Screw Light

My Light Stand

Osmany is working on the vaulted ceiling and I'm thinking he could use some better light. 

Harbor Freight Halogen Work Light $37
Similar to the one we got from Home Depot 3 or 4 years ago for $65, but Home Depot doesn't carry them anymore. All their work lights are LEDs.

We have a couple of old halogen lights that came off of a cheap work light from Home Depot. 

AmazonCommercial 2000LM LED Work Light $16

We replaced those with some LED lights from Amazon because we got tired of paying $10 for a new halogen bulb every couple of months. 

300-Watt 4.7-Inch T3 Halogen Bulbs (5 Pack) $10

I also bought a pack of halogen bulbs from Amazon at the same time I bought the LED lights. I was operating under the dag nab it, we-need-more-light directive. So now I've got a pile lighting stuff, and I see we could use very tall work light, so I look around and I find a ten foot length of two-inch ABS pipe. That would be perfect. Now all I need is some scrap lumber to fashion a base and a cross bar and we should be good to go. With judicious use of a skilsaw and an electric screwdriver I was able to construct the base and the cross bar. Now all I need is a couple of wing nuts to secure the lights to the cross bar. And a switch box.

Switch box inside

It all went together well, but it didn't work, so the debugging began. First problem was the outlet I used had had been de-tabbed. Normal double electrical outlets are joined electrically by a tab. If you want one outlet controlled by a switch, you can break off this tab. No big deal, I can join them together with a bit of wire. Only problem is the number of screws that need to be removed and reinstalled to get this done.

Contact point and plate held by needlenose pliers

Now one of the lights doesn't work, and then the other one fails to light up, so I open them up, disassemble them and attack the points that contact the halogen bulb with a file. One contact has melted, so I replace it with a screw that I cut to length and then ground a sort of tip on it using an angle grinder. 

Lamp holder inside lamp body

Reassembling the points into the lamp holder requires placing a tiny nut in a hex recess in the ceramic block. You do this by setting the nut on top of the sharp point of a drywall screw and then sliding it up into the recess. Then you turn the ceramic piece upside down and replace the screw with a pencil size stick to hold the nut in place while you connect the wire to the contact with a screw. Tedious bit of fiddly work, perfect for a puzzle player.

5 1/2" Double Ended Halogen Socket with Bracket (2) $8

Things still aren't working, so I order some new lamp holders from Amazon. I mean I still have $10 worth of halogen bulbs left and I need to get my money's worth out them. Go through the same rigamarole that I used to get to the contacts so I could file them clean and install one of the new lamp holders. Still no light. Finally get the volt meter and check the switch - she's kaput. Well, a switch ten feet in the air is not very useful, so I take it out and patch the hole in the plastic switch box with duct tape. 

Finally we have light!

There must be a hundred screws in this simple little project.

P.S. This started as a simple little project I thought I would be able to throw together in an afternoon, but as it was it probably took me 8 hours spread over a week to gather all the pieces and screw it all together. It would have made more sense to just buy a couple more LED work lights and put them on the stand than to fuss with resurrecting these halogen fixtures. I think the problem with the halogen fixtures started when the first bulb burned out. I went to Home Depot to pick up a replacement. I think the original light came equipped with 350 watt bulbs, but they didn't have any of those. They had some 500 watt bulbs. More is better, right? They were bright but halogen bulbs are hot, and those 500 watt bulbs were really hot. I suspect that's what melted the contact points. I probably could have saved myself an hour or two by just going straight to buying the replacement lamp holders, but who'd a thunk that such things were even available? I certainly didn't. But like I said, fiddling with those was like working a jigsaw puzzle, tedious but rewarding in a pointless sort of way.

Service Calls

The O-man came by today. He wanted to get the oil changed in his car. I advised him to call Eric Heaton and schedule an appointment. I suspect that he drove out here to visit Eric's in person because he is like me, he likes to deal with people face to face. And he might have been able to get the oil changed on the spot. It used to be that sometimes worked. Lately though he's been very busy.

Whatever, we've got company, let's put him to work. What can we do? Well, for starters there's that floodlight over the driveway that's been burned out for a couple of days (weeks? months? years? how about friggin' decades?). Last time I worked on this, I wasn't getting any juice to the fixture. It was one of those "there's nothing wrong, but it doesn't work" situations. And then the inside of the attic where the light is mounted got plastered over, and, well, yeah, that kind of put paid to that project.

