cheap light meter (which failed during the course of this installation).

Unlike some LED lights, there's no strobe-bar effect when using my digital camera - I like to take pictures of shop repair projects and sometimes do a video (If you get the chance to watch loading tape into a VHS machine with the covers off, do so!). A photo can help a lot when you're trying to remember which holes took the 3 mm-long screws and which ones took the 3.5 mm-long screws.

Maybe a little too much light. I noticed I have to switch off one lamp when using the oscilloscope. The extra light washed out the trace....even on an LCD 'scope with the brightness turned up all the way.

I'm a regular viewer of the "Big Clive" YouTube channel, where one of his favorite activities is tearing down cheapy LED lamps and showing how the internals work. He will often suggest changing the lamp driver to make them run at lower power, cooler, and presumably with longer life.

Inspired by YouTube, I took apart one of the Feit shop lights and discovered the electronics within. They use a chip called JW1606S to drive the switch-mode coverter for the lamps. After some Googling, I found an AliBaba ad for these chips that included the data sheet (not posted on the company Web site, who knows why?).

The data sheet let me figure out the current sense resistor is made of four parallel surface-mount resistors, three 1.5 ohm and one 1.2 ohm If I took out the 1.2 ohm resistor, the effective combination will go from 0.35 ohms to 0.5 ohms, which should reduce current by about 30%, and also reduce light output ( and heat).

This was successful. The lamp input power dropped from 120 watts down to 75. Lighting both lamps in parallel shows that the lamp is not putting out as much light, though I'm surprised a 30 or 40% drop isn't all that noticeable. I haven't compared temperature rise yet, but I'm hopeful the lamp will run cooler. It's not the LEDs that will fail first, I bet, but the capacitors in the driver. Radio noise is even lower than the un-modified lamp.

And best of all, now I can read the scope trace without taping a sun-shade over the screen.

(I was surprised again when the local ReStore recycling place wouldn't take the T5 fixtures....the lamps had to go to hazardous waste, and the fixtures went into the skip. Guess you can't buy T5 lamps any more? )

 

[Dave_H]

Not long ago I did some work in a lab involving sensitive measurements. When the (non-LED) bench fluorescents were on, interference around 59kHz was being picked up.

I've successfully lowered current in A19 LED bulbs which use linear CC regulators. Some bulbs which run hot and are too bright for the application, can be modified, with care I should add. They run cooler and should last much longer, and efficacy should be improved (moderately).

There are a host of Chinese companies making these ICs, but finding readable datasheets is not always easy. Sometimes the vendors do not post on their websites.

Dave

 

[Kitchen Panda]

Not long ago I did some work in a lab involving sensitive measurements. When the (non-LED) bench fluorescents were on, interference around 59kHz was being picked up.

I've successfully lowered current in A19 LED bulbs which use linear CC regulators. Some bulbs which run hot and are too bright for the application, can be modified, with care I should add. They run cooler and should last much longer, and efficacy should be improved (moderately).

There are a host of Chinese companies making these ICs, but finding readable datasheets is not always easy. Sometimes the vendors do not post on their websites.

Dave

Interesting! Yes, I've seen that the smaller LED bulbs use linear regulators, but this fixture is a switch-mode device; not sure what frequency it switches at, the data sheet pages I can see don't give that. I left both the unmodified and modified fixtures on for a few hours last night and I think the modified one is running at least 15 degrees C cooler than stock - my temperature measurement technique is pretty rude, just pressing a multimeter thermocouple probe up against the lamp housing. But this is consistent with my expectations.

Google Translate is a big help if you find a non-English data sheet, provided it can read characters and not just images..

 

[Dave_H]

Interesting! Yes, I've seen that the smaller LED bulbs use linear regulators, but this fixture is a switch-mode device; not sure what frequency it switches at, the data sheet pages I can see don't give that. I left both the unmodified and modified fixtures on for a few hours last night and I think the modified one is running at least 15 degrees C cooler than stock - my temperature measurement technique is pretty rude, just pressing a multimeter thermocouple probe up against the lamp housing. But this is consistent with my expectations.

Google Translate is a big help if you find a non-English data sheet, provided it can read characters and not just images..

