Kitchen Lighting…

The kitchen lights over the sink and stove worked fine when I moved in but it soon became apparent that there were going to be problems with them. Mainly, there wasn’t enough light. Over the stove there’s a small obscured window under the MW/Convection oven that is held in place with one screw. Remove that screw, the window and frame that holds it open to reveal that there’s two 120 volt candle base type bulbs. They’re about 2″ long. Now, my experience with incandescent in a RV is that they work fine, until they burn out. And then it becomes difficult to find them on the road because they are often RV type ‘semi-custom’, meaning that most stores don’t carry them.

And over the sink there’s a 12 volt dual fluorescent fixture. I can tell it’s a 12 volt fixture because it’s still working when I’ve unplugged from shore power…and verified that there’s not an inverter feeding it. Inside the fixture are two fluorescent bulbs of 12″ long. The fixture has a built in inverter circuit to bring the voltage up to light the fluorescents. Again, difficult to find those small and short tubes while traveling, and too delicate to safely store in my RV. Plus I’d probably forget where I’d stored them. Finding replacements on the road was going to be a trick.

Since incandescent and fluorescents are being phased out and slowly disappearing from the market, replaced by much more efficient LEDs, I opted to get ahead of the game and started looking for LED replacements outside of the RV markets.

Often the LED replacements are very expensive, comparatively. But eventually, I got a lead on a nice little automotive (12 volt) light strip at eBay that only cost me $5.70 for a box of 2. Bought two boxes. Wanted to see how reliable they are before committing to many more…

You can see from the lighting in that picture that I used the light from the incandescent above the LED to show them off. Ironic juxtaposition?

Stove lighting…

The stove is going to be tricky because the lamp assembly is all part of the MW/Convection oven that includes the fan. It’s a bit tricky getting the cover off but once that’s done, then there’s also the challenge of finding a place to mount stuff inside there. I had to use a bathroom mirror in order to not get a crick in the neck. You can see that there’s plenty of room inside the lamp housing to fit both the new LED strip (shown above), and the necessary 120 to 12 volt conversion circuit. I left the bulb sockets in the housing and spliced into the wiring to the bulb sockets to obtain the necessary 120 volt AC. Switched Off/On by a domed pushbutton on the face of the MW.

I didn’t worry that the product only came as 12 volt lighting strips because I have several places in my RV where they could go with nearby 12 volts available. Plus, if I needed to use one in a 120 volt AC position, I have the skills and parts available to accomplish that. And that’s exactly what was needed for the under oven-over stove light.

First thing was to find a method of dropping the voltage available in the light housing down to 12 volt required by the LED strip. And this proved to be an expensive series of screw ups. I dug through my many junk boxes and almost immediately found a sweet little power module that converts 120 volt AC to 12 volt DC. Just what I needed. And I hooked it up backwards while testing and blew the transformer inside. Gah!

Next, I found a 120-12 volt transformer in my parts stock. Added a couple discrete electronic parts, and voila’ it’s a 12 volt power supply small enough to put inside the lamp housing under the MW. And I wired it up backwards during one test and burnt up the transformer. GAH!

My electronic skills seem to be fading due to lack of practice.

OK, I have one more 120-12 volt transformer so made sure I wired it up right and completed my little circuit. Finally. You can see from the schematic that it’s not all that complicated.

Yea! Light!

I used point to point wiring so no circuit board is used, just soldered everything together connecting to the terminals on the transformer and the wire leads of the components. And then soldered on the wires from the LED light strip.

After that was done, drilled a couple holes to mount the transformer, wired up to one of the bulb sockets, spliced into the 120 volt wiring and…we have light!

It’s about as bright as the two bulbs I’ve removed so no gains there, but the LED strip should last much longer. I did find that trying to stick the strip to the metal housing put it too far away from the glass window. So I just cut a couple of small pieces of double stick tape and now the strip is stuck right on the back of the glass allowing as much light from the LED as possible to reach the stove top. It’s rated for 10,000 hours so I may never have to replace it.

Over sink fluorescent fixture…

Shortly after accomplishing the over stove light swap to LED, one of the fluorescent tubes burnt out. This may have something to do with the fact that I use that fixture to light the living room during the evening and night while I’m watching TV. I don’t like the TV to be the main light source in the living room. The 12 volt bulbs are bright enough, but they do get hot, and the tiny flood lamp bulbs are going to be hard to find if they burn out from overuse. And the ceiling fluorescents aren’t the best to use as they aren’t all that common either so would be hard to find on the road. Especially as the world switches over to LED lighting.

The solution is to install LEDs in place of the fluorescents and I just bought the perfect kind! Handy. And this redesign won’t be all that perilous either because I knew the fixture operates on 12 volt. So no dealing with an inverter design.

There’s four wood screws holding the fixture to the bottom of the upper cabinet. Removing the tube cover gives access. After those are out, it required some prying with a putty knife as the cutout was an exact fit and the fixture didn’t come out easily. Once out, it’s much easier to work on then the over stove fixture because it reaches the countertop. Detached the center cover over the inverter circuit board and cut the two 12 volt supply wires coming from the off/on switch mounted to the fixture. I’ll use those wires to supply power to the LEDs. I planned on using two of them for added light over the sink.

And this is where I mounted them. They have sticky tape on the backs running the length of the strips so it’s just a matter of peel and stick. The leads are very fine wires not suited to ‘just’ a wire nut, so I soldered them to the supply wires. And then capped them with twist on wire nuts.This is what it looked like during testing with both LED strips ON. 

After that, installed the original internal cover to hide the circuit board and hold the wires…

After reinstalling the fixture, it was getting near dusk, so I left the lights on. Nice and bright. I can live with these. And soon discovered that they get far too hot to survive very long. The sticky tape melted enough that the strips detached from the fixture and fell down onto the lens. I noticed just before the lens started to melt from the heat.

I ran a current test and found with 13.6 volts supplied, the two LEDs were consuming 0.9 amps total, which means 0.45 amp each. They are rated at 0.5 amps max but were so warm (hot?) that they would probably burn out in short order, or so I felt. It might just be a matter of finding a way of cooling them but I didn’t want to go to the trouble. I’m not sure why the heat wouldn’t also shorten the lives of this automotive product in a car as most cars would also have 13.6 volts from the alternator running these strips like mine were seeing from the converter (a battery charger all RVs have that’s on continuously when plugged into shore power and that supplies power to all the 12 volt devices, like lights). But the ads talk about them having a long life. My judgement was that they were too hot to last long in my application.

Hmm, well, I did like all that light though. But, I don’t want to be replacing them too often. So I checked my junk bins and found a On-Off-On switch about the same size as the original Off-On switch in the housing and swapped them. Then I wired up a couple diodes in such a way that I have two brightness settings for my over-the-sink light. First there’s off of course, then one switch position allows 0.6 amp to both LED strips, and the other switch position allows 0.4 amp. So when I need more light, I switch it to the high setting, the rest of the time, to the low. Best of both worlds and less chance that they will burn out too soon. The wiring was trivial and finished in a matter of minutes. After several hours of operation where I’d check temps and verify they weren’t too high, I think it’s going to work fine. And give me thousands of hours of operation without failing. This schematic is how it’s wired up, with added parts, to decrease operating current and adding the feature of Hi/Lo brightness.

So that’s my method of replacing the fluorescent tubes with LED strips. Inexpensively. With very long operating lives.

The strips are 6 & 1/4″ long, and output enough light that I think I would be able to use 4 of them in each 18″ ceiling fluorescent fixture without losing much brightness. I could run them a little closer to 0.5 amps too by using a single diode or a resistor of appropriate value. We’ll see.