But today we got out the ladder (substitute 'O-man' for 'we' whenever the story includes someone actually doing something). We climbed the ladder, replaced the bulb, and boom! 500 Watts of halogen in your face! (I just learned that Halogen is spelled like halo, so halogen is like an abbreviation for 'halo generator', or maybe 'halo genesis' if you're into Latin.) The light switch has been sitting on 'ON' all this time. Probably should have checked beforehand. On the other hand, while turning the switch off beforehand would have eliminated the smack-in-the-face, it would have meant doubling the effort, as some would have had to:

• run up the stairs to turn off the switch.
• run back down the stairs to steady the ladder, while
• his partner climbs the ladder, replaces the bulb,
• climbs down.
• Now number one runs back up the stairs and turns the switch on.
• His parter confirms that the light is on, but number one can't really see it,
• so he runs back downstairs to see that the light is working,
• runs upstairs to turn off the light
• runs back downstairs to acclamation and celebration!

The bulb is a flower, very delicate, and during our first attempt it got cracked right near the end of the glass envelope. This allowed it to work for a few minutes (Hip, hip, hooray!) but eventually either the halogen leaked out or air leaked in (or maybe they were just exchanging ions as molecules are wont to do) and it appears the element combusted.

Halogen 500 Watt floodlight bulb after all the Watts escaped.

Down, but not out, we ventured once more into the breach, climbed the ladder (after making sure the switch was off), and replaced the bulb. I left it on while my wife and I went to Amelia's for dinner this evening and it was still on when we got back, so maybe it's fixed.

The rain sensor is our next project. A couple years (decades?) ago, I replaced the original irrigation timer with a fancy new Rain Bird SST 600s. This new timer came with a 'sensor' that allowed the machine to adjust the watering cycle based on the weather. The old timer worked fine, it was an economy model and the numbers on the switches never aligned with the switch position. It was just kind of annoying. Then a couple people recommended these new fangled gizmos, so I let myself get talked into it.

Knowing how much the time the sprinklers are set to run is really kind of pointless because all you can do is adjust the time, but nobody really knows what a 'good' time is, so you have to experiment. Mostly it involves picking a random number and then letting it run for a few days (weeks? months?) until you notice that the lawn is waterlogged or turning brown. I really don't even need to notice, my wife or Rob Benton, our lawn guy, will make it a point to inform me. Kind of an odd situation. I am become Keeper of the Irrigation Timer!

Anyway, a red light appeared on the timer's control panel indicating the sensor was out of whack. We took it down, cleaned it and put it back and it seems to be working. It appears to use a couple of CC's of cork on a spring scale to measure the rain and a thermistor to measure temperature. The spring scale looks like it uses touch-pad technology to measure the deflection of the scale. Nothing but a nylon stylus sliding over some pads on the circuit board.

Now there's the garage door keypad. This thing has been trouble since day one, well day ten maybe. I had a lot of trouble finding one that would work, and then when I did, I found I had to reprogram it several times to get it to work. I quickly got tired of that program and just gave up on it. Nobody uses it, so it doesn't really matter. But gol durn it, I paid good money for that gizmo, it ought to do its job. So we open it up and poke and prod and look up the instructions on the Internet and reprogram it and it seems to be working. I think the instructions might be better than the ones that came with it.

We've done so well, maybe we should reward ourselves with a little basketball. Um, the ball's a little flat. That's okay, I've got a little 12 volt compressor we can use to pump it up. Except it plugs into the cigarette lighter in the car and we aren't getting any power. Check the fuses for both the cigarette lighter and the auxiliary power outlet and they are both blown. What the heck was the previous owner doing that he blew both fuses? I know, something shorted and the first blew, so since his machine died, he assumed the problem was with the outlet, so he plugged his machine into the second outlet and blew that one too. But then he crashed the car so it all evened out.

Inflation
No side hole

Needles
With side hole

We get new fuses, but now we have another problem. Hook up the compressor to the car, attach the needle to the nozzle, insert said needle into ball, turn on the power and pressure immediately builds to infinite (as indicated by the gauge), but the ball isn't getting any fuller. Examination of the needle reveals that it is only a hollow tube. Conventional inflation needles (at any rate, the ones I am familiar with) have a blunt, solid tip and a hole in the side of the tube a fraction of an inch from the tip of the tube. I find such a needle hiding in the secret compartment on the bottom of the compressor. Correct needle works and the ball inflates. One fat old man and one whippersnapper square off on the court. My first dozen shots were all airballs. All that could be said was that they were headed in the general direction of the basket. After I warmed up a bit I made a couple of good, on the move shots. Impressed myself, I did. But that lasted maybe 10 or 15 minutes before I was shot.