Always interesting to hear of people opening devices to see how they work, how constructed,
and sometimes doing useful mods. It's too bad the makers on shop lights do not (that I have seen) provide a high-low switch, not that complex/expensive, I suppose every penny counts...

Closest I can find is 2-page "datasheet" (if you can call it that, it is more of a "product
brief") for JoulWatt JW1600 (not 1606S). Would there be a link for the correct one?

I don't have much need for long shop-lights but have a couple, one using replaceable 4-foot
T8 direct-wire tubes. The current trend is non-replaceable, the whole fixture goes out when something fails.

For temperature measurement, you could try an IR thermometer. Princess Auto sometimes
has good deals on them. Only caution is the emissivity is usually fixed at 95%, shiny targets can cause inaccuracy.

Dave

 

[Kitchen Panda]

Always interesting to hear of people opening devices to see how they work, how constructed,
and sometimes doing useful mods. It's too bad the makers on shop lights do not (that I have seen) provide a high-low switch, not that complex/expensive, I suppose every penny counts...

I thought about adding such a switch - but that would have meant attaching flying leads to the rather small SMD pads on the board. After factoring in how often I'd actually use it (as opposed to just turning off the light and using a desk lamp), the messy business of mounting an externally accessible switch, and my natural laziness, I decided the single brightness mod was sufficient for my purposes. Since there are two lamps and each has a pull chain, I can turn off the un-modded 12000 lumen unit and just leave my nerfed one for right over the bench - and fire up both lamps if I'm doing bench photos or something that can use the light. In retrospect, putting 24,000 rated lumens into a 6 foot by 8 foot room might have been to much (works out to up to 500 footcandles - good for difficult assembly operations,sewing of textiles and gloves, or autopsy tables, according to the old IES handbook.

I wouldn't be too hard on the manufacturers, lighting up a garage or a reasonable sized shop would be a better application for so much light, and in those cases you'd rarely need to step the brightness down.

Closest I can find is 2-page "datasheet" (if you can call it that, it is more of a "product
brief") for JoulWatt JW1600 (not 1606S). Would there be a link for the correct one?

I didn't keep a link - it was an AliBaba ad and those melt away like dreams. If I were looking for it again I'd just type in the full part number and trust the Google.

I don't have much need for long shop-lights but have a couple, one using replaceable 4-foot
T8 direct-wire tubes. The current trend is non-replaceable, the whole fixture goes out when something fails.

The last time the T8s burned out in my laundry room, I bought a pair of LED tubes to replace them. They have an odd interaction with the radio-controlled switch for the laundry room lights (fixing the consequences of a door hung opposite the way the reno drawing showed...put a radio light switch on the other side of the door because to me that was easier than digging up drywall to move the hard-wired switch). About 1 time in 5, the LEDs don't go completely off but stay lit at maybe 1% of full brightness. This is doubtless due to the TRIAC in the radio control leaking a little bit...sometimes. Haven't got round to fixing this yet.

The other weird interaction between LED lights and remote control switches was the strings of LED bulbs I put up in the rec room, then used an old Home Link remote control on them. Worked well, but I noticed one LED in each string of 60 or so was still lit even when the remote was switched off. I did eventually discover this LED was wired *backward" to the way the rest of the LEDs in the string were connected; guess there was enough leaking throught the TRIAC to light one LED but not 59.

Throw-away lamp fixtures do bother me on some level, but remember we used to think throw-away cigarette lighters or pens were absurd. If the capacitors in the power supply hold up, the lamp could last 15 years or more....changing a whole fixture every 15 years is about as much labor as changing a bulb 2 or 3 times a year.

For temperature measurement, you could try an IR thermometer. Princess Auto sometimes
has good deals on them. Only caution is the emissivity is usually fixed at 95%, shiny targets can cause inaccuracy.

Dave

The first IR thermometer I ever used was a big ugly Leeds and Northrup disappearing filament pyrometer! Yes, I have picked up one or two Princess Auto thermometers - the problem is the surface I'm most interested in measuring is inaccessible to view by an IR thermometer. In my steelmaking days we learned the trick about putting a piece of painter's tape or a bit of flat black paint on a shiny surface to make it more compatible with the default emissivity setting - that doesn't work when you get up to disappearing-filament-pyrometer temperatures, mind. Tends to burn off.

LED lighting gets you involved in so many other things.