Voodoo

I originally title this post Chemistry!, but by the time I got done I had decided it needed something a little stronger.


Reaction between Bromine and Aluminum
Deliberate daughter has started a chemistry class and I am following along. Lesson 1 includes a video of Aluminum reacting with Bromine. I was surprised how much smoke was generated from the small amount of liquid. But now I want to more about this Bromine stuff. I mean you never run into it. Just what the heck is it anyway?

Periodic Table with a few elements pointed out

Note where Aluminum and Bromine reside in the Periodic Table. Aluminum is our well known friend, used to make airplanes, new Ford F-150 pickup truck bodies, beer cans and aluminum foil.

Bromine is kind of obscure. It is one of the Halogens, highly reactive gases. Florine and Chlorine are two popular examples. They are in the pink column in the above chart, right next to the Orange column at the right hand side that contains the inert gases like Helium, Argon and Neon. Only Argon is shown in the chart.

People used to use Bromine for a number of things, but most of those applications have fallen by the wayside for one reason or another. These days all it seems to be used for is

• as a disinfectant for hot tubs (like chlorine for swimming pools), 
• drilling mud (as in drilling for oil), 
• facilitating the production of other chemical compounds, and 
• Halogen lightbulbs

Halogen lightbulbs was a surprise. I had no idea. I had never even made the connection between Halogen lights and the Halogen family of elements. I think I had them confused with the inert gases. I mean they make lights using Neon and Xenon, maybe Halogen is just a fancy name for them. No, Wrong. How did I miss this?
In the video up top, Nile (that's what I'm calling him) alludes to making your own bromine, for which he has another video. We get into some real chemistry here.


Making Elemental Bromine (from household items)
"Greasing the joints with concentrated sulfuric acid". Are you freaking kidding me?  How the hell could you do something like that? This is an alien land we are dealing with.

Update two days later, made a bullet list out of the uses of bromine.

Light Bulbs

2Pack, GU10 120V 35W MR16 Q35MR16 35 watts JDR Halogen Bulb Lamp

One of the light bulbs in my brand new range hood is burned out. This is an outrage! This range hood is not even six months old! If it used regular old incandescent bulbs it would be a little annoying, but no more so than the annoyance caused by any other regular light bulb burning out somewhere in the house. But this one is some fancy-schmancy light bulb, so instead of just unscrewing the old bulb, reaching into my light bulb magazine (which is stocked with a whole bunch of regular old, 60 watt, incandescent, soft-white, light bulbs), pulling out a new bulb and screwing it in, I am faced with a Gordian knot sized problem.

It doesn't look like that big a problem, I should be able to pop the old bulb out, run to the store and buy a replacement, and pop the new one in. Not too bad. The annoyance of having to run to the store is countered by the fact that I would be going to Lowe's (a giant hardware store) which is always a soothing experience. Mmm, tools. Mmm, hardware. Mmm, plumbing. You get the picture, I hope.

But first I have to get the old bulb out, and how to do that is not obvious. The bulb is flush mounted in a panel on the underside of the hood. There is just a little lip protruding from the surface, and being coated with a thin film of grease (that comes from all the cooking being done here), it is un-grasp-able. I try a medium sized pair of channellocks, judiciously applied, to try and grip it, but no go. An observation by my sharp eyed assistant reveals arrows drawn on the panel indicating the direction the bulb should be turned to remove or install. So we are on the right track, but how do you get a hold of the bulb in order to turn it? And then inspiration hits. The bulb has a flat lower surface, flush with the panel. I reach up with my hand, place my palm flat on the lower face of bulb, apply a little pressure, turn (anti-clockwise) maybe a quarter circle, and it falls out in my hand. Easy-peasy, if you know what you are doing.

So what kind of bulb is this? Here's the second part of the problem. I can see there are some black markings on the side, but they are almost unreadable. They are printed on the outside of the glass reflector, which is fluted and plated on the inside. By focusing on one character at a time and slowly turning the bulb I can make out that it is a

GU10C

110V35W

I could take it to the store and look for one, but I have other things to do, and if I wait to do this when I am out and about I am liable to forget. Amazon to the rescue. Point and click and a couple of minutes later a pack of two bulbs is on its way for $9. It won't be here for a couple of days, but that is more reliable than relying on me to remember to look for one at the hardware store.

P.S. These bulbs come in two flavors: LED and Halogen. The one I have in my hand appears to be a Halogen bulb. I am still a little suspicious of LED's. Enthusiasm drives up the price. High prices cool my enthusiasm, so Halogen for me. Plus all the others on the first page were for packages of eight or ten, and I do not want a pile of these suckers. I only want one, but two might not be a bad idea. There are two bulbs in the hood, and if one has burned out the other might not be far behind.

Update: Plugging in the new bulb was a bit of a trick. As you can see from the photo (above), there are two prongs on back of the bulb. Plugging in the new bulb should be fairly straight forward, except once the prongs are near enough to the socket, you can no longer see what is going on. So I eyeball the situation, orient the bulb as best I can, raise it straight up and hope the prongs reach the correct holes. I make several attempts but none make the connection. Finally I abandon my careful align-the-bomb-sight method and simply push the bulb up with the palm of my hand and turn it (much in reverse of my removal procedure) and after a little big of jiggling, it pops into position. Now it's a matter of turning the bulb enough to engage the clips. That takes some repeated applications of torque, but eventually it gets done.

Freddies Comes Thru

My desk lamp quit yesterday. Didn't realize how much I depended on it until then. Set out to track down the problem and finally decided to try a new bulb. Last time I had a Halogen light fail I assumed the bulb had burned out and only after climbing up and down the ladder a couple of times did I discover that there was nothing wrong with the bulb, so I was a little hesitant to blame the bulb this time. I took the bulb out (used my #1 Phillips that I located the other day) and looked at it but there does not appear to be anything wrong: the filament looks intact. I used a VOM (Volt/Ohm Meter) to measure the resistance of across the filament and it showed it was open, but that doesn't mean much. New bulbs act the same way. Measured the voltage coming out of the wall-wart (step down transformer that plugs into the wall) and it was only a volt or two. But this wall-wart weighs practically nothing. Usually these things weigh in around half a pound. This one is only a few ounces. Must be some kind of special electronic gizmo. Probably does not deliver full voltage unless there is a real load, and a meter does not do the job. Tried another 12 Volt wall-wart on the bulb, see if I could get it to light up. That didn't work either. So we have some evidence that the bulb might be bad.

I drive over to Freddies in Cornelius. It takes a while but I eventually find the light bulb display over by the plumbing, and low and behold, they actually have a selection of halogen bulbs. Okay, now which one do I need? Fortunately I checked the output on the transformer: 12VAC & 6 Amps. Volts times amps gives 72 Watts. 60 watts looks like the right choice. 10 and 20 are too small, and the others are too big. Try to read the numbers off my old bulb, but they are tiny and I forgot my glasses. Walk around until I find the reading glasses display. I put on a pair and I am able to convince myself that I have picked the right bulb. I use the U-Scan to pay $6 for the bulb.

Back at the house I try to get the bulb out of the package and into the lamp without touching the glass. (Don't want to get any oil on it. These bulbs get really hot and rumor has it that any oil on the glass will combust and cause the glass to break/shatter/explode.) I fail on both counts. The tips of the leads on the bulb are squared off and require some finesse to get them into their holes. I wipe off the bulb with a cleanish handkerchief and turn on the power and we have light!

Each arm of this lamp is made of two parallel tubes. The rods carry the current. The lamp assembly has a pair of spikes that plug into the ends of the tubes that make up the upper arm. There are no wires, the tubes conduct the electricity.

Note about the picture: I found this image using Google. It appears to be the same as mine, though I bought mine at Costco several years for quite a bit less money. Looking at the picture I see massive jaggies on the arms on my screen, but the original looks very clean, and it is not that much bigger than this one. Curious.

Update December 2016 replaced missing picture.

Stupid LED's

CIE Standard Illuminant D65
Spectral power distribution

The future is stupid. Used to be, back in the bad old days, you could go to any grocery store and pick up a light bulb. They had a complete selection from a low of 40 watts to a high of 100 watts. The selection was complete because that was all there was. Now light bulbs have gone the way of nuts and bolts: there is a different bulb for every application. 

Chromaticity diagram by David MacAdam
also known as the CIE 1960 Color Space
D65 appears near the 8000K line
Note sure what this means, but it makes a pretty picture.

They don't just come in a different power (watts) ratings, there are different sizes, mountings, technologies, and CRI-s (Color Rendering Indexes). Remember the Wall of Diapers at Toys R Us? That's what the light bulb display at Home Depot looks like now. I spent ten minutes there the other day looking for a Halogen bulb for a work light and I could not find it. I finally had to ask someone. Took him a minute but there it was, right in the area I had been looking. Confused by the packaging I was. Must be getting old, starting to talk like Yoda I am.

Old fixture: Broan 9427P 500 Watt, 4.0 Sones, 70 CFM

We just replaced the light fixture / exhaust fan in the master bath with a new one. Nothing wrong with old one other than it was noisy. Didn't bother us when we built the house 25 years ago, but now my wife is at war with the mold growing on the ceiling (see those itsy-bitsy, teeny-weeny black spots on the ceiling?) and she wants a new exhaust fan. Normally this would be a simple fix, there are a wide variety of exhaust fans available as long as you want the standard size, which is about a foot square. Ours is not, it is a fancy-schmantzy one with two flood lights so it's about a foot by fifteen inches. We could have replaced it with a standard one, but that would have meant patching the drywall which would have turned a day long project into a week long one. Effing drywall.

New Fixture: Utilitech 7123-02-L 1300W, 1.5 Sones, 80 CFM

Looked around and found one the right size that should be quieter, but it only has room for one 60 watt light bulb and it is like turning on the dark. So I got a 100 watt equivalent LED and plugged that in. Doesn't really help, it is like turning on the dim and it's still that ugly 'cool white color'. Next step might be to replace the light fixture with a pair of LED fixtures designed for mounting in the ceiling. That's going to require some chopping and hacking to make them fit and considerable finesse so it doesn't look like a hack job.

LED 100 Watt Equivalent

After we got the fixture installed we discovered that the fan wouldn't run. Seems that the old fan had an old timey motor and it worked fine with the electronic timer, but new the fan has a fancy new motor and it required a different kind of timer. The essential difference is that the old timer did not require a neutral wire connection and the new one did.

TORK In-Wall Countdown Lighting Timer

P.S. On every other exhaust fan in the world, the bezel / grill is attached with springs so all you need to do to remove it is pull it down a bit and then reach in and disconnect the springs. The bezel on the new Utilitech exhaust fan is attached with a screw, a screw that is hidden behind the light bulb. So in order to remove the grill, you must first remove the lens, the light bulb and the screw. Now that the grill is loose, you can reach up and unplug the wire to the bulb. Now it is finally free. Bah, double bah and humbug.

P.P.S. Does the heater in the new unit work? I can't tell. I could definitely tell when the heat lamp in the old fixture was on.

Brave New World

Tried to pick up some 60 watt light bulbs at Hank's this evening. No regular incandescents to be found. This was the closest. Looked at the box, looked on the web, but I couldn't figure out what trick they were using until I picked up this image. Halogen, that's the trick. Now that I have seen it in the picture I can see it on the actual box. $8 for a pack of four. Amazon wants $6.50. I can't even tell if $2 a bulb is expensive or not. The price of light bulbs used to not even register, they were an incidental and cost so little they might as well be free. Of course, a six pack of beer used to cost $1. Now they want $10. Kwiky Mart used to only keep $20 in cash on hand. Now they keep $50.

    Speaking of beer, I've been drinking Stella Artois lately, but tonight I noticed that they have reduced the size of their bottles from 12 ounces to 11. I was suspicious when the 22 ounce bottles started showing up. Now my suspicions are confirmed. The anti-fun people are still trying to put the screws to us, one ounce at a time.

     And Finally is still trying to get their bulb to market. Previous post on the subject.

2006 Mitsubishi Endeavor Brake Light Replacement

Brake light burned out on Mom's car, so I replaced it. The only trick was getting the light fixture loose from the body. Open the lift gate and two Phillips head screws are revealed. Removing them loosens the inside edge, but the outside edge is still firmly attached. A little wiggling and a little gentle tugging and it comes loose. There are two studs that snap into little plastic retainers in the body. The studs have grooves just below the tip that give the retainers someplace to grip. Just pull straight out and they will come loose. Take the screws out first, of course.

I realize the picture angle is a little strange. We are looking down and forward from in back of the left hand rear turn signal fixture. The bulb hanging there is the brake light/taillight. The top of the bumper is visible in the lower right corner.

• Red arrows mark the studs,
• Green arrows their sockets in the bodywork.
• Purple arrows mark the screw holes in the light fixture,
• Purple circle marks the upper screw socket in the bodywork.

I had to replace both headlamp bulbs last year. Now I am wondering how long the other brake light is going to last. My truck is seven years older than this vehicle and I haven't had to replace any light bulbs, at least not that I recall. Kind of weird. I would think a truck would be a harsher ride for light bulbs than a passenger vehicle.

Another oddity is that the headlamp bulbs on this car are the fancy new halogen bulbs with their plastic fittings, but these brake light bulbs are from like the 1950's, standard old 1157's.

Update December 2016 replaced missing picture.

Colored Lights

Boeing B-52 Cockpit

At night the military uses red light to illuminate instruments on all kinds of equipment: aircraft, ships, vehicles, radar, what-have-you, the reason being that it has the least effect on your night vision. When we got our 2006 Mitsubishi Endeavor, I was disappointed to find that it had blue indicator lights on the dash. I suppose that was the fashion back then, and I guess it doesn't matter so much in a car, after all you've nice bright halogen bulbs to illuminate the road, so your night vision's probably worth shit anyway, so the color of the indicator lights isn't going to make any difference.

Audi S4 Cockpit

    Tonight I got a ride in a new Audi S4 and it had red marker lights all over the dash. They were not the kind of subdued red you see in military equipment, it was more of a a candy-apple, in-your-face, high fashion kind of red. Can't really tell from the difference from these pictures since they have been translated to bits and then reconstituted using the RGB pixels in your monitor. The original colors in the Audi are probably not even really red, probably made of ultraviolet crossed with infrared to give the illusion of red. The fashion in dashboard lights has changed. Imagine that.
    Recently someone was trying to justify using blue lights in the instruments. Our eyes have two kinds of cells that detect light: rods and cones. Cones are used for normal, daylight color vision. Rods are used for black and white, low light (nighttime) vision. Rods are sensitive to blue light, but insensitive to red light. So blue will work at night, and you should be able to get by with much dimmer blue lights than if you used red, but using red lights will not impact your night vision.

Desk Light

This looks like my Dell keyboard, mostly. If it was the same size it would probably work, but how do you know if it is or not? And how much difference would be significant?

The light on my desk is getting old and the switch is getting cranky. It has a halogen bulb and the shade has no vent so it gets very hot and over the years it has baked the switch housing into near failure. The rest of the lamp is fine, it's just the switch that is failing. I would replace the switch if I could find one, but locating such an animal promises to be a trip down the proverbial rabbit hole, so I've just kind of been limping along.
     Since the switch is unreliable I often find myself typing in the dark which is fine until my fingers lose their place and then when I look down to regain my place I can't see the labels on the keys. This has led me to conclude that all I might really need is a light for my keyboard. I was thinking something low profile that clips along the top edge and casts a 'warm glow' over the keys making the labels readily discernible. No such animal exists. All we have is these little bitty 'book light' things. They might work, but I don't want some mechanical snake sticking his head into my viewspace.
    OK, how about a backlit keyboard? Well, that might work, if it was cheap enough. Keyboards from the recycler cost $3, so I'm not prepared to shell out $80 just to get a little light. Amazon has some for around $20, which is more than a buck and half, but feasible.
    But now we have another problem. Do any of these backlit keyboards have EXACTLY the same layout as the Dell keyboard I have been using for the last decade? The last thing I need right now is to have to adjust to a new keyboard. Plus there are several other computers here that all have Dell keyboards. I might be willing to shell out $20 for one keyboard, but I am certainly not going to replace all of my keyboards. Besides, some of the other people here might be even more resistant to change than I am.
    So, do these backlit keyboards have the same layout as a Dell or not? No way to tell. They certainly don't tell you, and I'm not sure looking at pictures would be enough. Yes, it looks the same, but what if the all the keys are a slightly different size, or that one key you use all the time that is off in the corner is in a slightly different location, just different enough that your finger glances off the side instead of catching the edge and you have to pause and deliberately restrike that one stinking key. That would suck.
    But hey! Maybe Dell sells backlit keyboards. They might, but I didn't find any.
    Where is the Association for Keyboard Layout Certification when you need them?